A toplevel crystallography ontology based on EMMO and the CIF core dictionary. It is implemented as a formal language.
Label of corresponding entity in the core CIF dictionary. See https://www.iucr.org/resources/cif/dictionaries/cif_core
cifLabel
URL to corresponding entity in the core CIF dictionary. See https://www.iucr.org/resources/cif/dictionaries/cif_core
cifMatch
The word "constituent" means part of a whole. Within the crystallography domain, constituents are defined as the real-world building blocks of a crystal (i.e. atoms or molecules).
Constituent
Fractional position of a site along the b direction.
FractionalPositionB
The angle between lattice vectors `a` and `c`, where lattice vectors `a`, `b` and `c` defines the unit cell,
LatticeParameterBeta
The length of lattice vectors `a`, where lattice vectors `a`, `b` and `c` defines the unit cell,
LatticeParameterA
A crystal system with 1 sixfold axes of rotation.
Hexagonal
The occupancy of a site. Must be a number between zero and one.
Occupancy
The angle between lattice vectors `b` and `c`, where lattice vectors `a`, `b` and `c` defines the unit cell,
LatticeParameterAlpha
The number of different sites that are generated by the application of the space-group symmetry to the coordinates given for this site.
SymmetryMultiplicity
A symbol that stands for a crystallographical concept in the language of the crystallographical domain.
CrystallographicSymbol
A crystal is a solid whos constituents are ordered.
Crystal
The crystal structure describes of the ordered arrangement of species in a crystal.
CrystalStructure
A vector connecting two lattice sites, where the lattice sites defines the periodic structure of a crystal.
LatticeVector
A number between 1 and 230 that uniquely identifies the space group.
Even though the spacegroups are unique, it is possible to choose the origin and basis differently resulting in different settings.
SpacegroupNumber
A crystal system with 1 threefold axes of rotation.
Trigonal
The symbolic object defining the basis for crystallography.
Crystallographical
A periodic unit in a crystal structure. It is spanned by three lattice vectors.
A unit cell is ca be described by either specifying the three lattice vectors that it is spanned by, or by 6 the lattice parameters (the length of and angles between the 3 lattice vectors).
UnitCell
The length of lattice vectors `b`, where lattice vectors `a`, `b` and `c` defines the unit cell,
LatticeParameterB
Shape3x3Matrix
A parsable string giving one of the symmetry operations of the space group in algebraic form.
If 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 fractions, an equivalent position X' is generated from a given position X by the equation X' = W X + w
When a list of symmetry operations is given, it must contain a complete set of coordinate representatives which generates all the operations of the space group by the addition of all primitive translations of the space group. Such representatives are to be found as the coordinates of the general-equivalent position in International Tables for Crystallography Vol. A (2002), to which it is necessary to add any centring translations shown above the general-equivalent position. That is to say, it is necessary to list explicitly all the symmetry operations required to generate all the atoms in the unit cell defined by the setting used.
SymmetryOperationString
Volume of the unit cell.
CellVolume
A crystal system with no symmetry axis.
Triclinic
The length of lattice vectors `c`, where lattice vectors `a`, `b` and `c` defines the unit cell,
LatticeParameterC
A number that stands for the space group setting, i.e. the choice of origin (and basis).
Typically the space group setting is represented as "1" for the standard setting and "2" for the alternative setting. The setting number does not appear in the CIF core dictionary, but is included in International Tables. The CIF core dictionary recommends usint the '_space_group_crystal_system' instead.
SpacegroupSettingNumber
ChemicalSpecies
A chemical species is a well defined set of one or more atoms/ions. The chemical species can be atom, molecule, ion, radical, and it has a chemical name and chemical formula. The chemical species are associated to the crystalline site in a structure. Note that two otherwise identical molecules with differing orientation in the unit cell will be considered two different species.
Species
A unique identifier for a particular site in the crystal.
SiteLabel
Fractional position of a site along the a direction.
FractionalPositionA
A rotation matrix.
The determinant of a rotation matrix is one.
RotationMatrix
A crystal system with 4 threefold axes of rotation.
Cubic
A crystal system with 1 fourfold axes of rotation.
Tetragonal
A translation vector.
TranslationVector
A symmetry operation is an action that leaves an object looking the same after it has been carried out. Mathematically it is described by a rotation followed by a translation.
For example, if we take a molecule of water and rotate it by 180° about an axis passing through the central O atom (between the two H atoms) it will look the same as before.
SymmetryOperation
A position expressed in fractional coordinates with respect to an origin and three spatial vectors.
FractionalPosition
A crystal system with 3 twofold axes of rotation or 1 twofold axis of rotation and 2 mirror planes.
Orthorhombic
The angle between lattice vectors `a` and `b`, where lattice vectors `a`, `b` and `c` defines the unit cell,
LatticeParameterGamma
Fractional position of a site along the c direction.
FractionalPositionC
A crystal system with 1 twofold axes of rotation or 1 mirror plane.
Monoclinic
A symbol that uniquely defines the space group and its reference to a particular coordinate system. References: - Hall, S. R. (1981). Acta Cryst. A37, 517-525; erratum (1981), A37, 921. - International Tables for Crystallography, Vol. B (2001), Chapter 1.4, Appendix 1.4.2
HallSymbol
The 6 parameters defining the unit cell; a, b, c, alpha, beta, gamma, where a, b, c are the lengths of the 3 lattice vectors spanning the unit cell and alpha, beta, gamma are the angles between them.
LatticeParameter
A site within a unit cell related to the position of a species.
Site
The symmetry group that represents the symmetry of a crystal, in terms of the set of all its symmetry operations.
A spacegroup is commonly identified by its number as given in International Tables for Crystallography Vol. A. Specific settings of the space groups can be identified either by their Hall symbol or by specifying their symmetry operations. Specific settings listed in International Tables for Crystallography Vol. A, may also be specified by specifying the setting number in combination with the space group number or Hermann-Mauguin symbol. The commonly used Hermann-Mauguin symbol determines the space-group type uniquely but several different Hermann-Mauguin symbols may refer to the same space-group type. A Hermann-Mauguin symbol contains information on the choice of the basis, but not on the choice of origin. Different formats for the Hermann-Mauguin symbol are found in the symmetry CIF dictionary.
Spacegroup
The Wyckoff symbol (letter) as listed in the space-group tables of International Tables for Crystallography Vol. A (2002).
WyckoffSymbol
A symbol that uniquely determines the space group.
Note that a given spacegroup may be described by more than one Hermann Mauguin symbol. Spacegroups are therefore best described by spacegroup number.
The Hermann-Mauguin symbol may contain information on the choice of basis, but not on the choice of origin. To define the setting uniquely, use _space_group_name_Hall or list the symmetry operations.
HermannMauguinSymbol
The smallest unit cell that contains the same point group symmetries as the overall lattice.
The conventional unit cell is the one that is referred to in International Tables for Crystallography vol. A.
ConventionalUnitCell
The name of the system of geometric crystal classes of space groups (crystal system) to which the space group belongs.
There are 7 crystal systems.
CrystalSystem
A unit cell that contains exactly one lattice point. It is the smallest possible cell.
There may be several choices of primitive unit cell, hence it is not unique.
PrimitiveUnitCell