This page documents an OPTIMADE Property Definition. See https://schemas.optimade.org/ for more information.
ID: https://schemas.optimade.org/defs/v1.3/properties/optimade/trajectories/fractional_site_positions
Definition name: fractional_site_positions
Property name: list of fractional site positions
Description: A list of fractional_site_positions items.
A fractional_site_positions item is the Fractional coordinates (positions) of each site in the structure.
Type: list
For each fractional_site_positions item the following applies:
A site is usually used to describe positions of atoms; what atoms can be encountered at a given site is conveyed by the species_at_sites property, and the species themselves are described in the species property.
Site coordinates MAY be given as cartesian_site_positions, fractional_site_positions, or both.
When symmetry operations given in space_group_symmetry_operations_xyz are applied, they MUST be applied to coordinates given in the fractional_site_positions array.
Requirements/Conventions:
lattice_vectors property.assemblies).cartesian_site_positions and the fractional_site_positions always describe the same sites, they MUST always have the same number of elements, equal to the number of elements in the species_at_sites array.Explained examples:
[[0,0,0],[0,0,0.2]] indicates a structure with two sites, one sitting at the origin and one along the third unit cell axis (c-axis), 1/5-th (0.2) of the vector c in the direction of the vector c from the origin.Examples:
[[[0, 0, 0], [0, 0, 0.2]], [[0, 0, 1.3], [0, 0, 2.1]]]JSON definition:
{
"$id": "https://schemas.optimade.org/defs/v1.3/properties/optimade/trajectories/fractional_site_positions",
"$schema": "https://schemas.optimade.org/meta/v1.3/optimade/property_definition.json",
"title": "list of fractional site positions",
"x-optimade-type": "list",
"x-optimade-definition": {
"label": "fractional_site_positions_optimade_trajectories",
"kind": "property",
"version": "1.3.0",
"format": "1.3",
"name": "fractional_site_positions"
},
"x-optimade-dimensions": {
"names": [
"dim_frames",
"dim_sites",
"dim_spatial"
],
"sizes": [
null,
null,
3
],
"compactable": [
"constant",
"no",
"no"
]
},
"type": [
"array",
"null"
],
"description": "A list of fractional_site_positions items.\nA fractional_site_positions item is the Fractional coordinates (positions) of each site in the structure.\n\nFor each fractional_site_positions item the following applies:\n\nA site is usually used to describe positions of atoms; what atoms can be encountered at a given site is conveyed by the `species_at_sites` property, and the species themselves are described in the `species` property.\nSite coordinates MAY be given as `cartesian_site_positions`, `fractional_site_positions`, or both.\nWhen symmetry operations given in `space_group_symmetry_operations_xyz` are applied, they MUST be applied to coordinates given in the `fractional_site_positions` array.\n\n**Requirements/Conventions**:\n\n- It MUST be a list of length equal to the number of sites in the structure, where every element is a list of the three fractional coordinates of a site expressed as float values in the fractions of the unit cell vectors given by the `lattice_vectors` property.\n- An entry MAY have multiple sites at the same site position (for a relevant use of this, see e.g., the property `assemblies`).\n- Since both `cartesian_site_positions` and the `fractional_site_positions` always describe the same sites, they MUST always have the same number of elements, equal to the number of elements in the `species_at_sites` array.\n\n**Explained examples**:\n\n- `[[0,0,0],[0,0,0.2]]` indicates a structure with two sites, one sitting at the origin and one along the third unit cell axis (*c*-axis), 1/5-th (0.2) of the vector *c* in the direction of the vector *c* from the origin.",
"examples": [
[
[
[
0,
0,
0
],
[
0,
0,
0.2
]
],
[
[
0,
0,
1.3
],
[
0,
0,
2.1
]
]
]
],
"x-optimade-unit": "inapplicable",
"items": {
"$id": "https://schemas.optimade.org/defs/v1.3/properties/optimade/structures/fractional_site_positions",
"title": "fractional site positions",
"x-optimade-type": "list",
"x-optimade-definition": {
"label": "fractional_site_positions_optimade_structures",
"kind": "property",
"version": "1.3.0",
"format": "1.2",
"name": "fractional_site_positions"
},
"x-optimade-dimensions": {
"names": [
"dim_sites",
"dim_spatial"
],
"sizes": [
null,
3
]
},
"type": [
"array",
"null"
],
"description": "Fractional coordinates (positions) of each site in the structure.\n\nA site is usually used to describe positions of atoms; what atoms can be encountered at a given site is conveyed by the `species_at_sites` property, and the species themselves are described in the `species` property.\nSite coordinates MAY be given as `cartesian_site_positions`, `fractional_site_positions`, or both.\nWhen symmetry operations given in `space_group_symmetry_operations_xyz` are applied, they MUST be applied to coordinates given in the `fractional_site_positions` array.\n\n**Requirements/Conventions**:\n\n- It MUST be a list of length equal to the number of sites in the structure, where every element is a list of the three fractional coordinates of a site expressed as float values in the fractions of the unit cell vectors given by the `lattice_vectors` property.\n- An entry MAY have multiple sites at the same site position (for a relevant use of this, see e.g., the property `assemblies`).\n- Since both `cartesian_site_positions` and the `fractional_site_positions` always describe the same sites, they MUST always have the same number of elements, equal to the number of elements in the `species_at_sites` array.\n\n**Explained examples**:\n\n- `[[0,0,0],[0,0,0.2]]` indicates a structure with two sites, one sitting at the origin and one along the third unit cell axis (*c*-axis), 1/5-th (0.2) of the vector *c* in the direction of the vector *c* from the origin.",
"examples": [
[
[
0,
0,
0
],
[
0,
0,
0.2
]
]
],
"x-optimade-unit": "inapplicable",
"items": {
"x-optimade-type": "list",
"x-optimade-dimensions": {
"names": [
"dim_spatial"
],
"sizes": [
3
]
},
"type": [
"array"
],
"x-optimade-unit": "inapplicable",
"items": {
"x-optimade-type": "float",
"type": [
"number"
],
"x-optimade-unit": "dimensionless"
}
}
}
}