import numpy as np
[docs]class Cosine(object):
"""Cosine cutoff function
Parameters
----------
cutoff : float
The cutoff radius.
"""
def __init__(self, cutoff):
self.cutoff = cutoff
def __call__(self, rij):
"""Function to calculate Cosine cutoff function value
Parameters
----------
rij : float
Distance between two atoms.
Returns
-------
cutofffxn : float
Value of the cutoff function.
"""
if rij > self.cutoff:
cutofffxn = 0.0
else:
cutofffxn = 0.5 * (np.cos(np.pi * rij / self.cutoff) + 1.0)
return cutofffxn