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/transformations/orthogonal_affine_normalizer
Definition name: orthogonal_affine_normalizer
Property name: Orthogonal affine normalizer
Description: Orthogonal affine normalizer coset representatives for one crystallographic space-group setting.
Type: dictionary
The representatives are listed modulo the space group itself, so each listed operation represents an equivalence class of affine normalizer operations rather than every operation in that class. This property contains the signed-permutation subset of affine normalizer representatives.
The candidate_set field belongs in this property because the listed representatives are produced from a deliberately restricted finite candidate set.
For this property candidate_set is signed_permutation_matrices, meaning 3 by 3 integer matrices with exactly one nonzero entry in each row and column and each nonzero entry equal to -1 or 1.
The plural field candidate_sets is not part of the emitted data and MUST NOT be used here.
This property is one of three related normalizer tables for a setting:
euclidean_normalizer holds the finite Euclidean normalizer operations obtained from cctbx,
this property holds the older bounded table restricted to signed-permutation linear parts,
and affine_normalizer holds the bounded table generated from unimodular integer linear parts, whose linear candidate set contains the signed-permutation set.
Requirements/Conventions:
It MUST be a dictionary with the following keys:
normalizer_kind: REQUIRED; String. Kind label for this normalizer contribution.
representation: REQUIRED; String. Representation label for the listed data.
candidate_set: REQUIRED; String. Name of the finite linear candidate set used for generation.
n_symops: REQUIRED; Integer.
Number of listed coset representatives after metric-compatibility filtering.
It MUST equal the length of symops.
n_linear_parts: REQUIRED; Integer.
Number of distinct exact linear matrix parts represented in symops.
This count ignores translation differences and can be smaller than n_symops.
n_raw_candidates: REQUIRED; Integer. Number of accepted affine normalizer candidates generated before quotienting by the space group and metric filtering; the candidate list itself is not stored.
n_unique_candidates: OPTIONAL; Integer. Legacy count of unique affine candidates before quotienting by the space group. The current canonical-coset composition does not emit this field; it is retained to describe older records.
n_coset_representatives: REQUIRED; Integer. Number of non-trivial coset representatives before metric-compatibility filtering.
bounds: REQUIRED; Dictionary. Simple numerical bounds satisfied by the signed-permutation candidate matrices.
symops: REQUIRED; List of dictionaries.
Listed orthogonal affine normalizer coset representatives.
Each item follows /defs/v0.1/properties/symmetry/basis_transform.
Each item MUST carry compatible_systems, the list of reference-setting metric families whose every metric tensor is preserved after transport to the actual setting basis.
For the infinite space group G, an affine map A normalizes G when A*G*A^-1 = G, including its full translation lattice.
Representatives differing by multiplication by an element of G describe the same coset.
The identity coset G itself is omitted, but a nonzero pure translation can represent a nontrivial coset and MUST NOT be discarded just because its matrix is identity.
Continuous origin shifts are represented separately by continuous_normalizer; this finite list is not all of N_A(G)/G.
A nonempty compatible_systems list means the linear part preserves every metric in at least one listed reference-setting family after transport to the recorded Hall basis.
It need not preserve the actual setting's general metric; that distinction is recorded by affine_transformation.is_orthogonal.
The signed-permutation candidate set is contained in the bounded integer candidate set, but independently chosen coset representatives need not appear as identical affine matrices and vectors in both lists.
The historical word orthogonal names the signed-permutation search: M^T*M = I as a numerical matrix condition.
In a fractional basis this is not sufficient for physical orthogonality, which instead requires M^T*g*M = g for the relevant lattice metric g.
The example is the nontrivial half-cell origin-shift coset for Pm-3m (No. 221); multiplication by inversion in the space group explains the displayed linear part -I.
Examples:
{"normalizer_kind": "orthogonal_affine", "representation": "orthogonal_coset_representatives", "candidate_set": "signed_permutation_matrices", "n_symops": 1, "n_linear_parts": 1, "n_raw_candidates": 96, "n_coset_representatives": 1, "bounds": {"det_abs": 1, "max_abs_linear_entry": 1}, "symops": [{"compatible_systems": ["triclinic", "monoclinic", "orthorhombic", "tetragonal", "trigonal", "hexagonal", "cubic"], "affine_transformation": {"matrix": [["-1", "0", "0"], ["0", "-1", "0"], ["0", "0", "-1"]], "vector": ["1/2", "1/2", "1/2"], "xyz": "-x+1/2,-y+1/2,-z+1/2", "det": -1, "is_orthogonal": true}, "operation_kind": "orthogonal_affine"}]}JSON definition:
{
"$id": "https://schemas.httk.org/defs/v0.1/properties/transformations/orthogonal_affine_normalizer",
"$schema": "https://schemas.optimade.org/meta/v1.3/optimade/property_definition.json",
"title": "Orthogonal affine normalizer",
"x-optimade-type": "dictionary",
"x-optimade-definition": {
"kind": "property",
"version": "0.1.0",
"format": "1.3",
"name": "orthogonal_affine_normalizer",
"label": "orthogonal_affine_normalizer_transformations"
},
"x-optimade-unit": "inapplicable",
"type": [
"object",
"null"
],
"description": "Orthogonal affine normalizer coset representatives for one crystallographic space-group setting.\n\nThe representatives are listed modulo the space group itself, so each listed operation represents an equivalence class of affine normalizer operations rather than every operation in that class.\nThis property contains the signed-permutation subset of affine normalizer representatives.\n\nThe `candidate_set` field belongs in this property because the listed representatives are produced from a deliberately restricted finite candidate set.\nFor this property `candidate_set` is `signed_permutation_matrices`, meaning 3 by 3 integer matrices with exactly one nonzero entry in each row and column and each nonzero entry equal to `-1` or `1`.\nThe plural field `candidate_sets` is not part of the emitted data and MUST NOT be used here.\n\nThis property is one of three related normalizer tables for a setting:\n`euclidean_normalizer` holds the finite Euclidean normalizer operations obtained from cctbx,\nthis property holds the older bounded table restricted to signed-permutation linear parts,\nand `affine_normalizer` holds the bounded table generated from unimodular integer linear parts, whose linear candidate set contains the signed-permutation set.\n\n**Requirements/Conventions**:\n\n- It MUST be a dictionary with the following keys:\n\n - **normalizer\\_kind**: REQUIRED; String.\n Kind label for this normalizer contribution.\n\n - **representation**: REQUIRED; String.\n Representation label for the listed data.\n\n - **candidate\\_set**: REQUIRED; String.\n Name of the finite linear candidate set used for generation.\n\n - **n\\_symops**: REQUIRED; Integer.\n Number of listed coset representatives after metric-compatibility filtering.\n It MUST equal the length of `symops`.\n\n - **n\\_linear\\_parts**: REQUIRED; Integer.\n Number of distinct exact linear matrix parts represented in `symops`.\n This count ignores translation differences and can be smaller than `n_symops`.\n\n - **n\\_raw\\_candidates**: REQUIRED; Integer.\n Number of accepted affine normalizer candidates generated before quotienting by the space group and metric filtering; the candidate list itself is not stored.\n\n - **n\\_unique\\_candidates**: OPTIONAL; Integer.\n Legacy count of unique affine candidates before quotienting by the space group.\n The current canonical-coset composition does not emit this field; it is retained to describe older records.\n\n - **n\\_coset\\_representatives**: REQUIRED; Integer.\n Number of non-trivial coset representatives before metric-compatibility filtering.\n\n - **bounds**: REQUIRED; Dictionary.\n Simple numerical bounds satisfied by the signed-permutation candidate matrices.\n\n - **symops**: REQUIRED; List of dictionaries.\n Listed orthogonal affine normalizer coset representatives.\n Each item follows `/defs/v0.1/properties/symmetry/basis_transform`.\n Each item MUST carry `compatible_systems`, the list of reference-setting metric families whose every metric tensor is preserved after transport to the actual setting basis.\n\nFor the infinite space group G, an affine map A normalizes G when `A*G*A^-1 = G`, including its full translation lattice.\nRepresentatives differing by multiplication by an element of G describe the same coset.\nThe identity coset G itself is omitted, but a nonzero pure translation can represent a nontrivial coset and MUST NOT be discarded just because its matrix is identity.\nContinuous origin shifts are represented separately by `continuous_normalizer`; this finite list is not all of `N_A(G)/G`.\nA nonempty `compatible_systems` list means the linear part preserves every metric in at least one listed reference-setting family after transport to the recorded Hall basis.\nIt need not preserve the actual setting's general metric; that distinction is recorded by `affine_transformation.is_orthogonal`.\nThe signed-permutation candidate set is contained in the bounded integer candidate set, but independently chosen coset representatives need not appear as identical affine matrices and vectors in both lists.\n\nThe historical word orthogonal names the signed-permutation search: `M^T*M = I` as a numerical matrix condition.\nIn a fractional basis this is not sufficient for physical orthogonality, which instead requires `M^T*g*M = g` for the relevant lattice metric g.\n\nThe example is the nontrivial half-cell origin-shift coset for Pm-3m (No. 221); multiplication by inversion in the space group explains the displayed linear part `-I`.",
"properties": {
"normalizer_kind": {
"x-optimade-type": "string",
"x-optimade-unit": "inapplicable",
"type": [
"string",
"null"
],
"description": "Kind label for this normalizer contribution.",
"enum": [
"orthogonal_affine",
null
]
},
"representation": {
"x-optimade-type": "string",
"x-optimade-unit": "inapplicable",
"type": [
"string",
"null"
],
"description": "Representation label for the listed normalizer data.",
"enum": [
"orthogonal_coset_representatives",
null
]
},
"candidate_set": {
"x-optimade-type": "string",
"x-optimade-unit": "inapplicable",
"type": [
"string",
"null"
],
"description": "Name of the finite linear candidate set used for generation.",
"enum": [
"signed_permutation_matrices",
null
]
},
"n_symops": {
"$id": "https://schemas.httk.org/defs/v0.1/properties/spacegroups/n_symops",
"title": "Number of symops",
"x-optimade-type": "integer",
"x-optimade-definition": {
"kind": "property",
"version": "0.1.0",
"format": "1.3",
"name": "n_symops",
"label": "n_symops_spacegroups"
},
"type": [
"integer",
"null"
],
"description": "Number of symmetry operations in the finite operation list of the generated entry.\n\nWhen the entry contains a `symops` list, this value MUST equal its length.",
"x-optimade-unit": "inapplicable",
"examples": [
1,
2
]
},
"n_linear_parts": {
"$id": "https://schemas.httk.org/defs/v0.1/properties/transformations/n_linear_parts",
"title": "Number of linear parts",
"x-optimade-type": "integer",
"x-optimade-definition": {
"kind": "property",
"version": "0.1.0",
"format": "1.3",
"name": "n_linear_parts",
"label": "n_linear_parts_transformations"
},
"type": [
"integer",
"null"
],
"description": "Number of distinct linear matrix parts represented in a normalizer or transform table.\n\nDistinctness is determined by exact element-wise comparison of the 3 by 3 matrix parts of the listed operations.\n\nThis value MUST equal the number of distinct `affine_transformation.matrix` values in the containing `symops` list when that list is present; translation differences do not increase it.",
"x-optimade-unit": "inapplicable",
"examples": [
2,
4
]
},
"n_raw_candidates": {
"x-optimade-type": "integer",
"x-optimade-unit": "inapplicable",
"type": [
"integer",
"null"
],
"description": "Number of accepted affine normalizer candidates generated before quotienting by the space group and metric filtering; the candidate list itself is not stored."
},
"n_unique_candidates": {
"x-optimade-type": "integer",
"x-optimade-unit": "inapplicable",
"type": [
"integer",
"null"
],
"description": "Legacy count of unique affine candidates before quotienting by the space group; omitted by the current generator."
},
"n_coset_representatives": {
"x-optimade-type": "integer",
"x-optimade-unit": "inapplicable",
"type": [
"integer",
"null"
],
"description": "Number of non-trivial coset representatives before metric-compatibility filtering."
},
"bounds": {
"x-optimade-type": "dictionary",
"x-optimade-unit": "inapplicable",
"type": [
"object",
"null"
],
"description": "Simple numerical bounds satisfied by the signed-permutation candidate matrices.",
"properties": {
"det_abs": {
"x-optimade-type": "integer",
"x-optimade-unit": "inapplicable",
"type": [
"integer",
"null"
],
"description": "Absolute determinant of every signed-permutation candidate matrix."
},
"max_abs_linear_entry": {
"x-optimade-type": "integer",
"x-optimade-unit": "inapplicable",
"type": [
"integer",
"null"
],
"description": "Maximum absolute entry value in the signed-permutation candidate matrices."
}
}
},
"symops": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"type": [
"array",
"null"
],
"description": "Listed orthogonal affine normalizer coset representatives.",
"items": {
"$id": "https://schemas.httk.org/defs/v0.1/properties/symmetry/basis_transform",
"title": "Basis transformation",
"x-optimade-type": "dictionary",
"x-optimade-definition": {
"kind": "property",
"version": "0.1.0",
"format": "1.3",
"name": "basis_transform",
"label": "basis_transform_symmetry"
},
"x-optimade-unit": "inapplicable",
"type": [
"object",
"null"
],
"description": "One crystallographic transform between coordinate descriptions, settings, cells, or related group embeddings.\n\nThe affine map itself is stored in the embedded `affine_transformation` field.\nThe parent property defines the source and target coordinate systems and the precise role of the transform.\nFor a subgroup embedding the convention is `x_G = P*x_H + p`, where `P = affine_transformation.matrix` and `p = affine_transformation.vector`.\nThe columns of `P` are the subgroup cell vectors expressed in the parent fractional basis, and `p` is the subgroup origin expressed in that basis.\nThus conversion of parent coordinates to subgroup coordinates uses `x_H = P^-1*(x_G-p)`, not the forward affine map.\nUseful, for example, for representing setting changes, subgroup embeddings, isomorphic subgroup transforms, normalizer representatives, and same-space-group affine images.\nThis property is not limited to symmetry operations within one fixed setting; the matrix may be non-orthogonal or have determinant different from one when the transform changes cell or basis.\n\n**Requirements/Conventions**:\n\n- It MUST be a dictionary with the following keys:\n\n - **affine\\_transformation**: REQUIRED; Dictionary.\n Exact affine map for the transform, using exact rational matrix and vector entries.\n The coordinate convention and source/target interpretation are supplied by the parent property.\n\n - **index**: OPTIONAL; Integer or null.\n Index metadata whose interpretation is defined by the parent property.\n Common uses include the subgroup index for subgroup embeddings, the cell index for isomorphic subgroup transforms, or an ordinal representative index in a finite transform table.\n\n - **subgroup\\_type**: OPTIONAL; String.\n Translation/point-symmetry classification when supplied for a subgroup embedding.\n The value MUST be `t` for a translationengleiche subgroup or `k` for a klassengleiche subgroup.\n It MUST be omitted for identity embeddings and general subgroups that lose both translations and point symmetry, and for transforms that are not subgroup embeddings.\n Presence of `t` or `k` alone does not certify maximality; the containing relation table supplies that information.\n\n - **k\\_subtype**: OPTIONAL; String or null.\n Klassengleiche subtype when the transform describes a klassengleiche subgroup relation.\n The value MUST be `loss_of_centering_translation` or `enlarged_unit_cell` for klassengleiche relations and null or omitted otherwise.\n\n - **compatible\\_systems**: OPTIONAL; List of strings.\n Reference-setting metric families whose every metric tensor is preserved by the linear part after transport to the actual setting basis.\n This is used for bounded affine normalizer representatives.\n\n - **operation\\_kind**: OPTIONAL; String.\n Categorical label for normalizer-type representatives.\n The value MUST be `euclidean` for Euclidean normalizer operations, `orthogonal_affine` for the signed-permutation affine normalizer subset, or `affine` for the bounded unimodular affine normalizer table.\n It MUST be omitted when the transform is a setting transform, subgroup embedding, or other transform for which no normalizer operation class applies.\n\n - **wyckoff\\_splitting**: OPTIONAL; List.\n Wyckoff-position splitting metadata induced by the transform when available.\n The list is grouped by explicit parent Wyckoff letter.\n\n - **criteria**: OPTIONAL; List.\n Backward-lift constraint metadata induced by the transform when available.\n The list is grouped by explicit parent Wyckoff letter.",
"properties": {
"affine_transformation": {
"$id": "https://schemas.httk.org/defs/v0.1/properties/symmetry/affine_transformation",
"title": "Affine transformation",
"x-optimade-type": "dictionary",
"x-optimade-definition": {
"kind": "property",
"version": "0.1.0",
"format": "1.3",
"name": "affine_transformation",
"label": "affine_transformation_symmetry"
},
"x-optimade-unit": "inapplicable",
"type": [
"object",
"null"
],
"description": "An affine transformation acting on fractional crystallographic coordinates.\n\nAn invertible affine transformation preserves collinearity and parallelism, but need not preserve Euclidean distances or angles.\nA singular affine map can collapse a line or plane to a lower-dimensional image.\nThe transformation is represented by a 3 by 3 matrix and a 3-vector, both serialized with exact string entries.\nWith column vectors, the map is `u_out = matrix * u_in + vector`; matrix rows specify the three output components.\nThe containing property identifies whether `u_in` denotes fractional coordinates or abstract Wyckoff parameters and identifies the input and output settings.\nNo wrapping modulo lattice translations is implicit in this equation; apply any required periodic reduction only in the specified output setting.\nThe transformation may, for example, represent an operation within one setting, a setting transform, a subgroup embedding, a normalizer representative, or a parametric coordinate map for a Wyckoff-position orbit representative.\nWhen used as a parametric coordinate map, the matrix may be singular because special Wyckoff positions can constrain or identify parameters.\n\n**Requirements/Conventions**:\n\n- It MUST be a dictionary with the following keys:\n\n - **matrix**: REQUIRED; Exact 3x3 matrix.\n Matrix part of the affine transformation.\n It MUST be represented as a list of three row lists, each containing three exact rational entries represented as strings.\n\n - **vector**: REQUIRED; List of 3 Fractions (String).\n Translation or origin-shift vector of the affine transformation in fractional coordinates.\n\n - **xyz**: OPTIONAL; String.\n Coordinate expression for the affine transformation in `x,y,z` notation when available.\n It MUST express the same affine map as `matrix` and `vector`, using `x,y,z` for the input components.\n\n - **det**: OPTIONAL; Integer.\n Determinant of `matrix` when the generator emits it.\n\n - **is\\_orthogonal**: OPTIONAL; Boolean.\n Whether the linear part preserves the crystallographic metric family specified by the containing setting; this is not a test of the fractional matrix against the Cartesian identity metric.",
"properties": {
"matrix": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"x-optimade-dimensions": {
"names": [
"dim_lattice",
"dim_lattice"
],
"sizes": [
3,
3
]
},
"type": [
"array",
"null"
],
"description": "Exact 3 by 3 matrix part of the affine transformation.",
"items": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"x-optimade-dimensions": {
"names": [
"dim_lattice"
],
"sizes": [
3
]
},
"type": [
"array"
],
"description": "One row of the exact 3 by 3 matrix.",
"items": {
"$id": "https://schemas.httk.org/defs/v0.1/properties/core/fraction",
"title": "Fraction",
"x-optimade-type": "string",
"x-optimade-definition": {
"label": "fraction_core",
"kind": "property",
"version": "0.1.0",
"format": "1.3",
"name": "fraction"
},
"type": [
"string",
"null"
],
"description": "A numerical representation formed as the quotient of two numbers represented as a string.",
"examples": [
"2/3",
"5/42",
"10",
"0"
],
"x-optimade-unit": "inapplicable"
}
}
},
"vector": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"x-optimade-dimensions": {
"names": [
"dim_lattice"
],
"sizes": [
3
]
},
"type": [
"array",
"null"
],
"description": "Exact fractional-coordinate vector part of the affine transformation.",
"items": {
"$id": "https://schemas.httk.org/defs/v0.1/properties/core/fraction",
"title": "Fraction",
"x-optimade-type": "string",
"x-optimade-definition": {
"label": "fraction_core",
"kind": "property",
"version": "0.1.0",
"format": "1.3",
"name": "fraction"
},
"type": [
"string",
"null"
],
"description": "A numerical representation formed as the quotient of two numbers represented as a string.",
"examples": [
"2/3",
"5/42",
"10",
"0"
],
"x-optimade-unit": "inapplicable"
}
},
"xyz": {
"$id": "https://schemas.httk.org/defs/v0.1/properties/symmetry/op_xyz",
"title": "Operation xyz",
"x-optimade-type": "string",
"x-compatibility": [
"https://schemas.optimade.org/defs/v1.2/properties/optimade/common/symmetry_operation_xyz",
"https://www.iucr.org/__data/iucr/cifdic_html/2/cif_sym.dic/Ispace_group_symop.operation_xyz.html"
],
"x-optimade-definition": {
"kind": "property",
"version": "0.1.0",
"format": "1.3",
"name": "op_xyz",
"label": "op_xyz_symmetry"
},
"x-optimade-unit": "inapplicable",
"type": [
"string",
"null"
],
"description": "Coordinate operation expressed in the algebraic xyz form, also known as Jones' faithful representation (Bradley & Cracknell, 1972: pp. 35-37; adapted for computer strings).\n\nThe following definition is adapted from (and meant to be compatible with) the IUCr symCIF version 1.0.1 dictionary definition of `_space_group_symop.operation_xyz` referenced to: International Tables for Crystallography (2002). Volume A, Space-group symmetry, edited by Th. Hahn, 5th. ed. (Kluwer Academic Publishers).\nIt is available at: https://www.iucr.org/__data/iucr/cifdic_html/2/cif_sym.dic/Ispace_group_symop.operation_xyz.html\n\nIf W is a matrix representation of the rotational part of the symmetry operation defined by the positions and signs of x, y and z, and w is a column of translations defined by the fractions, an equivalent position X' is generated from a given position X by the equation: X' = WX + w.",
"x-undef-pattern": "^([-+]?[xyz]([-+][xyz])?([-+](1/2|[12]/3|[1-3]/4|[1-5]/6))?|[-+]?(1/2|[12]/3|[1-3]/4|[1-5]/6)([-+][xyz]([-+][xyz])?)?),([-+]?[xyz]([-+][xyz])?([-+](1/2|[12]/3|[1-3]/4|[1-5]/6))?|[-+]?(1/2|[12]/3|[1-3]/4|[1-5]/6)([-+][xyz]([-+][xyz])?)?),([-+]?[xyz]([-+][xyz])?([-+](1/2|[12]/3|[1-3]/4|[1-5]/6))?|[-+]?(1/2|[12]/3|[1-3]/4|[1-5]/6)([-+][xyz]([-+][xyz])?)?)$",
"examples": [
"-x,-y,z",
"x,1/2-y,1/2+z"
]
},
"det": {
"x-optimade-type": "integer",
"x-optimade-unit": "inapplicable",
"type": [
"integer",
"null"
],
"description": "Determinant of the matrix part when emitted by the generator.\nThis optional integer annotation MUST equal the exact determinant of `matrix`; its absence does not imply determinant one.\nRational matrices can have noninteger determinants, in which case this integer annotation is omitted."
},
"is_orthogonal": {
"x-optimade-type": "boolean",
"x-optimade-unit": "inapplicable",
"type": [
"boolean",
"null"
],
"description": "Whether the matrix part is an isometry of the setting's metric, i.e. it preserves every metric tensor of the setting's crystal family expressed in this basis.\nFor a same-setting matrix `M` and metric tensor `g`, the criterion is `M^T g M = g` for every positive-definite metric in that family.\nThis is orthogonality with respect to the actual (generally non-Cartesian) lattice metric, not orthogonality of the matrix as a plain array: hexagonal sixfold rotations are isometries, whereas a cell-enlarging transform is not."
}
},
"examples": [
{
"matrix": [
[
"-1",
"0",
"0"
],
[
"0",
"-1",
"0"
],
[
"0",
"0",
"1"
]
],
"vector": [
"0",
"0",
"0"
],
"xyz": "-x,-y,z",
"det": 1,
"is_orthogonal": true
}
]
},
"index": {
"x-optimade-type": "integer",
"x-optimade-unit": "inapplicable",
"type": [
"integer",
"null"
],
"description": "Index metadata whose interpretation is supplied by the parent property."
},
"subgroup_type": {
"x-optimade-type": "string",
"x-optimade-unit": "inapplicable",
"type": [
"string"
],
"description": "International Tables subgroup-type label when applicable.",
"enum": [
"t",
"k"
]
},
"k_subtype": {
"x-optimade-type": "string",
"x-optimade-unit": "inapplicable",
"type": [
"string",
"null"
],
"description": "Klassengleiche subtype when applicable; follows the cell-dependent convention defined in `/defs/v0.1/properties/transformations/k_subtype`.",
"enum": [
"loss_of_centering_translation",
"enlarged_unit_cell",
null
]
},
"compatible_systems": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"type": [
"array",
"null"
],
"description": "Crystal metric families, named by reference-setting crystal system, whose metric tensors are all preserved by the transform.\nEach family is the full linear space of metric tensors of that crystal system in the reference setting (including unconstrained cross terms), transported to the basis of the actual setting.\nMonoclinic reference metrics use unique axis b; trigonal and hexagonal reference metrics both use hexagonal axes with a = b and gamma = 120 degrees.\nThese labels describe the tested metric families, not a reassignment of the space group's crystal system or the accidental metric symmetry of a particular specimen.",
"items": {
"x-optimade-type": "string",
"x-optimade-unit": "inapplicable",
"type": [
"string"
],
"description": "One compatible crystal-system label.",
"enum": [
"triclinic",
"monoclinic",
"orthorhombic",
"tetragonal",
"trigonal",
"hexagonal",
"cubic"
]
}
},
"operation_kind": {
"x-optimade-type": "string",
"x-optimade-unit": "inapplicable",
"type": [
"string"
],
"description": "Categorical label for normalizer-type representatives.",
"enum": [
"euclidean",
"orthogonal_affine",
"affine"
]
},
"wyckoff_splitting": {
"$id": "https://schemas.httk.org/defs/v0.1/properties/transformations/wyckoff_splitting",
"title": "Wyckoff splitting",
"x-optimade-type": "list",
"x-optimade-definition": {
"kind": "property",
"version": "0.1.0",
"format": "1.3",
"name": "wyckoff_splitting",
"label": "wyckoff_splitting_transformations"
},
"x-optimade-unit": "inapplicable",
"type": [
"array",
"null"
],
"description": "Wyckoff-position splitting data associated with a subgroup or same-space-group transform.\n\nEach list item gives the split of one parent Wyckoff position.\nThe parent Wyckoff letter is stored in the `parent` field rather than as a JSON dictionary key.\n\n**Requirements/Conventions**:\n\n- It MUST be a list of dictionaries.\n- Each dictionary MUST contain `parent`, the Wyckoff letter in the parent setting.\n- Each dictionary MUST contain `splits`, an ordered list of subgroup Wyckoff-position assignments, each carrying its target representative expression and exact affine map.\n\nFor an embedding `x_G = P*x_H + p`, the split records partition the parent orbit, expressed in the subgroup cell, into distinct subgroup orbits.\nFor each piece let `A` be the first three columns of `affine` and `b` its last column.\nThen `q_H = A*q_G + b`, where `q_G` is a fractional coordinate on the parent's published `first_orbit` branch and `q_H` is on the child's published representative branch.\nThe input is the actual parent representative coordinate, not its free-parameter vector; first evaluate the parent's `orbit[0]` map when starting from parameters.\nThe piece's `xyz` names the child representative branch and MUST equal that child's `first_orbit`; it is not a rendering of the piece's `affine` map on parent coordinates.\nRepeated child letters are meaningful: they identify different child orbits with the same Wyckoff type and MUST NOT be deduplicated by letter.\nFor generic parent parameters, expanding all split pieces under the subgroup gives disjoint orbits whose union is the transformed parent orbit in the subgroup cell.\nTheir multiplicities sum to `abs(det(P)) * parent_multiplicity`; this factor accounts for the cells and is not generally the full subgroup index.\nKeep the exact affine offsets when evaluating the maps; wrapping parent coordinates before applying a non-unimodular map can select a different child orbit.",
"items": {
"x-optimade-type": "dictionary",
"x-optimade-unit": "inapplicable",
"type": [
"object"
],
"description": "Splitting data for one parent Wyckoff position.",
"required": [
"parent",
"splits"
],
"properties": {
"parent": {
"x-optimade-type": "string",
"x-optimade-unit": "inapplicable",
"type": [
"string"
],
"description": "Parent Wyckoff letter."
},
"splits": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"type": [
"array"
],
"description": "Ordered split records for this parent Wyckoff letter.",
"items": {
"x-optimade-type": "dictionary",
"x-optimade-unit": "inapplicable",
"type": [
"object"
],
"description": "One Wyckoff split record.",
"required": [
"letter",
"xyz",
"affine"
],
"properties": {
"letter": {
"x-optimade-type": "string",
"x-optimade-unit": "inapplicable",
"type": [
"string"
],
"description": "Subgroup Wyckoff letter assigned by this split branch."
},
"xyz": {
"x-optimade-type": "string",
"x-optimade-unit": "inapplicable",
"type": [
"string"
],
"description": "Coordinate expression for the split branch."
},
"affine": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"x-optimade-dimensions": {
"names": [
"dim_lattice",
"dim_affine"
],
"sizes": [
3,
4
]
},
"type": [
"array"
],
"description": "Exact affine representation for the split branch as a 3 by 4 augmented matrix.\nEach row holds the three linear coefficients followed by the translation component, all as exact fraction strings.",
"items": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"x-optimade-dimensions": {
"names": [
"dim_affine"
],
"sizes": [
4
]
},
"type": [
"array"
],
"description": "One row of the augmented affine matrix.",
"items": {
"$id": "https://schemas.httk.org/defs/v0.1/properties/core/fraction",
"title": "Fraction",
"x-optimade-type": "string",
"x-optimade-definition": {
"label": "fraction_core",
"kind": "property",
"version": "0.1.0",
"format": "1.3",
"name": "fraction"
},
"type": [
"string",
"null"
],
"description": "A numerical representation formed as the quotient of two numbers represented as a string.",
"examples": [
"2/3",
"5/42",
"10",
"0"
],
"x-optimade-unit": "inapplicable"
}
}
}
}
}
}
}
},
"examples": [
[
{
"parent": "a",
"splits": [
{
"letter": "a",
"xyz": "x,y,z",
"affine": [
[
"1",
"0",
"0",
"0"
],
[
"0",
"1",
"0",
"0"
],
[
"0",
"0",
"1/2",
"0"
]
]
},
{
"letter": "a",
"xyz": "x,y,z",
"affine": [
[
"1",
"0",
"0",
"0"
],
[
"0",
"1",
"0",
"0"
],
[
"0",
"0",
"1/2",
"1/2"
]
]
}
]
}
]
]
},
"criteria": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"type": [
"array",
"null"
],
"description": "Backward-lift constraints for each parent Wyckoff position under this particular subgroup embedding.\nFor a fixed parent entry, every constraint MUST hold on the assigned subgroup representative coordinates modulo integer cell translations.\nThese are geometric coordinate conditions, conditional on the specified split roles and their Wyckoff branches; chemical species, occupancies, and matching an entire structure require separate checks.\nAn empty `constraints` list means no additional equations beyond the selected subgroup branches; it does not mean that no split roles are needed.\nThe first example is the generated I4/mmm (139) to P4/mmm (123) index-2 embedding: parent `a` splits into `a` and `d` with no equations, and parent `n` splits into `s` and `t` whose x and z coordinates must differ by 1/2 modulo 1.",
"items": {
"x-optimade-type": "dictionary",
"x-optimade-unit": "inapplicable",
"type": [
"object"
],
"description": "Backward-lift constraints for one parent Wyckoff position.",
"required": [
"parent",
"constraints"
],
"properties": {
"parent": {
"x-optimade-type": "string",
"x-optimade-unit": "inapplicable",
"type": [
"string"
],
"description": "Parent Wyckoff letter."
},
"constraints": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"type": [
"array"
],
"description": "Constraint records for this parent Wyckoff letter.",
"items": {
"x-optimade-type": "dictionary",
"x-optimade-unit": "inapplicable",
"type": [
"object"
],
"description": "One modular equation `sum_i dot(coeffs[i][0], q_i) = target[0] (mod 1)`.\nHere `q_i` is the three-component fractional coordinate on the published subgroup representative branch selected by `roles[i]`, not a local parameter vector or an arbitrary symmetry-equivalent site.\nThe current generator emits one scalar equation per record: `target` has length one, `coeffs` has one item per role, and each item contains one three-component row.\nThe coefficient entries are integer-valued exact strings, which makes the equation invariant under independent integer translations of the role coordinates.",
"properties": {
"roles": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"type": [
"array"
],
"description": "Wyckoff-position role references entering the constraint.",
"items": {
"x-optimade-type": "dictionary",
"x-optimade-unit": "inapplicable",
"type": [
"object"
],
"description": "One role reference.",
"required": [
"letter",
"index"
],
"properties": {
"letter": {
"x-optimade-type": "string",
"x-optimade-unit": "inapplicable",
"type": [
"string"
],
"description": "Wyckoff letter for the referenced role."
},
"index": {
"x-optimade-type": "integer",
"x-optimade-unit": "inapplicable",
"type": [
"integer"
],
"description": "Zero-based occurrence index among split pieces having this same letter in the corresponding parent's ordered `splits` list, not an index into all pieces or into the overall Wyckoff table."
}
}
}
},
"coeffs": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"type": [
"array"
],
"description": "Exact integer-valued coefficient rows, in the same order as `roles`.",
"items": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"type": [
"array"
],
"description": "Coefficients associated with one role.",
"items": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"x-optimade-dimensions": {
"names": [
"dim_lattice"
],
"sizes": [
3
]
},
"type": [
"array"
],
"description": "One exact coefficient vector.",
"items": {
"$id": "https://schemas.httk.org/defs/v0.1/properties/core/fraction",
"title": "Fraction",
"x-optimade-type": "string",
"x-optimade-definition": {
"label": "fraction_core",
"kind": "property",
"version": "0.1.0",
"format": "1.3",
"name": "fraction"
},
"type": [
"string",
"null"
],
"description": "A numerical representation formed as the quotient of two numbers represented as a string.",
"examples": [
"2/3",
"5/42",
"10",
"0"
],
"x-optimade-unit": "inapplicable"
}
}
}
},
"target": {
"x-optimade-type": "list",
"x-optimade-unit": "inapplicable",
"type": [
"array"
],
"description": "One-element list containing the exact right-hand side modulo one, normalized to the interval [0,1).",
"items": {
"$id": "https://schemas.httk.org/defs/v0.1/properties/core/fraction",
"title": "Fraction",
"x-optimade-type": "string",
"x-optimade-definition": {
"label": "fraction_core",
"kind": "property",
"version": "0.1.0",
"format": "1.3",
"name": "fraction"
},
"type": [
"string",
"null"
],
"description": "A numerical representation formed as the quotient of two numbers represented as a string.",
"examples": [
"2/3",
"5/42",
"10",
"0"
],
"x-optimade-unit": "inapplicable"
}
}
}
}
}
}
}
}
},
"examples": [
{
"index": 2,
"subgroup_type": "k",
"k_subtype": "loss_of_centering_translation",
"affine_transformation": {
"matrix": [
[
"1",
"0",
"0"
],
[
"0",
"1",
"0"
],
[
"0",
"0",
"1"
]
],
"vector": [
"0",
"0",
"0"
],
"xyz": "x,y,z"
},
"wyckoff_splitting": [
{
"parent": "a",
"splits": [
{
"letter": "a",
"xyz": "0,0,0",
"affine": [
[
"1",
"0",
"0",
"0"
],
[
"0",
"1",
"0",
"0"
],
[
"0",
"0",
"1",
"0"
]
]
},
{
"letter": "d",
"xyz": "1/2,1/2,1/2",
"affine": [
[
"1",
"0",
"0",
"1/2"
],
[
"0",
"1",
"0",
"1/2"
],
[
"0",
"0",
"1",
"1/2"
]
]
}
]
},
{
"parent": "n",
"splits": [
{
"letter": "s",
"xyz": "x,0,z",
"affine": [
[
"0",
"-1",
"0",
"0"
],
[
"-1",
"0",
"0",
"0"
],
[
"0",
"0",
"-1",
"0"
]
]
},
{
"letter": "t",
"xyz": "x,1/2,z",
"affine": [
[
"0",
"-1",
"0",
"1/2"
],
[
"-1",
"0",
"0",
"1/2"
],
[
"0",
"0",
"-1",
"1/2"
]
]
}
]
}
],
"criteria": [
{
"parent": "a",
"constraints": []
},
{
"parent": "n",
"constraints": [
{
"roles": [
{
"letter": "s",
"index": 0
},
{
"letter": "t",
"index": 0
}
],
"coeffs": [
[
[
"0",
"0",
"1"
]
],
[
[
"0",
"0",
"-1"
]
]
],
"target": [
"1/2"
]
},
{
"roles": [
{
"letter": "s",
"index": 0
},
{
"letter": "t",
"index": 0
}
],
"coeffs": [
[
[
"1",
"0",
"0"
]
],
[
[
"-1",
"0",
"0"
]
]
],
"target": [
"1/2"
]
}
]
}
]
},
{
"affine_transformation": {
"matrix": [
[
"-1",
"0",
"0"
],
[
"0",
"-1",
"0"
],
[
"0",
"0",
"-1"
]
],
"vector": [
"0",
"0",
"0"
],
"xyz": "-x,-y,-z",
"det": -1,
"is_orthogonal": true
},
"compatible_systems": [
"triclinic",
"monoclinic",
"orthorhombic",
"tetragonal",
"trigonal",
"hexagonal",
"cubic"
],
"operation_kind": "affine"
}
]
}
}
},
"examples": [
{
"normalizer_kind": "orthogonal_affine",
"representation": "orthogonal_coset_representatives",
"candidate_set": "signed_permutation_matrices",
"n_symops": 1,
"n_linear_parts": 1,
"n_raw_candidates": 96,
"n_coset_representatives": 1,
"bounds": {
"det_abs": 1,
"max_abs_linear_entry": 1
},
"symops": [
{
"compatible_systems": [
"triclinic",
"monoclinic",
"orthorhombic",
"tetragonal",
"trigonal",
"hexagonal",
"cubic"
],
"affine_transformation": {
"matrix": [
[
"-1",
"0",
"0"
],
[
"0",
"-1",
"0"
],
[
"0",
"0",
"-1"
]
],
"vector": [
"1/2",
"1/2",
"1/2"
],
"xyz": "-x+1/2,-y+1/2,-z+1/2",
"det": -1,
"is_orthogonal": true
},
"operation_kind": "orthogonal_affine"
}
]
}
]
}