def test_cgf_kinetic(self):
"""
Test kinetic integrals for contracted Gaussians
Tij = <cgf_i | -1/2 nabla^{2} | 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')
T = np.zeros((2, 2))
T[0, 0] = integrator.kinetic(cgfs[0], cgfs[0])
T[0, 1] = T[1, 0] = integrator.kinetic(cgfs[0], cgfs[1])
T[1, 1] = integrator.kinetic(cgfs[1], cgfs[1])
T11 = 0.7600315809249878
T12 = 0.2364544570446014
np.testing.assert_almost_equal(T[0, 0], T11, 4)
np.testing.assert_almost_equal(T[1, 1], T11, 4)
np.testing.assert_almost_equal(T[0, 1], T12, 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.kinetic(cgfs1[cgf_id1], cgfs1[cgf_id2])
cgfs2, nuclei = mol2.build_basis('sto3g')
right = integrator.kinetic(cgfs2[cgf_id1], cgfs2[cgf_id2])
return (right - left) / diff
