import numpy as np
from sisl._internal import set_module
from sisl import Atom, Geometry, SuperCell
__all__ = ['honeycomb', 'graphene']
@set_module("sisl.geom")
def honeycomb(bond, atoms, orthogonal=False):
""" Honeycomb lattice with 2 or 4 atoms per unit-cell, latter orthogonal cell
This enables creating BN lattices with ease, or graphene lattices.
Parameters
----------
bond : float
bond length between atoms (*not* lattice constant)
atoms : Atom
the atom (or atoms) that the honeycomb lattice consists of
orthogonal : bool, optional
if True returns an orthogonal lattice
See Also
--------
graphene: the equivalent of this, but with default of Carbon atoms
bilayer: create bilayer honeycomb lattices
"""
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,
atoms, 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,
atoms, sc=sc)
return g
[docs]def graphene(bond=1.42, atoms=None, orthogonal=False):
""" Graphene lattice with 2 or 4 atoms per unit-cell, latter orthogonal cell
Parameters
----------
bond : float
bond length between atoms (*not* lattice constant)
atom : Atom, optional
the atom (or atoms) that the honeycomb lattice consists of.
Default to Carbon atom.
orthogonal : bool, optional
if True returns an orthogonal lattice
See Also
--------
honeycomb: the equivalent of this, but with non-default atoms
bilayer: create bilayer honeycomb lattices
"""
if atoms is None:
return honeycomb(bond, Atom(Z=6, R=bond * 1.01), orthogonal)
return honeycomb(bond, atoms, orthogonal)