httk property definitionsProperty definitions using the OPTIMADE property definition format, hosted by httk
This page documents an OPTIMADE Property Definition. See https://schemas.optimade.org/ for more information.
ID: https://schemas.httk.org/defs/v0.1/properties/thermodynamics/phonon_band_structure
Definition name: phonon_band_structure
Property name: Phonon band structure
Description: Harmonic phonon frequencies of the referenced structure along a path of q-points through the Brillouin zone (a phonon dispersion).
Type: dictionary
Implementation requirements:
- Support: OPTIONAL support in implementations, i.e., MAY be null.
Only dispersions along a path are meant.
Frequencies on a uniform q-point mesh belong in a phonon density of states, see phonon_density_of_states.
Requirements/Conventions:
It MUST be a dictionary with the following keys:
qpoints: REQUIRED; List of lists of 3 floats.
The q-points of the path, in path order, over the dimension _httk_dim_qpoints.
Each q-point is given in fractional coordinates (dimension dim_lattice) in the reciprocal basis of the referenced structure: the Cartesian wavevector is the sum of the coordinates times the reciprocal lattice vectors b_1, b_2, b_3, where b_i . a_j = 2 pi delta_ij for the lattice vectors a_j of the referenced structure.
The path is a sequence of straight segments.
A segment boundary inside the list is encoded by two consecutive labelled q-points: the same point listed twice with the same label (a junction) or two different points with different labels (a discontinuity, across which the frequencies are not continuous).
The first and last q-points of the list bound the first and last segment; they SHOULD be labelled.
Every segment MUST contain at least one q-point that is not a boundary point.
qpoint_label_indices: REQUIRED; List of integers.
The 0-based indices into qpoints of the q-points that carry a label, over the dimension _httk_dim_qpoint_labels.
Each index MUST be a valid index into qpoints, and the indices MUST be strictly increasing.
The list MAY be empty when the producer has no labels; the path is then a single continuous segment.
qpoint_labels: REQUIRED; List of strings.
The label of each q-point listed in qpoint_label_indices, over the dimension _httk_dim_qpoint_labels: qpoint_labels[i] labels the q-point qpoints[qpoint_label_indices[i]].
It MUST have the same length as qpoint_label_indices.
Labels are the names of high-symmetry points as given by the producer (for example GAMMA or \Gamma for the zone centre); no normalized vocabulary is implied.
frequencies: REQUIRED; List of lists of floats.
The phonon frequencies in THz (ordinary frequency nu, not angular frequency omega = 2 pi nu), as a list over the dimension _httk_dim_modes of lists over _httk_dim_qpoints: frequencies[m][q] is the frequency of mode m at the q-point qpoints[q].
The number of modes MUST equal 3 times the number of sites of the referenced structure.
Mode m at each q-point MUST be the (m+1)-th lowest frequency at that q-point: the modes are sorted at each q-point and are not reordered to follow branch crossings.
Producers converting data whose branches were reordered to follow eigenvector connectivity (for example phonopy's band connection) MUST sort the values at each q-point.
An imaginary frequency (a negative eigenvalue of the dynamical matrix) is given as the negative of its magnitude, following the phonopy convention.
The value refers to the referenced structure (the entry the record is a product of), which is the cell whose dynamical matrix was diagonalized; the q-point coordinates and the number of modes are only meaningful for that cell. A producer whose coordinates refer to a different cell MUST either reference that cell as the structure the value is a product of, or transform the coordinates to the referenced structure's reciprocal basis.
A null value means the quantity is not available or not recorded.
Examples:
JSON definition:
{
"$id": "https://schemas.httk.org/defs/v0.1/properties/thermodynamics/phonon_band_structure",
"$schema": "https://schemas.optimade.org/meta/v1.3/optimade/property_definition.json",
"title": "Phonon band structure",
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"x-optimade-definition": {
"kind": "property",
"version": "0.1.0",
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"label": "phonon_band_structure_thermodynamics_httk"
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"x-optimade-unit": "inapplicable",
"x-optimade-unit-definitions": [
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"title": "tera",
"symbol": "T",
"display-symbol": "T",
"description": "The tera SI prefix defined as a dimensionless multiple of 10\u00b9\u00b2, adopted into SI at its creation at the 11th CGPM Meeting in 1960, resolution 12.",
"resources": [
{
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"resource-id": "https://www.bipm.org/en/committees/cg/cgpm/11-1960/resolution-12"
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{
"relation": "Wikipedia article describing the SI prefixes",
"resource-id": "https://en.wikipedia.org/wiki/Metric_prefix"
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"defining-relation": {
"base-units": [],
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"scale": {
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"title": "hertz",
"symbol": "Hz",
"display-symbol": "Hz",
"description": "A unit for frequency equal to s\u207b\u00b9 using the current, or one of the historical, definitions of the SI units.\n\n\"The frequency of a periodic phenomenon is expressed in hertz, as the inverse of its period expressed in seconds.\" [9th CGPM meeting in 1946]\n\nThe hertz was defined at the 9th CGPM Meeting in 1946, included in SI at the 11th CGPM meeting in 1960, resolution 12 and implicitly redefined via the redefinition of the second at the 13th CGPM Meeting in 1967, resolution 1.\n\nThis is a generalized definition taken to reference the current, or one of the historical, SI unit definitions.\nThis definition is intended for situations when it is not possible to be more precise, e.g., in contexts where data have been collected that uses different historical SI definitions.",
"compatibility": [
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"resources": [
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"relation": "Definition at the 9th CGPM meeting (1948)",
"resource-id": "https://www.bipm.org/en/committees/cg/cgpm/9-1948"
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{
"relation": "Definition and establishment of the SI unit system at the 11th CGPM meeting (1960), resolution 12.",
"resource-id": "https://www.bipm.org/en/committees/cg/cgpm/11-1960/resolution-12"
},
{
"relation": "Redefinition of the second in the 13th CGPM Meeting (1967), resolution 1",
"resource-id": "https://www.bipm.org/en/committees/cg/cgpm/13-1967/resolution-1"
},
{
"relation": "Wikipedia article describing the unit",
"resource-id": "https://en.wikipedia.org/wiki/Hertz"
}
],
"defining-relation": {
"base-units": [
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"id": "https://schemas.optimade.org/defs/v1.2/units/si/general/second"
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"base-units-expression": "s^-1"
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],
"x-optimade-requirements": {
"support": "may",
"sortable": false,
"query-support": "none"
},
"type": [
"object",
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"required": [
"qpoints",
"qpoint_label_indices",
"qpoint_labels",
"frequencies"
],
"description": "Harmonic phonon frequencies of the referenced structure along a path of q-points through the Brillouin zone (a phonon dispersion).\n\nOnly dispersions along a path are meant.\nFrequencies on a uniform q-point mesh belong in a phonon density of states, see `phonon_density_of_states`.\n\n**Requirements/Conventions**:\n\n- It MUST be a dictionary with the following keys:\n\n - **qpoints**: REQUIRED; List of lists of 3 floats.\n The q-points of the path, in path order, over the dimension `_httk_dim_qpoints`.\n Each q-point is given in fractional coordinates (dimension `dim_lattice`) in the reciprocal basis of the referenced structure: the Cartesian wavevector is the sum of the coordinates times the reciprocal lattice vectors b_1, b_2, b_3, where b_i . a_j = 2 pi delta_ij for the lattice vectors a_j of the referenced structure.\n The path is a sequence of straight segments.\n A segment boundary inside the list is encoded by two consecutive labelled q-points: the same point listed twice with the same label (a junction) or two different points with different labels (a discontinuity, across which the frequencies are not continuous).\n The first and last q-points of the list bound the first and last segment; they SHOULD be labelled.\n Every segment MUST contain at least one q-point that is not a boundary point.\n\n - **qpoint\\_label\\_indices**: REQUIRED; List of integers.\n The 0-based indices into `qpoints` of the q-points that carry a label, over the dimension `_httk_dim_qpoint_labels`.\n Each index MUST be a valid index into `qpoints`, and the indices MUST be strictly increasing.\n The list MAY be empty when the producer has no labels; the path is then a single continuous segment.\n\n - **qpoint\\_labels**: REQUIRED; List of strings.\n The label of each q-point listed in `qpoint_label_indices`, over the dimension `_httk_dim_qpoint_labels`: `qpoint_labels[i]` labels the q-point `qpoints[qpoint_label_indices[i]]`.\n It MUST have the same length as `qpoint_label_indices`.\n Labels are the names of high-symmetry points as given by the producer (for example `GAMMA` or `\\Gamma` for the zone centre); no normalized vocabulary is implied.\n\n - **frequencies**: REQUIRED; List of lists of floats.\n The phonon frequencies in THz (ordinary frequency nu, not angular frequency omega = 2 pi nu), as a list over the dimension `_httk_dim_modes` of lists over `_httk_dim_qpoints`: `frequencies[m][q]` is the frequency of mode m at the q-point `qpoints[q]`.\n The number of modes MUST equal 3 times the number of sites of the referenced structure.\n Mode m at each q-point MUST be the (m+1)-th lowest frequency at that q-point: the modes are sorted at each q-point and are not reordered to follow branch crossings.\n Producers converting data whose branches were reordered to follow eigenvector connectivity (for example phonopy's band connection) MUST sort the values at each q-point.\n An imaginary frequency (a negative eigenvalue of the dynamical matrix) is given as the negative of its magnitude, following the phonopy convention.\n\n- The value refers to the referenced structure (the entry the record is a product of), which is the cell whose dynamical matrix was diagonalized; the q-point coordinates and the number of modes are only meaningful for that cell.\n A producer whose coordinates refer to a different cell MUST either reference that cell as the structure the value is a product of, or transform the coordinates to the referenced structure's reciprocal basis.\n\nA null value means the quantity is not available or not recorded.",
"properties": {
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"x-optimade-unit": "inapplicable",
"x-optimade-dimensions": {
"names": [
"_httk_dim_qpoints"
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"sizes": [
null
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"type": [
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"description": "The q-points of the path in fractional coordinates of the reciprocal basis of the referenced structure, in path order.",
"items": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
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"qpoint_label_indices": {
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"x-optimade-unit": "inapplicable",
"x-optimade-dimensions": {
"names": [
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"sizes": [
null
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"type": [
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"description": "The strictly increasing 0-based indices into `qpoints` of the labelled q-points.",
"items": {
"x-optimade-type": "integer",
"x-optimade-unit": "dimensionless",
"type": [
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}
},
"qpoint_labels": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"x-optimade-dimensions": {
"names": [
"_httk_dim_qpoint_labels"
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"sizes": [
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"type": [
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"description": "The label of each q-point listed in `qpoint_label_indices`, in the same order.",
"items": {
"x-optimade-type": "string",
"x-optimade-unit": "inapplicable",
"type": [
"string"
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}
},
"frequencies": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"x-optimade-dimensions": {
"names": [
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],
"sizes": [
null
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},
"type": [
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"description": "The phonon frequencies per mode and q-point, with imaginary frequencies given as negative values.",
"items": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"x-optimade-dimensions": {
"names": [
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"type": [
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"items": {
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"x-optimade-unit": "THz",
"type": [
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}
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}
}
}