dislocation-core-energy-cubic-crystal-npt


Property Definition (short name)
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dislocation-core-energy-cubic-crystal-npt
Property Definition ID
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tag:staff@noreply.openkim.org,2021-02-24:property/dislocation-core-energy-cubic-crystal-npt
Title
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Dislocation core energy of a cubic crystal at zero temperature and a given stress state
Description
A description about this Property Definition.
The dislocation core energy is a mathematical construct designed to remove the singularity in the stress and strain fields of elasticity theory. The total strain energy is computed relative to the cohesive energy of the ideal crystal, and the core energy is the portion of this energy that is not accounted for by an elastic model. In this property, the dislocation core energy for cubic crystals at zero temperature and a given stress state is reported using three different elastic models: nonsingular, isotropic, and anisotropic. Each of these core energies is computed for a range of dislocation core cutoff radii and is given in units of energy per unit dislocation line length.
Contributor
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qyc081025
Maintainer
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qyc081025
Creation date
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2021-02-24
Content on GitHub
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Property Definition Keys


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a

typefloat
has-unittrue
extent[]
requiredtrue
descriptionEquilibrium conventional lattice constant of the cubic crystal.

basis-atom-coordinates

typefloat
has-unitfalse
extent[":" 3]
requiredtrue
descriptionFractional coordinates of the basis atoms in the conventional unit cell. If the unit cell vectors are denoted by <a>, <b>, and <c>, 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.

burgers-vector-direction

typefloat
has-unitfalse
extent[3]
requiredtrue
descriptionThe Burgers vector of the dislocation given as a vector of three real numbers relative to the lattice parameter, e.g. [0.5, 0.5, 0] corresponds to a Burgers vectors of [a/2, a/2, 0].

cauchy-stress

typefloat
has-unittrue
extent[6]
requiredtrue
descriptionThe [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.

core-energy-anisotropic

typefloat
has-unittrue
extent[":"]
requiredtrue
descriptionThe core energy calculated using the classical theory of anisotropic elasticity using a finite dislocation core cutoff radius.

core-energy-isotropic

typefloat
has-unittrue
extent[":"]
requiredtrue
descriptionThe core energy calculated using the classical theory of isotropic elasticity using a finite dislocation core cutoff radius.

core-energy-nonsingular

typefloat
has-unittrue
extent[":"]
requiredtrue
descriptionThe core energy calculated using the (isotropic) nonsingular theory of elasticity. This is computed by spreading the Burgers vector isotropically around the dislocation line in the region defined by the core radius. For reference, see W. Cai, A. Arsenlis, C. R. Weinberger, and V. V. Bulatov, A non-singular continuum theory of dislocations, JMPS 54, 561 (2006).

dislocation-core-radius

typefloat
has-unitfalse
extent[":"]
requiredtrue
descriptionThe physical region where atoms present a radically distinct local order with respect to the bulk. This parameter is given in terms of the magnitude of the Burgers vector, e.g. a value of 0.5 defines a core region of radius b/2 where b is the magnitude of the Burgers vector.

dislocation-line-direction

typeint
has-unitfalse
extent[3]
requiredtrue
descriptionThe crystallographic direction of the dislocation line direction given as a vector of three integers, e.g. [1, 1, 2].

slip-plane-miller-indices

typeint
has-unitfalse
extent[3]
requiredtrue
descriptionThe vector of Miller indices defining the slip plane of the dislocation, e.g. [1, 1, 1].

species

typestring
has-unitfalse
extent[":"]
requiredtrue
descriptionThe 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'.

relaxed-core-positions

typefloat
has-unittrue
extent[":" 3]
requiredfalse
descriptionThe [x,y,z] coordinates of each particle after relaxation.

short-name

typestring
has-unitfalse
extent[":"]
requiredfalse
descriptionShort name defining the cubic crystal type.

space-group

typestring
has-unitfalse
extent[]
requiredfalse
descriptionHermann-Mauguin designation for the space group associated with the symmetry of the crystal (e.g. Immm, Fm-3m, P6_3/mmc).

wyckoff-coordinates

typefloat
has-unitfalse
extent[":" 3]
requiredfalse
descriptionCoordinates 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

typestring
has-unitfalse
extent[":"]
requiredfalse
descriptionMultiplicity 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

typestring
has-unitfalse
extent[":"]
requiredfalse
descriptionThe 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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