Magnetic spin DoF

Simple cubic with non-collinear magnetic spin DoF and spin-orbit coupling

This example constructs the prim for simple cubic crystal system with non-collinear magnetic spin degrees of freedom (DoF) and spin-orbit coupling.

To construct this prim, the following must be specified:

• the lattice vectors

• basis site coordinates

• occupant DoF

• magnetic spin DoF

This example uses a fixed “A” sublattice for occ_dof, which by default are created as isotropic atoms.

import numpy as np
import libcasm.xtal as xtal

# Lattice vectors
lattice_column_vector_matrix = np.array([
    [1., 0., 0.],  # a
    [0., 1., 0.],  # a
    [0., 0., 1.],  # a
]).transpose()  # <--- note transpose
lattice = xtal.Lattice(lattice_column_vector_matrix)

# Basis sites positions, as columns of a matrix,
# in fractional coordinates with respect to the lattice vectors
coordinate_frac = np.array([
    [0., 0., 0.],  # coordinates of basis site, b=0
]).transpose()

# Occupation degrees of freedom (DoF)
occ_dof = [
    ["A"],  # occupants allowed on basis site, b=0
]

# Local continuous degrees of freedom (DoF)
# non-collinear magnetic spin DoF, with spin-orbit coupling
SOmagspin_dof = xtal.DoFSetBasis("SOmagspin")
local_dof = [
    [SOmagspin_dof],  # allow magnetic spin on basis site b=0
]

# Construct the prim
prim = xtal.Prim(lattice=lattice,
                 coordinate_frac=coordinate_frac,
                 occ_dof=occ_dof,
                 local_dof=local_dof,
                 title="simple_cubic_SOmagspin")

This prim as JSON: simple_cubic_SOmagspin.json