def test_mbd_coulomb():
a = 14.4
beta = 2.0
enes = []
for coords, species, vol_ratios in peptide_meoh:
geom = MBDGeom(coords, get_spectrum=True)
_, eigs, C = geom.mbd_energy_species(species, vol_ratios, beta=0.83)
omega_t = np.sqrt(eigs)
alpha_0, C6, R_vdw = from_volumes(species, vol_ratios)
omega = 4 * C6 / (3 * alpha_0 ** 2)
charges = np.ones_like(alpha_0)
masses = 1 / (alpha_0 * omega ** 2)
ecoul = geom.coulomb_energy(
charges, masses, omega_t, 'fermi', R_vdw, beta, a, C
)
edip = geom.dipole_energy(
alpha_0, omega, omega_t, 'fermi,dip', R_vdw, beta, a, C
)
C = np.identity(len(omega_t))
omega_non = np.repeat(omega, 3)
ecoul_non = geom.coulomb_energy(
charges, masses, omega_non, 'fermi', R_vdw, beta, a, C
)
edip_non = geom.dipole_energy(
alpha_0, omega, omega_t, 'fermi,dip', R_vdw, beta, a, C
)
enes.append(ecoul - edip - (ecoul_non - edip_non))
ene_int = enes[2] - enes[0] - enes[1]
assert ene_int == approx(0.0002460638172163822 / 627.503, rel=1e-10)
def test_argon_dimer_rsscs_rpa():
geom = MBDGeom([(0, 0, 0), (0, 0, 4 * ang)], do_rpa=True, get_rpa_orders=True)
ene, orders = geom.mbd_energy_species(['Ar', 'Ar'], [1, 1], 0.83)
assert ene == approx(-0.0002462647623815428, rel=1e-10)
assert orders[1] == approx(-0.0002461558113413099, rel=1e-10)
assert orders[2] == approx(0)
assert orders[3] == approx(-1.0885208380438466e-07, rel=1e-10)
def test_argon_crystal_modes():
coords, lattice, k_grid, species, vol_ratios = argon_crystal
geom = MBDGeom(
coords, lattice, custom_k_pts=[(0, 0, 0), (0.1, 0, 0)], get_spectrum=True
)
_, eigs, C = geom.mbd_energy_species(species, vol_ratios, 0.83)
assert abs(C[:, :, 0].imag).sum() == approx(0)
assert abs(C[:, :, 1].imag).sum() != approx(0)