spinw.genlattice method

generates crystal lattice

Syntax

genlattice(obj,Name,Value)

R = genlattice(___)

Description

genlattice(obj,Name,Value) generates all necessary parameters to define a lattice including space group symmetry and store the result it in the spinw.lattice field.

R = genlattice(___) also returns the rotation matrix that rotates the inpub basis vectors to the internal coordinate system.

Alternatively the lattice parameters can be given directly when the spinw object is created using the spinw(inpStr) command, where struct contains the fields with initial parameters, e.g.:

inpStr.lattice.lat_const = [3 3 4];

Example

crystal.genlattice('lat_const',[3 3 4],'angled',[90 90 120],'spgr','P 6')
crystal.genlattice('lat_const',[3 3 4],'angled',[90 90 120],'spgr',168)
crystal.genlattice('lat_const',[3 3 4],'angled',[90 90 120],'spgr','-y,x-y,z; -x,-y,z','label','R -3 m')

The three lines are equivalent, both will create hexagonal lattice, with $P6$ space group.

Input

obj: spinw object.

Options

angled

[α, β, γ] angles in °, dimensions are $[1\times 3]$ .

angle

[α, β, γ] angles in radian, dimensions are $[1\times 3]$ .

lat_const

[a, b, c] lattice parameters in units defined in spinw.unit (with Å being the default), dimensions are $[1\times 3]$ .

spgr

Defines the space group. Can have the following values:

space group label string, name of the space group, can be any label defined in the symmetry.dat file.
space group index line number in the symmetry.dat file.
space group operators matrix with dimensions $[3\times 4\times n_{op}]$ .

The symmetry.dat file stores definition of the 230 space groups in standard settings as it is in the International Tables of Crystallography. Additional lines can be added to the symmetry.dat file using the swsym.add function which later can be used in the spgr option.

If the spgr option is 0, no symmetry will be used. The spinw.gencoupling function will determine the equivalent bonds based on bond length.

label

Optional label for the space group if the generators are given in the spgr option. bv

Basis vectors given in a matrix with dimensions of $[3\times 3]$ , where each column defines a basis vector.

origin

Origin for the space group operators, default value is [0 0 0].

perm

Permutation of the abc axes of the space group operators.

nformula

Gives the number of formula units in the unit cell. It is used to normalize cross section in absolute units. Default value is 0, when cross section is normalized per unit cell.

Output

R

Rotation matrix that brings the input basis vector to the SpinW compatible form:

BVspinw = R*BV

The result of the spinw.genlattice function is that obj.lattice field will be changed based on the input, the lattice parameters are stored directly and the optional space group string is converted into space group operator matrices.