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# fmt: off
import numpy as np
import pytest
from ase import Atoms
from ase.calculators.bond_polarizability import (
BondPolarizability,
Linearized,
LippincottStuttman,
)
def test_CC_bond():
"""Test polarizabilties of a single CC bond"""
C2 = Atoms('C2', positions=[[0, 0, 0], [0, 0, 1.69]])
def check_symmetry(alpha):
alpha_diag = np.diagonal(alpha)
assert alpha == pytest.approx(np.diag(alpha_diag))
assert alpha_diag[0] == alpha_diag[1]
bp = BondPolarizability()
check_symmetry(bp(C2))
bp = BondPolarizability(Linearized())
check_symmetry(bp(C2))
def test_symmetry():
for lin in [LippincottStuttman(), Linearized()]:
assert lin('B', 'N', 1) == lin('N', 'B', 1)
def test_2to3():
"""Compare polarizabilties of one and two bonds"""
Si2 = Atoms('Si2', positions=[[0, 0, 0], [0, 0, 2.5]])
Si3 = Atoms('Si3', positions=[[0, 0, -2.5], [0, 0, 0], [0, 0, 2.5]])
bp = BondPolarizability()
bp2 = bp(Si2)
# polarizability is a tensor
assert bp2.shape == (3, 3)
# check sum of equal bonds
assert bp(Si3) == pytest.approx(2 * bp2)
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