## elastic-constants-isothermal-cubic-crystal-npt

Property Definition (short name) A common way to refer to the Property Definition. Note there may be multiple Property Definitions with the same short name, to fully distinguish between Property Definitions the full Tag URI must be used (the Property Definition ID). elastic-constants-isothermal-cubic-crystal-npt tag:staff@noreply.openkim.org,2014-05-21:property/elastic-constants-isothermal-cubic-crystal-npt Isothermal elastic constants for a cubic crystal at constant temperature and stress The three independent isothermal elastic constants c11, c12 and c44 for a cubic crystal at a constant given temperature and stress. (The elastic constants are the 2nd derivatives of the strain energy density with respect to strain.) karls karls 2014-05-21 Property Definition Physics Validator Property Documentation Wiki
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#### Property Definition Keys

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#### a

type float true [] true Average equilibrium conventional lattice constant of the cubic crystal.

#### basis-atom-coordinates

type float false [":" 3] true Fractional coordinates of the basis atoms in the conventional unit cell. If the unit cell vectors are denoted by , , and , and the fractional coordinates of atom 'i' are [afrac_i, bfrac_i, cfrac_i], the value of 'basis-atom-coordinates' will be of the form [[afrac_1 bfrac_1 cfrac_1] [afrac_2 bfrac_2 cfrac_2] ... ]. All components of each basis atom should be between zero and one, inclusive of zero.

#### c11

type float true [] true The 11 component of the isothermal elasticty matrix in Voigt notation, which corresponds to the 1111 component of the 4th order elasticity tensor. The orthonormal basis used to express the tensor should be aligned with the cubic 4-fold axes of the crystal.

#### c12

type float true [] true The 12 component of the isothermal elasticty matrix in Voigt notation, which corresponds to the 1122 component of the 4th order elasticity tensor. The orthonormal basis used to express the tensor should be aligned with the cubic 4-fold axes of the crystal.

#### c44

type float true [] true The 44 component of the isothermal elasticty matrix in Voigt notation, which corresponds to the 2323 component of the 4th order elasticity tensor. The orthonormal basis used to express the tensor should be aligned with the cubic 4-fold axes of the crystal.

#### cauchy-stress

type float true [6] true The [xx,yy,zz,yz,xz,xy] (i.e. [11,22,33,23,13,12]) components of the Cauchy stress acting on the periodic cell. The orthonormal basis used to express the stress should be aligned with the cubic 4-fold axes of the crystal and the expected form of the stress tensor should be [d d d 0 0 0], where d > 0 indicates tensile stress.

#### species

type string false [":"] true The element symbols of the basis atoms. The order in which the species are specified must correspond to the order of the atoms listed in 'basis-atom-coordinates'.

#### temperature

type float true [] true Temperature of the crystal.

#### excess

type float true [] false Total square numerical asymmetry of the calculated elastic constants, in Voigt notation, \sqrt{ \sum_{i>j} (\C_{ij} - \C_{ji})^2 }

#### short-name

type string false [":"] false Short name defining the cubic crystal type.

#### space-group

type string false [] false Hermann-Mauguin designation for the space group associated with the symmetry of the crystal (e.g. Immm, Fm-3m, P6_3/mmc).

#### wyckoff-coordinates

type float false [":" 3] false Coordinates of the unique Wyckoff sites used in the fully symmetry-reduced description of the crystal, given as fractions of the lattice vectors. The order of elements in this array must correspond to the order of the entries listed in 'wyckoff-species' and 'wyckoff-multiplicity-and-letter'.

#### wyckoff-multiplicity-and-letter

type string false [":"] false Multiplicity and standard letter of the unique Wyckoff sites used in the fully symmetry-reduced description of the crystal (e.g. 4a, 2b). Note that the sum of the Wyckoff multiplicities should equal the total number of elements in 'basis-atom-coordinates'. The order of elements in this array must correspond to the order of the entries listed in 'wyckoff-species' and 'wyckoff-coordinates'.

#### wyckoff-species

type string false [":"] false The element symbol of the atomic species of the unique Wyckoff sites used in the fully symmetry-reduced description of the crystal. The order of the entries must correspond to the order of the entries in 'wyckoff-multiplicity-and-letter' and 'wyckoff-coordinates'.

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