This page documents an OPTIMADE Property Definition. See https://schemas.optimade.org/ for more information.

**ID: https://schemas.optimade.org/defs/v1.2/properties/optimade/structures/cartesian_site_positions**

`cartesian_site_positions`

**Property name:** Cartesian site positions

**Description:** Cartesian positions of each site in the structure.

**Type:** list

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.

**Requirements/Conventions**:

- 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 Cartesian coordinates of a site expressed as float values in the unit angstrom (Å).
- An entry MAY have multiple sites at the same Cartesian position (for a relevant use of this, see e.g., the property
`assemblies`

).

**Explained examples**:

`[[0,0,0],[0,0,2]]`

indicates a structure with two sites, one sitting at the origin and one along the (positive)*z*-axis, 2 Å away from the origin.

**Examples:**

`[[0, 0, 0], [0, 0, 2]]`

**JSON definition:**

```
{
"$id": "https://schemas.optimade.org/defs/v1.2/properties/optimade/structures/cartesian_site_positions",
"$schema": "https://schemas.optimade.org/meta/v1.2/optimade/property_definition.json",
"title": "Cartesian site positions",
"x-optimade-type": "list",
"x-optimade-definition": {
"label": "cartesian_site_positions_optimade_structures",
"kind": "property",
"version": "1.2.0",
"format": "1.2",
"name": "cartesian_site_positions"
},
"x-optimade-unit-definitions": [
{
"$id": "https://schemas.optimade.org/defs/v1.2/units/si/general/angstrom",
"title": "\u00e5ngstr\u00f6m",
"symbol": "angstrom",
"display-symbol": "\u00c5",
"description": "A unit of length equal to 10\u207b\u00b9\u2070 meter, using the current, or one of the historical, definitions of the SI units.\n\nThe \u00e5ngstr\u00f6m unit appears in the International System of Units (SI), 1st ed. (1970) defined as \"1 \u00c5 = 0.1 nm = 10\u207b\u00b9\u2070 m\".\n\nThe \u00e5ngstr\u00f6m unit was implicitly redefined via the redefinition of the metre at the 17th CGPM meeting (1983), resolution 1.\n\n- The International System of Units (SI), 1st ed. (1970) categorizes the unit as \"temporarily admitted\" for use with the SI units.\n- The International System of Units (SI), 7th ed. (1998) changes the categorisation to \"Other non-SI units currently accepted for use with the International System.\"\n- The International System of Units (SI), 8th ed. (2006) changes the categorization to \"Other non-SI units\" and adds as a clarifying footnote \"The \u00e5ngstr\u00f6m is widely used by x-ray crystallographers and structural chemists because all chemical bonds lie in the range 1 to 3 \u00e5ngstr\u00f6ms. However it has no official sanction from the CIPM or the CGPM.\"\n- The \u00e5ngstr\u00f6m is omitted in the International System of Units (SI), 9th Edition (2019).\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": [
"https://schemas.optimade.org/defs/v1.2/units/si/1970/temporary/angstrom",
"https://schemas.optimade.org/defs/v1.2/units/si/1983/temporary/angstrom"
],
"resources": [
{
"relation": "Definition in the International System of Units (SI), 1st Edition",
"resource-id": "https://www.bipm.org/en/publications/si-brochure"
},
{
"relation": "Redefinition of the metre at the 17th CGPM meeting (1983), resolution 1",
"resource-id": "https://www.bipm.org/en/committees/cg/cgpm/17-1983/resolution-1"
},
{
"relation": "Wikipedia article describing the unit",
"resource-id": "https://en.wikipedia.org/wiki/Angstrom"
}
],
"defining-relation": {
"base-units": [
{
"symbol": "m",
"id": "https://schemas.optimade.org/defs/v1.2/units/si/general/metre"
}
],
"base-units-expression": "m",
"scale": {
"exponent": -10
}
},
"x-optimade-definition": {
"label": "angstrom_si_general",
"kind": "unit",
"format": "1.2",
"version": "1.2.0",
"name": "angstrom"
}
}
],
"x-optimade-dimensions": {
"names": [
"dim_sites",
"dim_spatial"
],
"sizes": [
null,
3
]
},
"type": [
"array",
"null"
],
"description": "Cartesian 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.\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 Cartesian coordinates of a site expressed as float values in the unit angstrom (\u00c5).\n- An entry MAY have multiple sites at the same Cartesian position (for a relevant use of this, see e.g., the property `assemblies`).\n\n**Explained examples**:\n\n- `[[0,0,0],[0,0,2]]` indicates a structure with two sites, one sitting at the origin and one along the (positive) *z*-axis, 2 \u00c5 away from the origin.",
"examples": [
[
[
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": "angstrom"
}
}
}
```