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/spacegroups/structure_seminvariants
Definition name: structure_seminvariants
Property name: Structure seminvariants
Description: Structure-seminvariant vectors and moduli for the space-group setting, describing allowed changes of origin that preserve its symmetry description.
Type: list
These are useful for phase-origin constraints in structure determination and for comparing origin choices; they also enter cctbx's FFT gridding restrictions.
For a Miller-index column h, the phase of a reflection is a structure seminvariant precisely when every listed pair (v,m) satisfies v dot h = 0 (mod m) for m > 0, or v dot h = 0 as an ordinary equality for m = 0.
A positive modulus describes a discrete allowed origin shift v/m; modulus zero describes arbitrary continuous shifts parallel to v, not division by zero.
These restrictions concern phase changes under allowed origins; they are not systematic-absence conditions on reflection intensities.
Requirements/Conventions:
It MUST be a list of dictionaries, each with the following keys:
vector: REQUIRED; List of 3 Integers. Structure-seminvariant vector in the fractional-coordinate basis, paired with Miller indices in its reciprocal basis.
modulus: REQUIRED; Integer. Positive modulus for a discrete shift, or zero for a continuous origin-shift direction.
Examples:
[{"vector": [1, 0, 0], "modulus": 0}, {"vector": [0, 1, 0], "modulus": 0}, {"vector": [0, 0, 1], "modulus": 0}][{"vector": [1, 0, 0], "modulus": 2}, {"vector": [0, 1, 0], "modulus": 2}, {"vector": [0, 0, 1], "modulus": 2}]JSON definition:
{
"$id": "https://schemas.httk.org/defs/v0.1/properties/spacegroups/structure_seminvariants",
"$schema": "https://schemas.optimade.org/meta/v1.3/optimade/property_definition.json",
"title": "Structure seminvariants",
"x-optimade-type": "list",
"x-optimade-definition": {
"kind": "property",
"version": "0.1.0",
"format": "1.3",
"name": "structure_seminvariants",
"label": "structure_seminvariants_spacegroups"
},
"type": [
"array",
"null"
],
"description": "Structure-seminvariant vectors and moduli for the space-group setting, describing allowed changes of origin that preserve its symmetry description.\n\nThese are useful for phase-origin constraints in structure determination and for comparing origin choices; they also enter cctbx's FFT gridding restrictions.\nFor a Miller-index column h, the phase of a reflection is a structure seminvariant precisely when every listed pair `(v,m)` satisfies `v dot h = 0 (mod m)` for `m > 0`, or `v dot h = 0` as an ordinary equality for `m = 0`.\nA positive modulus describes a discrete allowed origin shift `v/m`; modulus zero describes arbitrary continuous shifts parallel to v, not division by zero.\nThese restrictions concern phase changes under allowed origins; they are not systematic-absence conditions on reflection intensities.\n\n**Requirements/Conventions**:\n\n- It MUST be a list of dictionaries, each with the following keys:\n\n - **vector**: REQUIRED; List of 3 Integers.\n Structure-seminvariant vector in the fractional-coordinate basis, paired with Miller indices in its reciprocal basis.\n\n - **modulus**: REQUIRED; Integer.\n Positive modulus for a discrete shift, or zero for a continuous origin-shift direction.",
"x-optimade-unit": "inapplicable",
"items": {
"x-optimade-type": "dictionary",
"type": [
"object",
"null"
],
"description": "One structure-seminvariant condition vector.",
"properties": {
"vector": {
"x-optimade-type": "list",
"x-optimade-dimensions": {
"names": [
"dim_lattice"
],
"sizes": [
3
]
},
"type": [
"array",
"null"
],
"description": "Integer vector defining the seminvariant congruence.",
"items": {
"x-optimade-type": "integer",
"type": [
"integer",
"null"
],
"description": "One vector component.",
"x-optimade-unit": "inapplicable"
},
"x-optimade-unit": "inapplicable"
},
"modulus": {
"x-optimade-type": "integer",
"type": [
"integer",
"null"
],
"description": "Positive modulus for the discrete seminvariant congruence, or zero for an exact equality associated with a continuous allowed shift.",
"x-optimade-unit": "inapplicable"
}
},
"x-optimade-unit": "inapplicable"
},
"examples": [
[
{
"vector": [
1,
0,
0
],
"modulus": 0
},
{
"vector": [
0,
1,
0
],
"modulus": 0
},
{
"vector": [
0,
0,
1
],
"modulus": 0
}
],
[
{
"vector": [
1,
0,
0
],
"modulus": 2
},
{
"vector": [
0,
1,
0
],
"modulus": 2
},
{
"vector": [
0,
0,
1
],
"modulus": 2
}
]
]
}