httk property definitionsProperty definitions using the OPTIMADE property definition format, hosted by httk
v0.1
datasets
Point groups (property) - https://schemas.httk.org/defs/v0.1/datasets/pointgroups
Ordered table of crystallographic point-group records. Each item contains point-group classification, finite point-group operations, conjugacy classes, and real and complex character tables generated from cctbx and spgrep.
Space groups (property) - https://schemas.httk.org/defs/v0.1/datasets/spacegroups
Ordered table of crystallographic space-group setting records.
Each item describes one concrete Hall/International Tables setting of a space group, including symbols, classifications, symmetry operations, asymmetric-unit information, Wyckoff positions, and related auxiliary data.
The companion top-level indicies.index_hall_entry_to_spacegroups lookup maps normalized Hall entries to indices in this list; it is not an OPTIMADE property.
Transformations (property) - https://schemas.httk.org/defs/v0.1/datasets/transformations
Ordered table of crystallographic transformation records.
Each item describes transformations and normalizer information for one concrete International Tables H-M entry.
In transformations_hm_entry.json.gz, items are keyed for lookup by the companion top-level indicies.index_hm_entry_to_transformations_per_hm_entry object; that index is not an OPTIMADE property.
derivations
Bias ([unknown]) - https://schemas.httk.org/defs/v0.1/derivations/bias
The mean signed residual of the base property, predicted minus reference unless stated otherwise. The derivation term applies to a base property definition identified alongside; the value has the base property's unit and shape.
Mean absolute error ([unknown]) - https://schemas.httk.org/defs/v0.1/derivations/mae
The mean of the absolute residuals of the base property, predicted minus reference unless stated otherwise. The derivation term applies to a base property definition identified alongside; the value has the base property's unit and shape.
Maximum absolute error ([unknown]) - https://schemas.httk.org/defs/v0.1/derivations/maximum_absolute_error
The maximum of the absolute residuals of the base property, predicted minus reference unless stated otherwise. The derivation term applies to a base property definition identified alongside; the value has the base property's unit and shape.
Mean ([unknown]) - https://schemas.httk.org/defs/v0.1/derivations/mean
The arithmetic mean of independent estimates of the base property. The derivation term applies to a base property definition identified alongside; the value has the base property's unit and shape.
Root-mean-square error ([unknown]) - https://schemas.httk.org/defs/v0.1/derivations/rmse
The root-mean-square of the signed residuals of the base property, predicted minus reference unless stated otherwise. The derivation term applies to a base property definition identified alongside; the value has the base property's unit and shape.
Standard deviation ([unknown]) - https://schemas.httk.org/defs/v0.1/derivations/standard_deviation
The sample standard deviation of estimates of the base property, with the degrees-of-freedom correction (ddof) as recorded by the producer. The derivation term applies to a base property definition identified alongside; the value has the base property's unit and shape.
Standard error ([unknown]) - https://schemas.httk.org/defs/v0.1/derivations/standard_error
The standard error of an estimate of the base property: the sample standard deviation of independent estimates divided by the square root of their count. Independence of the estimates is the producer's responsibility. The derivation term applies to a base property definition identified alongside; the value has the base property's unit and shape.
entrytypes
httk point group symmetry fields (entrytype) - https://schemas.httk.org/defs/v0.1/entrytypes/pointgroups
httk records entry type (entrytype) - https://schemas.httk.org/defs/v0.1/entrytypes/records
A records entry carries the value of one formally declared property (a computed or measured quantity) as its own entry, so that multiple parallel determinations of the same quantity for the same system can coexist as separate entries linked via provenance relationships. The value properties served on this entry type are declared per provider through property definitions and are not enumerated here.
httk runs entry type (entrytype) - https://schemas.httk.org/defs/v0.1/entrytypes/runs
A runs entry represents one specific, individual execution of a workflow or process that consumed and/or produced other entries. Provenance edges (inputs, artifacts, outputs) are expressed as relationships, not properties.
httk space group symmetry fields (entrytype) - https://schemas.httk.org/defs/v0.1/entrytypes/spacegroups
httk transformation fields (entrytype) - https://schemas.httk.org/defs/v0.1/entrytypes/transformations
properties
chemistry
Species constituent charges (property) - https://schemas.httk.org/defs/v0.1/properties/chemistry/species_charges
The explicitly assigned charge of each constituent of a species, as a dimensionless charge number, i.e., the charge in units of the elementary charge.
Species constituent labels (property) - https://schemas.httk.org/defs/v0.1/properties/chemistry/species_labels
A free-form label attached to each constituent of a species.
Species constituent spins (property) - https://schemas.httk.org/defs/v0.1/properties/chemistry/species_spins
The idealized spin assigned to each constituent of a species, as a dimensionless signed number.
Structure charge (property) - https://schemas.httk.org/defs/v0.1/properties/chemistry/structure_charge
The explicitly assigned net charge of the whole structure, as a dimensionless charge number, i.e., the charge in units of the elementary charge.
core
Atomic force (property) - https://schemas.httk.org/defs/v0.1/properties/core/atomic_force
The force on one atom (the negative gradient of the energy with respect to the position of the atom), in electronvolt per angstrom, as a vector over dim_spatial in the Cartesian frame of the structure it belongs to.
This property is the base of force statistics: a statistic of it (such as an error or a bias over a population of atoms) has the same shape, one value per Cartesian component.
A null value means the quantity is not available or not recorded.
Average total energy (property) - https://schemas.httk.org/defs/v0.1/properties/core/average_total_energy
The total energy of a simulated system averaged over the time evolution of a molecular dynamics run, in electronvolt. It is the average the simulation code reports for the run where the code prints one (for example the averages table of a GROMACS md.log); otherwise it is the arithmetic mean of the total energies the code printed over the run's sampled steps. The averaging window, the sampling interval and the ensemble are determined by the run, so values are comparable only between runs with the same protocol. The value is for the whole simulated system, kinetic plus potential energy. The reference/zero of the total energy scale is method-, force-field- and code-specific, so values are comparable only within one consistent computational setup.
Cartesian site forces (property) - https://schemas.httk.org/defs/v0.1/properties/core/cartesian_site_forces
The force on every site of a structure (the negative gradient of the total energy with respect to the Cartesian position of each site), in electronvolt per angstrom.
Enthalpy (property) - https://schemas.httk.org/defs/v0.1/properties/core/enthalpy
The enthalpy H = E_total + P V in electronvolt, with P the applied (external) pressure and V the cell volume. Extensive: refers to the whole simulated cell, not per atom. The reference/zero of the energy scale is method- and code-specific, so values are comparable only within one consistent computational setup. A null value means the quantity is not available or not recorded.
run finish time (property) - https://schemas.httk.org/defs/v0.1/properties/core/finished_at
When the run finished: for httk-workflow jobs, the end of the last attempt of the job, as a timezone-aware timestamp.
Fraction (property) - https://schemas.httk.org/defs/v0.1/properties/core/fraction
A numerical representation formed as the quotient of two numbers represented as a string.
Fractional coordinate precision (property) - https://schemas.httk.org/defs/v0.1/properties/core/fractional_coordinate_precision
The absolute precision of a set of fractional coordinates, in fractional units.
Kinetic energy (property) - https://schemas.httk.org/defs/v0.1/properties/core/kinetic_energy
The nuclear kinetic energy of a system, in electronvolt. Extensive: refers to the whole simulated cell, not per atom. A null value means the quantity is not available or not recorded.
Length precision (property) - https://schemas.httk.org/defs/v0.1/properties/core/length_precision
The absolute precision of a stated length, in ångström.
name (property) - https://schemas.httk.org/defs/v0.1/properties/core/name
A human-readable name of the entry.
Potential energy (property) - https://schemas.httk.org/defs/v0.1/properties/core/potential_energy
The potential energy of a computed system from the energy model, in electronvolt. Extensive: refers to the whole simulated cell, not per atom. The reference/zero of the energy scale is method- and code-specific, so values are comparable only within one consistent computational setup. A null value means the quantity is not available or not recorded.
Pressure (property) - https://schemas.httk.org/defs/v0.1/properties/core/pressure
The pressure of a system, in gigapascal (GPa; 1 GPa = 10^9 Pa). Pressure is positive in compression; stress is tensile-positive. For a hydrostatic state P = -tr(sigma)/3. A null value means the quantity is not available or not recorded.
source ID (property) - https://schemas.httk.org/defs/v0.1/properties/core/source_id
The run's identifier in the system that executed it. For httk-workflow jobs, this is the workspace and job identity in the form
run start time (property) - https://schemas.httk.org/defs/v0.1/properties/core/started_at
When the run started: for httk-workflow jobs, the start of the first attempt of the job, as a timezone-aware timestamp.
Stress tensor (property) - https://schemas.httk.org/defs/v0.1/properties/core/stress_tensor
The stress tensor of a system in Voigt notation, in gigapascal (GPa). Pressure is positive in compression; stress is tensile-positive. Voigt order [xx, yy, zz, yz, xz, xy]. A null value means the quantity is not available or not recorded.
String markups (property) - https://schemas.httk.org/defs/v0.1/properties/core/string_markups
Strings with alternate markup and/or encoding for display rendering.
Temperature (property) - https://schemas.httk.org/defs/v0.1/properties/core/temperature
The temperature of a system, in kelvin. A null value means the quantity is not available or not recorded.
Total energy (property) - https://schemas.httk.org/defs/v0.1/properties/core/total_energy
The total energy of a computed system as produced by a calculation, in electronvolt. The reference/zero of the total energy scale is method- and code-specific, so values are comparable only within one consistent computational setup.
Volume (property) - https://schemas.httk.org/defs/v0.1/properties/core/volume
The volume of the simulation cell, in cubic angstrom. Extensive: refers to the whole simulated cell, not per atom. A null value means the quantity is not available or not recorded.
Workflow declaration URI (property) - https://schemas.httk.org/defs/v0.1/properties/core/workflow_declaration_uri
A URI identifying the workflow declaration (the reusable process definition, as opposed to a specific execution) behind a runs entry. No particular URI scheme, resolvability, or formalism is mandated. Providers wanting two runs recognized as executions of the same declaration MUST use an identical URI. Null is expected for ad-hoc scripts, interactive executions, and legacy data with no formal workflow identifier.
Workflow definition URI (property) - https://schemas.httk.org/defs/v0.1/properties/core/workflow_definition_uri
A URI identifying the workflow definition (the code that ran) behind a runs entry, as opposed to the workflow declaration identified by workflow_declaration_uri.
A typical value is a git URI pinned to a full commit hash, of the form git+https://host/path@<commit>#<subdir>.
No particular URI scheme or resolvability is mandated, but providers SHOULD use a URI that pins the exact code revision.
Null is expected when the executed code is unknown, e.g., for legacy data.
defects
Adsorption energy (property) - https://schemas.httk.org/defs/v0.1/properties/defects/adsorption_energy
The adsorption energy E_ads = E(substrate+adsorbate) - E(substrate) - sum_i n_i E_ref,i, in electronvolt, with n_i the numbers of adsorbed atoms or molecules and E_ref,i their reference energies. Negative values mean favourable adsorption. A null value means the quantity is not available or not recorded.
Charge transition level (property) - https://schemas.httk.org/defs/v0.1/properties/defects/charge_transition_level
The charge transition level q/q' of one defect, in electronvolt: the Fermi level (relative to the valence-band maximum) at which the formation energies of the two charge states are equal. For a single defect it is independent of the chemical potentials. A null value means the quantity is not available or not recorded.
Charged defect formation energy (property) - https://schemas.httk.org/defs/v0.1/properties/defects/charged_defect_formation_energy
The formation energy of a charged point defect in one charge state, in electronvolt, together with all quantities that entered it. List members elements, atom_changes and chemical_potentials are parallel lists sharing the dimension _httk_dim_elements, since dictionaries cannot have free-form keys; they MUST have equal length.
E_f = E_def - E_host - sum_i n_i mu_i + q (E_F + E_VBM + dV) + E_corr.
A null value means the quantity is not available or not recorded.
Segregation energy (property) - https://schemas.httk.org/defs/v0.1/properties/defects/segregation_energy
The segregation energy of a solute, in electronvolt: E(solute at the target site) - E(solute in a bulk-like reference site). Negative values mean that segregation to the target site is favoured. A null value means the quantity is not available or not recorded.
Surface energy (property) - https://schemas.httk.org/defs/v0.1/properties/defects/surface_energy
The surface energy gamma = (E_slab - N E_bulk - sum_i dn_i mu_i) / A_total, in joule per square metre (J m^-2), with E_bulk the bulk energy per formula-unit-or-atom counted by N, dn_i the excess number of atoms of species i and mu_i their chemical potentials. A_total is the total exposed area: both faces of a symmetric slab are counted. A null value means the quantity is not available or not recorded.
dynamics
Distinct van Hove function (property) - https://schemas.httk.org/defs/v0.1/properties/dynamics/distinct_van_hove_function
Distinct van Hove function G_d(r,t) at one lag: the density per volume of distinct atoms j at displacement r from the position of atom i at time origin t0 to that of j at t0 + t, with i != j, using minimum images in a fixed fully periodic cell.
Intermediate scattering function (property) - https://schemas.httk.org/defs/v0.1/properties/dynamics/intermediate_scattering_function
Coherent intermediate scattering function F(q,t) =
Self intermediate scattering function (property) - https://schemas.httk.org/defs/v0.1/properties/dynamics/self_intermediate_scattering_function
Self intermediate scattering function F_s(q,t) = mean over atoms and time origins t0 of exp(i q . [r(t0 + t) - r(t0)]), with q the Cartesian wavevector (2 pi included) and r the unwrapped position of an atom; F_s(q,0) = 1.
Self van Hove function (property) - https://schemas.httk.org/defs/v0.1/properties/dynamics/self_van_hove_function
Self van Hove function G_s(r,t) at one lag: the probability density per volume of the displacement of a single atom over the lag, binned in the displacement length r (spherical shells).
Velocity power spectrum (property) - https://schemas.httk.org/defs/v0.1/properties/dynamics/velocity_power_spectrum
Velocity power spectrum of a trajectory: a one-sided periodogram of the atomic velocities, not a normalized phonon density of states.
electronic
Band gap (property) - https://schemas.httk.org/defs/v0.1/properties/electronic/band_gap
The fundamental band gap in electronvolt: CBM - VBM over the sampled k-points, determined from occupations; indirect gaps are allowed. A metal is represented by the value 0. A null value means the quantity is not available or not recorded.
Born effective charges (property) - https://schemas.httk.org/defs/v0.1/properties/electronic/born_effective_charges
The Born effective charge tensors of the sites of the referenced structure, in units of the elementary charge e.
DFT band gap (property) - https://schemas.httk.org/defs/v0.1/properties/electronic/dft_band_gap
The Kohn-Sham band gap of a material from a density-functional-theory (DFT) calculation, given in electronvolts. Its value depends on the computational method and exchange-correlation functional used.
Direct band gap (property) - https://schemas.httk.org/defs/v0.1/properties/electronic/direct_band_gap
The direct band gap in electronvolt: the minimum over the sampled k-points of the CBM - VBM separation at the same k-point, determined from occupations. A metal is represented by the value 0. A null value means the quantity is not available or not recorded.
Electronic band structure (property) - https://schemas.httk.org/defs/v0.1/properties/electronic/electronic_band_structure
Electronic band energies of the referenced structure along a path of k-points through the Brillouin zone (a line-mode band structure).
Electronic density of states (property) - https://schemas.httk.org/defs/v0.1/properties/electronic/electronic_density_of_states
Electronic density of states of a simulation cell.
Fermi energy (property) - https://schemas.httk.org/defs/v0.1/properties/electronic/fermi_energy
The Fermi energy of a calculation, in electronvolt, on the absolute energy scale of that calculation (the same scale as its eigenvalues and total energy). The reference of that scale is method- and code-specific, so values are comparable only within one consistent computational setup. A null value means the quantity is not available or not recorded.
High-frequency relative permittivity (property) - https://schemas.httk.org/defs/v0.1/properties/electronic/high_frequency_relative_permittivity
The high-frequency relative permittivity, dimensionless, as the isotropic mean (trace/3) of the high-frequency relative-permittivity tensor, which is the electronic contribution at clamped ions (ions held fixed). A null value means the quantity is not available or not recorded.
Relative effective mass (property) - https://schemas.httk.org/defs/v0.1/properties/electronic/relative_effective_mass
The effective-mass tensor of one band at the wavevector center, relative to the free-electron mass: m*/m_e = m_e^-1 hbar^2 (d^2E/dk_i dk_j)^-1, the inverse of the band-energy curvature matrix at center. center is in angstrom^-1 (2 pi included); tensor is dimensionless.
The tensor is signed: negative values correspond to hole-like (downward) curvature, and mixed-sign eigenvalues occur at saddle points. Where the curvature matrix is singular the effective mass is undefined and the value is null.
A null value means the quantity is not available or not recorded.
Spin-channel electronic density of states (property) - https://schemas.httk.org/defs/v0.1/properties/electronic/spin_channel_electronic_density_of_states
Electronic density of states of a simulation cell in one collinear spin channel.
Static relative permittivity (property) - https://schemas.httk.org/defs/v0.1/properties/electronic/static_relative_permittivity
The static relative permittivity (dielectric constant), dimensionless, as the isotropic mean (trace/3) of the static relative-permittivity tensor, which includes both the ionic and the electronic contributions. A null value means the quantity is not available or not recorded.
energetics
Chemical potential region (property) - https://schemas.httk.org/defs/v0.1/properties/energetics/chemical_potential_region
Linear constraints defining the allowed region of absolute per-atom chemical potentials mu_i of a host compound against competing phases.
Convex-hull phase diagram (property) - https://schemas.httk.org/defs/v0.1/properties/energetics/convex_hull_phase_diagram
A convex-hull phase diagram over a set of phases with known energies.
Energy above hull per atom (property) - https://schemas.httk.org/defs/v0.1/properties/energetics/energy_above_hull_per_atom
The nonnegative per-atom energy distance, in electronvolt, of a phase to the lower convex hull of the competing phases considered; zero for a phase on the hull. The set of competing phases is part of the producing analysis. A null value means the quantity is not available or not recorded.
Formation energy per atom (property) - https://schemas.httk.org/defs/v0.1/properties/energetics/formation_energy_per_atom
The formation energy per atom, (E - sum_i n_i mu_i)/N in electronvolt, with E the total energy of the cell, n_i the number of atoms of element i, mu_i the elemental reservoir chemical potential per atom and N the total number of atoms. The references mu_i are part of the producing analysis and recorded alongside. The reference/zero of the energy scale is method- and code-specific, so values are comparable only within one consistent computational setup. A null value means the quantity is not available or not recorded.
Reaction energy (property) - https://schemas.httk.org/defs/v0.1/properties/energetics/reaction_energy
The energy of a reaction in electronvolt, products minus reactants for the balanced reaction as written, weighted by the stoichiometric coefficients of that reaction. Extensive in those coefficients: it refers to the reaction as written, not per atom. A null value means the quantity is not available or not recorded.
Total energy per atom (property) - https://schemas.httk.org/defs/v0.1/properties/energetics/total_energy_per_atom
The total energy of the cell divided by the number of atoms in the cell, in electronvolt. The reference/zero of the energy scale is method- and code-specific, as for the total energy, so values are comparable only within one consistent computational setup. A null value means the quantity is not available or not recorded.
kinetics
Activation energy (property) - https://schemas.httk.org/defs/v0.1/properties/kinetics/activation_energy
The Arrhenius activation energy E_a, in electronvolt, obtained from the slope of ln k against 1/T (k = A exp(-E_a / (k_B T))). A null value means the quantity is not available or not recorded.
Arrhenius prefactor (property) - https://schemas.httk.org/defs/v0.1/properties/kinetics/arrhenius_prefactor
The Arrhenius prefactor A, in inverse seconds, of a first-order rate constant k = A exp(-E_a / (k_B T)), for example a jump frequency; E_a is the activation_energy.
A null value means the quantity is not available or not recorded.
Forward migration barrier (property) - https://schemas.httk.org/defs/v0.1/properties/kinetics/migration_barrier_forward
The forward migration barrier of a sampled minimum-energy path, in electronvolt: the highest sampled image energy minus the energy of the initial image. No interpolation between images is applied. A null value means the quantity is not available or not recorded.
Reverse migration barrier (property) - https://schemas.httk.org/defs/v0.1/properties/kinetics/migration_barrier_reverse
The reverse migration barrier of a sampled minimum-energy path, in electronvolt: the highest sampled image energy minus the energy of the final image. No interpolation between images is applied. A null value means the quantity is not available or not recorded.
magnetism
MAGNDATA identifiers (property) - https://schemas.httk.org/defs/v0.1/properties/magnetism/magndata_ids
The identifiers of MAGNDATA magnetic-structure entries associated with a material.
Magnetic space group (BNS) (property) - https://schemas.httk.org/defs/v0.1/properties/magnetism/magnetic_space_group_bns
The magnetic space group of a material in Belov-Neronova-Smirnova (BNS) notation.
Site magnetic moments (property) - https://schemas.httk.org/defs/v0.1/properties/magnetism/site_moments
The magnetic moment vector of each site, in Cartesian coordinates and Bohr magnetons.
Total magnetic moment (property) - https://schemas.httk.org/defs/v0.1/properties/magnetism/total_magnetic_moment
The total magnetic moment of the cell, in Bohr magnetons, as a vector over dim_spatial: the vector sum of the site moments in the Cartesian frame of the structure (the frame of lattice_vectors and cartesian_site_positions).
Only the sum of the site moments is recorded; contributions outside the sites (interstitial regions) are not included unless the producing analysis states so.
A null value means the quantity is not available or not recorded.
mechanics
Bulk modulus (property) - https://schemas.httk.org/defs/v0.1/properties/mechanics/bulk_modulus
The bulk modulus B = -V dP/dV at the reference state, in gigapascal. The protocol that produced the value (static equation-of-state fit, quasi-harmonic at temperature T, elastic-tensor average) is identified by how it was produced and recorded alongside, not by this definition. A null value means the quantity is not available or not recorded.
Bulk modulus (Hill) (property) - https://schemas.httk.org/defs/v0.1/properties/mechanics/bulk_modulus_hill
The Hill polycrystalline-average bulk modulus from the elastic tensor, in gigapascal: K_H = (K_V + K_R)/2. Elastic stiffness relates tensor stress to ENGINEERING shear strain (gamma = 2 epsilon), so that sigma_i = C_ij e_j in Voigt form; compliance S = C^-1 in the same convention (S includes the factors 2 and 4 for shear components relative to the tensor compliance). A null value means the quantity is not available or not recorded.
Bulk modulus pressure derivative (property) - https://schemas.httk.org/defs/v0.1/properties/mechanics/bulk_modulus_pressure_derivative
The pressure derivative of the bulk modulus, B' = dB/dP at the reference state (dimensionless). A null value means the quantity is not available or not recorded.
Bulk modulus (Reuss) (property) - https://schemas.httk.org/defs/v0.1/properties/mechanics/bulk_modulus_reuss
The Reuss polycrystalline-average bulk modulus from the elastic tensor, in gigapascal: K_R = 1/[(S11+S22+S33) + 2(S12+S13+S23)], with S the compliance tensor. Elastic stiffness relates tensor stress to ENGINEERING shear strain (gamma = 2 epsilon), so that sigma_i = C_ij e_j in Voigt form; compliance S = C^-1 in the same convention (S includes the factors 2 and 4 for shear components relative to the tensor compliance). A null value means the quantity is not available or not recorded.
Bulk modulus (Voigt) (property) - https://schemas.httk.org/defs/v0.1/properties/mechanics/bulk_modulus_voigt
The Voigt polycrystalline-average bulk modulus from the elastic tensor, in gigapascal: K_V = [(C11+C22+C33) + 2(C12+C13+C23)]/9, with C the elastic tensor. Elastic stiffness relates tensor stress to ENGINEERING shear strain (gamma = 2 epsilon), so that sigma_i = C_ij e_j in Voigt form; compliance S = C^-1 in the same convention (S includes the factors 2 and 4 for shear components relative to the tensor compliance). A null value means the quantity is not available or not recorded.
Compliance tensor (property) - https://schemas.httk.org/defs/v0.1/properties/mechanics/compliance_tensor
The 6x6 elastic compliance tensor S = C^-1 in Voigt notation, in inverse gigapascal; symmetric. Rows and columns follow Voigt order [xx, yy, zz, yz, xz, xy]. Elastic stiffness relates tensor stress to ENGINEERING shear strain (gamma = 2 epsilon), so that sigma_i = C_ij e_j in Voigt form; compliance S = C^-1 in the same convention (S includes the factors 2 and 4 for shear components relative to the tensor compliance). A null value means the quantity is not available or not recorded.
Elastic tensor (property) - https://schemas.httk.org/defs/v0.1/properties/mechanics/elastic_tensor
The 6x6 elastic stiffness tensor C in Voigt notation, in gigapascal; symmetric. Rows and columns follow Voigt order [xx, yy, zz, yz, xz, xy]. Elastic stiffness relates tensor stress to ENGINEERING shear strain (gamma = 2 epsilon), so that sigma_i = C_ij e_j in Voigt form; compliance S = C^-1 in the same convention (S includes the factors 2 and 4 for shear components relative to the tensor compliance).
The components refer to the Cartesian frame of the referenced structure (the entry the record is a product of), that is the frame of its lattice_vectors and cartesian_site_positions; no IEEE standard orientation is applied.
At finite pressure this is the stress-strain coefficient tensor (Wallace's B), and stability tests on it use positive definiteness directly.
A null value means the quantity is not available or not recorded.
Equilibrium energy (property) - https://schemas.httk.org/defs/v0.1/properties/mechanics/equilibrium_energy
The minimum of the fitted energy, in electronvolt. Extensive: refers to the whole simulated cell, not per atom. The reference/zero of the energy scale is method- and code-specific, so values are comparable only within one consistent computational setup. A null value means the quantity is not available or not recorded.
Equilibrium volume (property) - https://schemas.httk.org/defs/v0.1/properties/mechanics/equilibrium_volume
The volume that minimizes the fitted energy or free energy, in cubic angstrom. Extensive: refers to the whole simulated cell, not per atom. A null value means the quantity is not available or not recorded.
Piezoelectric tensor (property) - https://schemas.httk.org/defs/v0.1/properties/mechanics/piezoelectric_tensor
The piezoelectric stress tensor e of the referenced structure in Voigt notation, in coulomb per square metre.
Shear modulus (Hill) (property) - https://schemas.httk.org/defs/v0.1/properties/mechanics/shear_modulus_hill
The Hill polycrystalline-average shear modulus from the elastic tensor, in gigapascal: G_H = (G_V + G_R)/2. Elastic stiffness relates tensor stress to ENGINEERING shear strain (gamma = 2 epsilon), so that sigma_i = C_ij e_j in Voigt form; compliance S = C^-1 in the same convention (S includes the factors 2 and 4 for shear components relative to the tensor compliance). A null value means the quantity is not available or not recorded.
Shear modulus (Reuss) (property) - https://schemas.httk.org/defs/v0.1/properties/mechanics/shear_modulus_reuss
The Reuss polycrystalline-average shear modulus from the elastic tensor, in gigapascal: G_R = 15/[4(S11+S22+S33) - 4(S12+S13+S23) + 3(S44+S55+S66)], with S the compliance tensor. Elastic stiffness relates tensor stress to ENGINEERING shear strain (gamma = 2 epsilon), so that sigma_i = C_ij e_j in Voigt form; compliance S = C^-1 in the same convention (S includes the factors 2 and 4 for shear components relative to the tensor compliance). A null value means the quantity is not available or not recorded.
Shear modulus (Voigt) (property) - https://schemas.httk.org/defs/v0.1/properties/mechanics/shear_modulus_voigt
The Voigt polycrystalline-average shear modulus from the elastic tensor, in gigapascal: G_V = [(C11+C22+C33) - (C12+C13+C23) + 3(C44+C55+C66)]/15, with C the elastic tensor. Elastic stiffness relates tensor stress to ENGINEERING shear strain (gamma = 2 epsilon), so that sigma_i = C_ij e_j in Voigt form; compliance S = C^-1 in the same convention (S includes the factors 2 and 4 for shear components relative to the tensor compliance). A null value means the quantity is not available or not recorded.
Universal anisotropy index (property) - https://schemas.httk.org/defs/v0.1/properties/mechanics/universal_anisotropy_index
The universal elastic anisotropy index A^U = 5 G_V/G_R + K_V/K_R - 6 (dimensionless); zero for an elastically isotropic crystal. A null value means the quantity is not available or not recorded.
pointgroups
Complex character table (property) - https://schemas.httk.org/defs/v0.1/properties/pointgroups/character_table_complex
Complex irreducible character table of the crystallographic point group.
Real character table (property) - https://schemas.httk.org/defs/v0.1/properties/pointgroups/character_table_real
Real irreducible character table of the crystallographic point group.
Conjugacy classes (property) - https://schemas.httk.org/defs/v0.1/properties/pointgroups/conjugacy_classes
Conjugacy classes of a crystallographic point group.
Crystal system (property) - https://schemas.httk.org/defs/v0.1/properties/pointgroups/crystal_system
The crystal system of the space group or point group.
Hermann-Mauguin symbol (property) - https://schemas.httk.org/defs/v0.1/properties/pointgroups/hm_symbol
Hermann-Mauguin point-group symbol used as the key and display symbol for a point-group record.
is centrosymmetric (property) - https://schemas.httk.org/defs/v0.1/properties/pointgroups/is_centrosymmetric
Boolean flag indicating whether the point group contains inversion symmetry.
Laue class (property) - https://schemas.httk.org/defs/v0.1/properties/pointgroups/laue_class
The Laue class associated with the space group or point group.
Number of conjugacy classes (property) - https://schemas.httk.org/defs/v0.1/properties/pointgroups/n_conjugacy_classes
Number of conjugacy classes in the crystallographic point group.
Number of point-group operations (property) - https://schemas.httk.org/defs/v0.1/properties/pointgroups/n_pointgroup_symops
Number of point-group symmetry operations.
Order of the point group (property) - https://schemas.httk.org/defs/v0.1/properties/pointgroups/order
Order of the point group, i.e. the number of operations in the finite point group.
Schoenflies symbol (property) - https://schemas.httk.org/defs/v0.1/properties/pointgroups/schoenflies
The Schoenflies symbol for the crystallographic point group.
Schoenflies symbol markups (property) - https://schemas.httk.org/defs/v0.1/properties/pointgroups/schoenflies_markup
Display-oriented renderings of the Schoenflies symbol in schoenflies.
The plain string value is stored in the corresponding unsuffixed property; this object only provides alternate markup forms for display.
Symmetry operations (property) - https://schemas.httk.org/defs/v0.1/properties/pointgroups/symops
Full list of symmetry-operation descriptors for a point group.
Each list member is an op object as defined by /defs/v0.1/properties/symmetry/op.
Point-group operations have a zero translation part, so the screw_glide and origin_shift classification fields are omitted.
spacegroups
Asymmetric unit (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/asu
Direct-space asymmetric unit for the space-group setting, represented as a bounded non-recursive set of half-space cuts and boundary ownership rules.
Asymmetric-unit cut (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/asu_cut
One serialized asymmetric-unit half-space cut or logical cut expression in the recursive cctbx source representation.
Asymmetric unit markups (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/asu_markup
Display-oriented renderings of the plain-string asymmetric-unit restrictions in asu_str.
Shape-only asymmetric unit markups (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/asu_shape_only_markup
Display-oriented renderings of the plain-string shape-only asymmetric-unit restrictions in asu_shape_only_str.
Shape-only asymmetric unit string (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/asu_shape_only_str
Plain string rendering of the geometric shape part of the asymmetric-unit restrictions, without conditional refinements.
Asymmetric unit string (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/asu_str
Plain string rendering of the asymmetric-unit restrictions for the space-group setting.
Bravais type (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/bravais_type
The Bravais type of the translational lattice.
cctbx FFT grid factors (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/cctbx_fft_grid_factors
FFT grid-factor requirements derived from cctbx for the space group, its structure seminvariants, and its Euclidean normalizer.
Centering translations (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/centering_translations
Centering translations of the conventional cell.
Centring type (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/centring_type
The lattice centring symbol for the crystallographic setting.
Crystal system (property) - https://schemas.httk.org/defs/v0.1/properties/pointgroups/crystal_system
The crystal system of the space group or point group.
Hall symbol (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hall
The Hall symbol for a crystallographic space-group setting.
Hall symbol aliases (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hall_aliases
Alternate ASCII Hall symbols or Hall-setting keys associated with the same generated setting.
Hall alias markups (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hall_aliases_markup
Display-oriented renderings corresponding element-by-element to the alternate Hall symbols in hall_aliases.
Hall entry (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hall_entry
Normalized Hall-table entry key used internally by the generated datasets.
Hall symbol markups (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hall_markup
Display-oriented renderings of the Hall symbol in hall.
Harker planes (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/harker_planes
Harker planes of the space group in fractional Patterson coordinates.
Universal cctbx Hermann-Mauguin symbol (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_cctbx_universal
Universal Hermann-Mauguin symbol returned by cctbx for this setting.
Hermann-Mauguin entry (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_entry
The Hermann-Mauguin entry label for a conventional space-group setting from table A1.4.2.7 of the International Tables for Crystallography (2006). Volume B, Reciprocal space. ISBN: 978-0-7923-6592-1, doi:10.1107/97809553602060000102.
Hermann-Mauguin entry aliases (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_entry_aliases
Alternative Hermann-Mauguin entry labels from International Tables for Crystallography Volume B table A1.4.2.7 that identify the same generated Hall-symbol row as hm_entry.
Hermann-Mauguin entry markups (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_entry_markup
Display-oriented renderings of the Hermann-Mauguin entry label in hm_entry.
Extended Hermann-Mauguin symbol (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_extended
The setting-specific extended Hermann-Mauguin symbol for the space-group setting.
Extended Hermann-Mauguin symbol aliases (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_extended_aliases
Alternate ASCII forms of hm_extended that are accepted for the same generated setting.
Extended Hermann-Mauguin alias markups (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_extended_aliases_markup
Display-oriented renderings corresponding element-by-element to the alternate extended Hermann-Mauguin symbols in hm_extended_aliases.
Extended Hermann-Mauguin symbol markups (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_extended_markup
Display-oriented renderings of the extended Hermann-Mauguin symbol in hm_extended.
Extended Hermann-Mauguin symbol in old notation (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_extended_old
The older extended Hermann-Mauguin symbol retained as an alias for symbols superseded by newer e-glide notation.
Full Hermann-Mauguin symbol (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_full
The setting-specific full Hermann-Mauguin symbol for the space-group setting.
Full Hermann-Mauguin symbol aliases (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_full_aliases
Alternate ASCII forms of hm_full that are accepted for the same generated setting.
Full Hermann-Mauguin alias markups (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_full_aliases_markup
Display-oriented renderings corresponding element-by-element to the alternate full Hermann-Mauguin symbols in hm_full_aliases.
Full Hermann-Mauguin symbol markups (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_full_markup
Display-oriented renderings of the setting-specific full Hermann-Mauguin symbol in hm_full.
Full Hermann-Mauguin symbol in old notation (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_full_old
The older full Hermann-Mauguin symbol retained as an alias for symbols superseded by newer e-glide notation.
Standard full Hermann-Mauguin symbol (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_full_std
The International Tables standard full Hermann-Mauguin symbol for the space-group type.
Standard full Hermann-Mauguin symbol markups (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_full_std_markup
Display-oriented renderings of the ITA-standard full Hermann-Mauguin symbol in hm_full_std.
Short Hermann-Mauguin symbol (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_short
The setting-specific short Hermann-Mauguin symbol for the space-group setting.
Short Hermann-Mauguin symbol aliases (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_short_aliases
Alternate ASCII forms of hm_short that are accepted for the same generated setting.
Short Hermann-Mauguin alias markups (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_short_aliases_markup
Display-oriented renderings corresponding element-by-element to the alternate short Hermann-Mauguin symbols in hm_short_aliases.
Short Hermann-Mauguin symbol markups (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_short_markup
Display-oriented renderings of the setting-specific short Hermann-Mauguin symbol in hm_short.
Short Hermann-Mauguin symbol in old notation (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_short_old
The older short Hermann-Mauguin symbol retained as an alias for symbols superseded by newer e-glide notation.
Standard short Hermann-Mauguin symbol (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_short_std
The International Tables standard short Hermann-Mauguin symbol for the space-group type.
Standard short Hermann-Mauguin symbol markups (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/hm_short_std_markup
Display-oriented renderings of the ITA-standard short Hermann-Mauguin symbol in hm_short_std.
is centric (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/is_centric
Whether the space group contains an inversion operation (W,w) with W = -I.
The inversion center need not be the coordinate origin; one such center is at w/2 in fractional coordinates.
This tests the space-group symmetry, not the centricity of an individual diffraction reflection.
is chiral (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/is_chiral
Whether every operation of the space group preserves handedness, i.e. every linear part has determinant +1.
This is cctbx's is_chiral() convention and identifies the 65 Sohncke space-group types, excluding mirrors, inversion, glide reflections, and rotoinversions.
It does not mean that the space-group type belongs to one of the 11 enantiomorphic pairs; that is recorded by is_enantiomorphic.
It does not by itself determine the handedness or chirality of a molecular motif.
is enantiomorphic (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/is_enantiomorphic
Boolean flag indicating whether the space-group type belongs to an enantiomorphic pair.
is reference setting (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/is_reference_setting
Whether cctbx identifies this Hall setting as its reference setting for the space-group type.
This is the reference used by cctbx's change-of-basis machinery; it must not be inferred solely from the setting-specific Hermann-Mauguin symbol.
For the pipeline's selected IT-standard setting, use index_it_number_to_std_spacegroups in the dataset's companion indicies structure.
International Tables coordinate-system code (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/it_coordinate_system_code
The International Tables coordinate-system code for the setting.
International Tables space-group number (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/it_number
The International Tables space-group number.
International Tables number of the enantiomorph (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/it_number_enantiomorphic
International Tables number of the enantiomorphic partner space group, when one exists.
Laue class (property) - https://schemas.httk.org/defs/v0.1/properties/pointgroups/laue_class
The Laue class associated with the space group or point group.
Number of centering translations (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/n_centering_translations
Number of centering translations in the conventional cell of the space-group setting.
Number of point-group operations (property) - https://schemas.httk.org/defs/v0.1/properties/pointgroups/n_pointgroup_symops
Number of point-group symmetry operations.
Number of symops (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/n_symops
Number of symmetry operations in the finite operation list of the generated entry.
Point-group Hermann-Mauguin symbol (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/point_group
The Hermann-Mauguin point-group symbol for the crystallographic point group of the space group.
Schoenflies symbol (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/schoenflies
The Schoenflies symbol for the space-group type.
Schoenflies symbol markups (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/schoenflies_markup
Display-oriented renderings of the space-group Schoenflies symbol in schoenflies.
The plain string value is stored in the corresponding unsuffixed property; this object only provides alternate markup forms for display.
Setting annotation (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/setting
Setting suffix or setting annotation extracted from the cctbx universal Hermann-Mauguin symbol in hm_cctbx_universal.
International Tables setting code n:c (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/setting_it_nc
International Tables setting identifier in n:c notation.
International Tables setting-code aliases (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/setting_it_nc_aliases
A list of International Tables n:c setting identifiers that are alternatives to the one designated as the main one.
Setting plaintext (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/setting_plaintext
Human-readable description of the International Tables coordinate-system setting.
Space-group symbols (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/spacegroup_symbols
Ordered table of conventional space-group symbol rows.
Spglib Hall symbol (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/spglib_hall
The Hall symbol for this setting as spelled by the spglib library.
Spglib Hall numbers (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/spglib_hall_numbers
The spglib Hall numbers corresponding to this Hall setting.
Structure seminvariants (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/structure_seminvariants
Structure-seminvariant vectors and moduli for the space-group setting, describing allowed changes of origin that preserve its symmetry description.
Symmetry operations (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/symops
Full list of symmetry-operation descriptors for a space-group setting.
Symmetry operation generators (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/symops_generators
Generator subset of the finite symmetry-operation list for a space-group setting.
Composition of these operations, with translations reduced modulo integer cell translations, generates symops, including the centering translations.
Integer cell translations are implicit generators of the infinite space group.
The generator selects operations greedily; the list is not promised to have the smallest possible cardinality.
Identity is omitted, so the P1 list is empty.
Symmetry operations modulo centering translations (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/symops_mod_centering
Representative symmetry-operation descriptors modulo centering translations.
Representative symmetry operations (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/symops_representative
Representative symmetry-operation descriptors modulo centering translations: one full-group operation (including inversion-related operations where present) per coset of the centring translations.
Wyckoff positions (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/wyckoff
Wyckoff-position table for a specific space-group setting.
Wyckoff sets (property) - https://schemas.httk.org/defs/v0.1/properties/spacegroups/wyckoff_sets
Sets of Wyckoff letters related by normalizer operations.
structure
Radial distribution function (property) - https://schemas.httk.org/defs/v0.1/properties/structure/radial_distribution_function
Radial distribution function g(r) of a structure or trajectory, binned in distance.
Steinhardt bond order (property) - https://schemas.httk.org/defs/v0.1/properties/structure/steinhardt_bond_order
Steinhardt bond-orientational order of a set of atoms, from spherical harmonics Y_lm of the directions of directed neighbour bonds within a cutoff. No neighbour-of-neighbour averaging and no crystalline/liquid classification is implied.
symmetry
Affine transformation (property) - https://schemas.httk.org/defs/v0.1/properties/symmetry/affine_transformation
An affine transformation acting on fractional crystallographic coordinates.
Basis transformation (property) - https://schemas.httk.org/defs/v0.1/properties/symmetry/basis_transform
One crystallographic transform between coordinate descriptions, settings, cells, or related group embeddings.
Centering translation (property) - https://schemas.httk.org/defs/v0.1/properties/symmetry/centering_translation
One centering translation of a conventional crystallographic cell.
Operation (property) - https://schemas.httk.org/defs/v0.1/properties/symmetry/op
Information related to a crystallographic operation acting within one coordinate setting.
Operation xyz (property) - https://schemas.httk.org/defs/v0.1/properties/symmetry/op_xyz
Coordinate operation expressed in the algebraic xyz form, also known as Jones' faithful representation (Bradley & Cracknell, 1972: pp. 35-37; adapted for computer strings).
Wyckoff position (property) - https://schemas.httk.org/defs/v0.1/properties/symmetry/wyckoff_position
Information related to a Wyckoff position in a space-group setting.
thermodynamics
Heat capacity at constant pressure (property) - https://schemas.httk.org/defs/v0.1/properties/thermodynamics/heat_capacity_constant_pressure
The heat capacity at constant pressure C_P, in electronvolt per kelvin (eV K^-1). Extensive quantity of the whole simulated cell. It may be obtained, e.g., from enthalpy fluctuations in the isothermal-isobaric ensemble as Var(H) / (kB T^2), at the temperature recorded alongside. A null value means the quantity is not available or not recorded.
Heat capacity at constant volume (property) - https://schemas.httk.org/defs/v0.1/properties/thermodynamics/heat_capacity_constant_volume
The heat capacity at constant volume C_V, in electronvolt per kelvin (eV K^-1). Extensive quantity of the whole simulated cell. It may be obtained, e.g., from canonical-ensemble energy fluctuations as Var(E) / (kB T^2), at the temperature recorded alongside. A null value means the quantity is not available or not recorded.
Helmholtz free energy (property) - https://schemas.httk.org/defs/v0.1/properties/thermodynamics/helmholtz_free_energy
The Helmholtz free energy F = U - T S, in electronvolt (eV), for the vibrational modes of the referenced cell, at the temperature recorded alongside. Extensive quantity of the whole simulated cell. For harmonic phonons F = sum over modes of [h nu / 2 + kB T ln(1 - exp(-h nu / (kB T)))]. The energy zero is the static (potential) energy of the referenced cell, which is not included. A null value means the quantity is not available or not recorded.
Isothermal compressibility (property) - https://schemas.httk.org/defs/v0.1/properties/thermodynamics/isothermal_compressibility
The isothermal compressibility kappa_T = -(1/V) (dV/dP)_T, in inverse gigapascal (GPa^-1; 1 GPa = 10^9 Pa). It is an intensive quantity of the referenced cell, at the temperature and pressure recorded alongside. A null value means the quantity is not available or not recorded.
Mode Grueneisen parameters (property) - https://schemas.httk.org/defs/v0.1/properties/thermodynamics/mode_gruneisen_parameters
Mode Grueneisen parameters from a local polynomial fit of the natural logarithm of caller-matched mode frequencies against the natural logarithm of the volume.
Phonon band structure (property) - https://schemas.httk.org/defs/v0.1/properties/thermodynamics/phonon_band_structure
Harmonic phonon frequencies of the referenced structure along a path of q-points through the Brillouin zone (a phonon dispersion).
Phonon density of states (property) - https://schemas.httk.org/defs/v0.1/properties/thermodynamics/phonon_density_of_states
Harmonic phonon density of states of the referenced structure as a function of frequency.
Quasiharmonic thermodynamics (property) - https://schemas.httk.org/defs/v0.1/properties/thermodynamics/quasiharmonic_thermodynamics
Quasiharmonic equilibrium properties as a function of temperature at zero pressure.
Vibrational entropy (property) - https://schemas.httk.org/defs/v0.1/properties/thermodynamics/vibrational_entropy
The vibrational entropy, in electronvolt per kelvin (eV K^-1), for the vibrational modes of the referenced cell, at the temperature recorded alongside. Extensive quantity of the whole simulated cell. A null value means the quantity is not available or not recorded.
Vibrational heat capacity (property) - https://schemas.httk.org/defs/v0.1/properties/thermodynamics/vibrational_heat_capacity
The harmonic constant-volume heat capacity, in electronvolt per kelvin (eV K^-1), for the vibrational modes of the referenced cell, at the temperature recorded alongside. Extensive quantity of the whole simulated cell. A null value means the quantity is not available or not recorded.
Vibrational internal energy (property) - https://schemas.httk.org/defs/v0.1/properties/thermodynamics/vibrational_internal_energy
The vibrational internal energy, in electronvolt (eV), for the vibrational modes of the referenced cell, at the temperature recorded alongside. Extensive quantity of the whole simulated cell. It includes the zero-point energy. A null value means the quantity is not available or not recorded.
Vibrational thermodynamics (property) - https://schemas.httk.org/defs/v0.1/properties/thermodynamics/vibrational_thermodynamics
Harmonic phonon thermodynamics of the vibrational modes of the referenced cell, tabulated as a function of temperature.
Volumetric thermal expansion (property) - https://schemas.httk.org/defs/v0.1/properties/thermodynamics/volumetric_thermal_expansion
The volumetric thermal expansion coefficient alpha_V = (1/V) (dV/dT)_P, in inverse kelvin (K^-1). It is the volumetric (not linear) coefficient, an intensive quantity of the referenced cell, at the pressure recorded alongside. A null value means the quantity is not available or not recorded.
Zero-point energy (property) - https://schemas.httk.org/defs/v0.1/properties/thermodynamics/zero_point_energy
The zero-point energy, sum over modes of h nu / 2, in electronvolt (eV), for the vibrational modes of the referenced cell. Extensive quantity of the whole simulated cell. Temperature independent. A null value means the quantity is not available or not recorded.
trajectories
Frame stresses (property) - https://schemas.httk.org/defs/v0.1/properties/trajectories/frame_stresses
The stress tensor of each frame of a trajectory, aligned with the trajectory frame axis (dim_frames).
Each tensor is given in Voigt order [xx, yy, zz, yz, xz, xy], with tensile stress positive, in gigapascal (GPa; 1 GPa = 10^9 Pa).
A null value indicates that the stress tensor of the corresponding frame is unknown.
Frame temperatures (property) - https://schemas.httk.org/defs/v0.1/properties/trajectories/frame_temperatures
The instantaneous temperature of each frame of a trajectory, in kelvin, aligned with the trajectory frame axis (dim_frames).
A null value indicates that the temperature of the corresponding frame is unknown.
Frame total energies (property) - https://schemas.httk.org/defs/v0.1/properties/trajectories/frame_total_energies
The total energy of each frame of a trajectory, in electronvolt, aligned with the trajectory frame axis (dim_frames).
A null value indicates that the energy of the corresponding frame is unknown.
The reference/zero of the total energy scale is method- and code-specific, so values are comparable only within one consistent computational setup.
Time step (property) - https://schemas.httk.org/defs/v0.1/properties/trajectories/time_step
The molecular-dynamics integration time step between consecutive frames, in femtosecond (fs; 1 fs = 10^-15 s).
A null value indicates that the time step is unknown.
transformations
Affine images (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/affine_images
Same-space-group affine images for a standard setting.
Affine normalizer (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/affine_normalizer
Affine normalizer coset representatives for one crystallographic space-group setting.
Affine normalizer coset data (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/affine_normalizer_coset_data
Ordered table of bounded affine normalizer coset-representative data for crystallographic space groups, with one item for each Hall setting.
Affine normalizer cosets (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/affine_normalizer_cosets
Runtime list of bounded affine normalizer coset representatives modulo the space group.
Backward lift criteria (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/backward_lift_criteria
Criteria table for one supergroup IT number used to lift occupied Wyckoff data from a subgroup back to that supergroup along a chosen Bärnighausen transform.
Bärnighausen subgroup transforms (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/baernighausen
Bärnighausen subgroup transform table for one parent setting or space-group type.
Continuous normalizer (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/continuous_normalizer
Parameterized continuous normalizer subspace for a setting.
Euclidean normalizer (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/euclidean_normalizer
Finite Euclidean normalizer operations for one crystallographic space-group setting.
Hall to IT standard transform (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/hall_to_it_std_transform
Exact basis and origin transform from one stored Hall setting to the International Tables standard Hall setting of the same space-group type.
Subgroup or transform index (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/index
Subgroup or transform index.
Isomorphic subgroup transforms (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/isomorphic_subgroups
Isomorphic subgroup transforms of bounded index for one parent setting or space-group type.
Klassengleiche subgroup subtype (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/k_subtype
Subtype of a klassengleiche (k) subgroup relation.
Maximal subgroup relations (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/maximal_subgroup_relations
Maximal non-isomorphic subgroup relations for International Tables space-group types.
Number of coset representatives (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/n_coset_representatives
Number of nontrivial coset representatives retained after deduplication modulo the space group.
Number of cosets (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/n_cosets
Number of affine normalizer coset representatives stored for the setting.
Number of linear parts (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/n_linear_parts
Number of distinct linear matrix parts represented in a normalizer or transform table.
Number of orthogonal cosets (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/n_orthogonal_cosets
Number of orthogonal affine normalizer coset representatives stored for the setting.
Number of raw candidates (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/n_raw_candidates
Number of accepted affine normalizer candidates generated before quotienting modulo the space group and before metric filtering. This is not the number of all linear matrices tested: candidates whose affine normalization equations have no solution are not counted.
Number of unique candidates (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/n_unique_candidates
Number of candidate affine operations remaining after exact duplicate removal.
Orthogonal affine normalizer (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/orthogonal_affine_normalizer
Orthogonal affine normalizer coset representatives for one crystallographic space-group setting.
Orthogonal affine normalizer cosets (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/orthogonal_affine_normalizer_cosets
Runtime list of orthogonal signed-permutation affine normalizer coset representatives modulo the space group.
Same-space-group affine images in the standard setting (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/same_space_group_affine_images_std
Same-space-group affine-image record for one International Tables standard setting.
Maximal subgroup type (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/subgroup_type
International Tables maximal subgroup class.
Criterion target (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/target
Exact right-hand side of a generated modular linear criterion, stored as a list of fraction strings.
To Hall entry (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/to_hall_entry
Target Hall-entry key to which a setting transform maps the current Hall setting.
Transformations per H-M entry (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/transformations_per_hm_entry
Transformation data grouped by H-M entry.
Transformations per IT number (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/transformations_per_it_number
Standard-setting transformation data grouped by International Tables space-group number.
Wyckoff splitting (property) - https://schemas.httk.org/defs/v0.1/properties/transformations/wyckoff_splitting
Wyckoff-position splitting data associated with a subgroup or same-space-group transform.
transport
Diffusion coefficient (property) - https://schemas.httk.org/defs/v0.1/properties/transport/diffusion_coefficient
The isotropic self-diffusion coefficient D = tr(D_ij) / 3, in square metre per second (m^2 s^-1). Obtained from Green-Kubo or Einstein relations. For example, from the slope of the mean-squared displacement divided by 2d (Einstein), or the time integral of the velocity autocorrelation function (Green-Kubo). The species or selection it refers to is recorded alongside. A null value means the quantity is not available or not recorded.
Diffusion prefactor (property) - https://schemas.httk.org/defs/v0.1/properties/transport/diffusion_prefactor
The diffusion prefactor D_0, in square metres per second, of an Arrhenius diffusion coefficient D = D_0 exp(-E_a / (k_B T)); E_a is the activation_energy.
A null value means the quantity is not available or not recorded.
Diffusion running integral (property) - https://schemas.httk.org/defs/v0.1/properties/transport/diffusion_running_integral
Running integral of the velocity autocorrelation tensor, as a function of upper integration limit.
Diffusion tensor (property) - https://schemas.httk.org/defs/v0.1/properties/transport/diffusion_tensor
The self-diffusion tensor D_ij, in square metre per second (m^2 s^-1), a 3x3 Cartesian tensor with both indices over dim_spatial in the Cartesian frame of the referenced cell.
Obtained from Green-Kubo or Einstein relations. The tensor is not assumed to be symmetric. The species or selection it refers to is recorded alongside.
A null value means the quantity is not available or not recorded.
Mean squared displacement (property) - https://schemas.httk.org/defs/v0.1/properties/transport/mean_squared_displacement
Mean squared displacement tensor as a function of lag time.
Shear viscosity (property) - https://schemas.httk.org/defs/v0.1/properties/transport/shear_viscosity
The shear viscosity, in pascal second (Pa s).
Obtained from Green-Kubo or Einstein relations. By the Green-Kubo relation eta = V / (kB T) times the time integral of
Shear viscosity running integral (property) - https://schemas.httk.org/defs/v0.1/properties/transport/shear_viscosity_running_integral
Green-Kubo running integral of the shear stress autocorrelation, as a function of upper integration limit.
Thermal conductivity (property) - https://schemas.httk.org/defs/v0.1/properties/transport/thermal_conductivity
The isotropic thermal conductivity, the mean of the diagonal of the thermal conductivity tensor, in watt per metre per kelvin (W m^-1 K^-1). Obtained from Green-Kubo or Einstein relations. A null value means the quantity is not available or not recorded.
Thermal conductivity running integral (property) - https://schemas.httk.org/defs/v0.1/properties/transport/thermal_conductivity_running_integral
Green-Kubo running integral of the heat-current autocorrelation, as a function of upper integration limit.
Thermal conductivity tensor (property) - https://schemas.httk.org/defs/v0.1/properties/transport/thermal_conductivity_tensor
The thermal conductivity tensor kappa_ij, in watt per metre per kelvin (W m^-1 K^-1), a 3x3 Cartesian tensor with both indices over dim_spatial in the Cartesian frame of the referenced cell.
Obtained from Green-Kubo or Einstein relations. By the Green-Kubo relation kappa_ij = 1 / (V kB T^2) times the time integral of
Velocity autocorrelation (property) - https://schemas.httk.org/defs/v0.1/properties/transport/velocity_autocorrelation
Velocity autocorrelation tensor as a function of lag time.
validation
Energy prediction errors (property) - https://schemas.httk.org/defs/v0.1/properties/validation/energy_prediction_errors
Per-atom total-energy prediction errors of a model against reference energies over a set of configurations.
Force prediction errors (property) - https://schemas.httk.org/defs/v0.1/properties/validation/force_prediction_errors
Force prediction errors of a model against reference forces over a set of configurations; atoms are matched in order between reference and prediction.
NVE energy drift (property) - https://schemas.httk.org/defs/v0.1/properties/validation/nve_energy_drift
Linear drift of the conserved total energy (kinetic plus potential) per atom along a selected interval of a trajectory in the NVE ensemble.
Stress prediction errors (property) - https://schemas.httk.org/defs/v0.1/properties/validation/stress_prediction_errors
Stress prediction errors of a model against reference stress tensors over a set of configurations.
standards
httk definition provider standard (standard) - https://schemas.httk.org/defs/v0.1/standards/httk
The httk definition provider standard, comprising the spacegroups, pointgroups, and transformations entry types for crystallographic symmetry data.
units
general
femtosecond (unit) - https://schemas.httk.org/defs/v0.1/units/si/general/femtosecond
A unit of time equal to 10^-15 seconds.
gigapascal (unit) - https://schemas.httk.org/defs/v0.1/units/si/general/gigapascal
A unit of pressure and stress equal to 10^9 pascals.
workflows
VASP general calculation ([unknown]) - https://schemas.httk.org/defs/v0.1/workflows/vasp-general
This workflow declaration defines the httk vasp-general workflow: it runs any VASP calculation whose input files the job supplies, all of them except the POTCAR, which may also be assembled from a pseudopotential library. It defines the meaning of its roles: input role initial_structure is a structures entry containing the structure the calculation starts from. Output role final_structure is a structures entry containing the structure the calculation ended with, and output role total_energy is a records entry containing the final total energy of the calculation.
VASP structure relaxation ([unknown]) - https://schemas.httk.org/defs/v0.1/workflows/vasp-relax
This workflow declaration defines the httk vasp-relax workflow: it relaxes the geometry of a crystal structure with VASP. It defines the meaning of its roles: input role initial_structure is a structures entry containing the structure to relax. Output role relaxed_structure is a structures entry containing the relaxed geometry, and output role total_energy is a records entry containing the final total energy of the relaxed structure.
VASP relaxation and static calculation ([unknown]) - https://schemas.httk.org/defs/v0.1/workflows/vasp-relax-static
This workflow declaration defines the httk vasp-relax-static workflow: it relaxes the geometry, then evaluates the relaxed structure with a final static calculation. It defines the meaning of its roles: input role initial_structure is a structures entry containing the structure to relax. Output role relaxed_structure is a structures entry containing the relaxed geometry, and output role total_energy is a records entry containing the total energy of the relaxed structure from the final static calculation.
VASP static calculation ([unknown]) - https://schemas.httk.org/defs/v0.1/workflows/vasp-static
This workflow declaration defines the httk vasp-static workflow: it performs a single-point total-energy evaluation of a fixed structure with VASP. It defines the meaning of its roles: input role initial_structure is a structures entry containing the structure to evaluate. Output role total_energy is a records entry containing the total energy of the structure.