import catkit
import numpy as np
import ase.build
import ase
[docs]def bulk(name, crystalstructure=None, primitive=False, **kwargs):
"""Return the standard conventional cell of a bulk structure
created using ASE. Accepts all keyword arguments for the ase
bulk generator.
Parameters
----------
name : Atoms object | str
Chemical symbol or symbols as in 'MgO' or 'NaCl'.
crystalstructure : str
Must be one of sc, fcc, bcc, hcp, diamond, zincblende,
rocksalt, cesiumchloride, fluorite or wurtzite.
primitive : bool
Return the primitive unit cell instead of the conventional
standard cell.
Returns
-------
standardized_bulk : Gratoms object
The conventional standard or primitive bulk structure.
"""
if isinstance(name, str):
atoms = ase.build.bulk(name, crystalstructure, **kwargs)
else:
atoms = name
standardized_bulk = catkit.gen.symmetry.get_standardized_cell(
atoms, primitive=primitive)
return standardized_bulk
[docs]def surface(
elements,
size,
miller=(1, 1, 1),
termination=0,
fixed=0,
vacuum=10,
orthogonal=False,
**kwargs):
"""A helper function to return the surface associated with a
given set of input parameters to the general surface generator.
Parameters
----------
elements : str or object
The atomic symbol to be passed to the as bulk builder function
or an atoms object representing the bulk structure to use.
size : list (3,)
Number of time to expand the x, y, and z primitive cell.
miller : list (3,) or (4,)
The miller index to cleave the surface structure from. If 4 values
are used, assume Miller-Bravis convention.
termination : int
The index associated with a specific slab termination.
fixed : int
Number of layers to constrain.
vacuum : float
Angstroms of vacuum to add to the unit cell.
orthogonal : bool
Force the slab generator to produce the most orthogonal slab.
Returns
-------
slab : Gratoms object
Return a slab generated from the specified bulk structure.
"""
if isinstance(elements, ase.Atoms):
atoms = elements
else:
bkwargs = kwargs.copy()
keys = ['crystalstructure', 'a', 'c', 'covera',
'u', 'orthorhombic', 'cubic']
for key in kwargs:
if key not in keys:
del bkwargs[key]
atoms = ase.build.bulk(elements, **bkwargs)
generator = catkit.gen.surface.SlabGenerator(
bulk=atoms,
miller_index=miller,
layers=size[-1],
vacuum=vacuum,
fixed=fixed,
layer_type=kwargs.get('layer_type', 'trim'),
attach_graph=kwargs.get('attach_graph', True),
standardize_bulk=kwargs.get('standardize_bulk', True),
tol=kwargs.get('tol', 1e-8)
)
if len(size) == 2:
size = size[0]
elif len(size) == 3 and not orthogonal:
size = size[:2]
if orthogonal:
catkit.gen.defaults['orthogonal'] = True
if isinstance(size, (list, tuple)):
size = np.prod(size[:2])
slab = generator.get_slab(size=size, iterm=termination)
return slab
[docs]def molecule(species, bond_index=None, vacuum=0):
"""Return list of enumerated gas-phase molecule structures based
on species and topology.
Parameters
----------
species : str
The chemical symbols to construct a molecule from.
bond_index : int
Construct the molecule as though it were adsorbed to a surface
parallel to the z-axis. Will bond by the atom index given.
vacuum : float
Angstroms of vacuum to pad the molecules with.
Returns
-------
images : list of Gratoms objects
3D structures of the requested chemical species and topologies.
"""
molecule_graphs = catkit.gen.molecules.get_topologies(species)
images = []
for atoms in molecule_graphs:
atoms = catkit.gen.molecules.get_3D_positions(atoms, bond_index)
atoms.center(vacuum)
images += [atoms]
return images