def test_cgf_overlap(self):
"""
Test kinetic integrals for contracted Gaussians
Sij = <cgf_i | cgf_j>
"""
# construct integrator object
integrator = PyQInt()
# build hydrogen molecule
mol = Molecule("H2")
mol.add_atom('H', 0.0, 0.0, 0.0)
mol.add_atom('H', 0.0, 0.0, 1.4)
cgfs, nuclei = mol.build_basis('sto3g')
S = np.zeros((2, 2))
S[0, 0] = integrator.overlap(cgfs[0], cgfs[0])
S[0, 1] = S[1, 0] = integrator.overlap(cgfs[0], cgfs[1])
S[1, 1] = integrator.overlap(cgfs[1], cgfs[1])
S11 = 1.0
S12 = 0.65931845
np.testing.assert_almost_equal(S[0, 0], S11, 4)
np.testing.assert_almost_equal(S[1, 1], S11, 4)
np.testing.assert_almost_equal(S[0, 1], S12, 4)
def calculate_force_finite_difference(mol, nuc_id, cgf_id1, cgf_id2, coord):
# build integrator object
integrator = PyQInt()
# distance
diff = 0.00001
mol1 = deepcopy(mol)
mol1.atoms[nuc_id][1][coord] -= diff / 2
mol2 = deepcopy(mol)
mol2.atoms[nuc_id][1][coord] += diff / 2
# build hydrogen molecule
cgfs1, nuclei = mol1.build_basis('sto3g')
left = integrator.overlap(cgfs1[cgf_id1], cgfs1[cgf_id2])
cgfs2, nuclei = mol2.build_basis('sto3g')
right = integrator.overlap(cgfs2[cgf_id1], cgfs2[cgf_id2])
return (right - left) / diff
