"""
Helper functions for returning special geometries often encountered
"""
from __future__ import print_function, division
import numpy as np
from sisl import Atom, Geometry, SuperCell
__all__ = ['honeycomb', 'graphene']
[docs]def honeycomb(bond, atom, orthogonal=False):
"""
Returns a honeycomb geometry with the graphene unit-cell (2 atoms)
"""
sq3h = 3.**.5 * 0.5
if orthogonal:
sc = SuperCell(np.array([[3., 0., 0.],
[0., 2 * sq3h, 0.],
[0., 0., 10.]], np.float64) * bond, nsc=[3, 3, 1])
g = Geometry(np.array([[0., 0., 0.],
[0.5, sq3h, 0.],
[1.5, sq3h, 0.],
[2., 0., 0.]], np.float64) * bond,
atom, sc=sc)
else:
sc = SuperCell(np.array([[1.5, sq3h, 0.],
[1.5, -sq3h, 0.],
[0., 0., 10.]], np.float64) * bond, nsc=[3, 3, 1])
g = Geometry(np.array([[0., 0., 0.],
[1., 0., 0.]], np.float64) * bond,
atom, sc=sc)
return g
[docs]def graphene(bond=1.42, atom=None, orthogonal=False):
"""
Returns a geometry with the graphene unit-cell (2 atoms)
"""
if atom is None:
return honeycomb(bond, Atom(Z=6, R=bond * 1.01), orthogonal)
return honeycomb(bond, atom, orthogonal)