2.3.3.3.169. NXunit_cell

Status:

base class (contribution), extends NXobject

Description:

Base class to describe structural aspects of an arrangement of ...

Base class to describe structural aspects of an arrangement of atoms or ions including a crystallographic unit cell.

Following recommendations of CIF and International Tables of Crystallography.

Symbols:

d: Dimensionality of the lattice.

Groups cited:

NXatom

Structure:

reference_frame: (optional) NX_CHAR

Path to a reference frame in which the unit cell is defined ...

Path to a reference frame in which the unit cell is defined to resolve ambiguity in cases when e.g. a different reference frame than the NeXus default reference frame (McStas) was chosen.

dimensionality: (optional) NX_POSINT

Dimensionality of the structure. ...

Dimensionality of the structure.

Any of these values: 1 | 2 | 3

a_b_c: (optional) NX_NUMBER (Rank: 1, Dimensions: [d]) {units=NX_LENGTH}

Geometry of the unit cell quantified via parameters a, b, and c.

alpha_beta_gamma: (optional) NX_NUMBER (Rank: 1, Dimensions: [d]) {units=NX_ANGLE}

Geometry of the unit cell quantified via parameters alpha, beta, and gamma.

crystal_system: (optional) NX_CHAR

Crystal system. ...

Crystal system.

For a crystal system in 2D space monoclinic is an exact synonym for oblique. For a crystal system in 2D space orthorhombic is an exact synonym for rectangular. For a crystal system in 2D space tetragonal is an exact synonym for square.

Any of these values:

  • triclinic

  • monoclinic

  • orthorhombic

  • tetragonal

  • rhombohedral

  • hexagonal

  • cubic

laue_group: (optional) NX_CHAR

Laue group using International Table of Crystallography notation.

point_group: (optional) NX_CHAR

Point group using International Table of Crystallography notation.

space_group: (optional) NX_CHAR

Space group from the International Table of Crystallography notation.

is_centrosymmetric: (optional) NX_BOOLEAN

True if space group is considered a centrosymmetric one. ...

True if space group is considered a centrosymmetric one. False if space group is considered a non-centrosymmetric one.

Centrosymmetric has all types and combinations of symmetry elements (translation, rotational axis, mirror planes, center of inversion) Non-centrosymmetric compared to centrosymmetric is constrained (no inversion). Chiral compared to non-centrosymmetric is constrained (no mirror planes).

is_chiral: (optional) NX_BOOLEAN

True if space group is considered a chiral one. ...

True if space group is considered a chiral one. False if space group is consider a non-chiral one.

area: (optional) NX_NUMBER {units=NX_AREA}

Area of the unit cell if dimensionality is 2.

volume: (optional) NX_NUMBER {units=NX_VOLUME}

Volume of the unit cell if dimensionality is 3.

ATOM: (optional) NXatom

Hypertext Anchors

List of hypertext anchors for all groups, fields, attributes, and links defined in this class.

NXDL Source:

https://github.com/FAIRmat-NFDI/nexus_definitions/tree/fairmat/contributed_definitions/NXunit_cell.nxdl.xml