def calculate_force_finite_difference(cgf1, cgf2, nucleus, charge, coord):
# build integrator object
integrator = PyQInt()
# distance
diff = 0.00001
# build hydrogen molecule
nucleus[coord] -= diff / 2.0
left = integrator.nuclear(cgf1, cgf2, nucleus, charge)
nucleus[coord] += diff
right = integrator.nuclear(cgf1, cgf2, nucleus, charge)
return (right - left) / diff
def test_cgf_nuclear(self):
"""
Test nuclear attraction integrals for contracted Gaussians
V^{(c)}_ij = <cgf_i | -Zc / |r-Rc| | cgf_j>
"""
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')
V1 = np.zeros((2,2))
V1[0,0] = integrator.nuclear(cgfs[0], cgfs[0], cgfs[0].p, 1)
V1[0,1] = V1[1,0] = integrator.nuclear(cgfs[0], cgfs[1], cgfs[0].p, 1)
V1[1,1] = integrator.nuclear(cgfs[1], cgfs[1], cgfs[0].p, 1)
V2 = np.zeros((2,2))
V2[0,0] = integrator.nuclear(cgfs[0], cgfs[0], cgfs[1].p, 1)
V2[0,1] = V2[1,0] = integrator.nuclear(cgfs[0], cgfs[1], cgfs[1].p, 1)
V2[1,1] = integrator.nuclear(cgfs[1], cgfs[1], cgfs[1].p, 1)
V11 = -1.2266135215759277
V12 = -0.5974172949790955
V22 = -0.6538270711898804
np.testing.assert_almost_equal(V1[0,0], V11, 4)
np.testing.assert_almost_equal(V1[1,1], V22, 4)
np.testing.assert_almost_equal(V1[0,1], V12, 4)
np.testing.assert_almost_equal(V2[0,0], V22, 4)
np.testing.assert_almost_equal(V2[1,1], V11, 4)
np.testing.assert_almost_equal(V2[0,1], V12, 4)