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def test_qmmm():
from math import cos, sin, pi
import numpy as np
import ase.units as units
from ase import Atoms
from ase.calculators.tip3p import TIP3P, epsilon0, sigma0, rOH, angleHOH
from ase.calculators.qmmm import (SimpleQMMM, EIQMMM, LJInteractions,
LJInteractionsGeneral)
from ase.constraints import FixInternals
from ase.optimize import GPMin
r = rOH
a = angleHOH * pi / 180
# From https://doi.org/10.1063/1.445869
eexp = 6.50 * units.kcal / units.mol
dexp = 2.74
aexp = 27
D = np.linspace(2.5, 3.5, 30)
i = LJInteractions({('O', 'O'): (epsilon0, sigma0)})
# General LJ interaction object
sigma_mm = np.array([0, 0, sigma0])
epsilon_mm = np.array([0, 0, epsilon0])
sigma_qm = np.array([0, 0, sigma0])
epsilon_qm = np.array([0, 0, epsilon0])
ig = LJInteractionsGeneral(sigma_qm, epsilon_qm, sigma_mm, epsilon_mm, 3)
for calc in [TIP3P(),
SimpleQMMM([0, 1, 2], TIP3P(), TIP3P(), TIP3P()),
SimpleQMMM([0, 1, 2], TIP3P(), TIP3P(), TIP3P(), vacuum=3.0),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), i),
EIQMMM([3, 4, 5], TIP3P(), TIP3P(), i, vacuum=3.0),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), i, vacuum=3.0),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), ig),
EIQMMM([3, 4, 5], TIP3P(), TIP3P(), ig, vacuum=3.0),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), ig, vacuum=3.0)]:
dimer = Atoms('H2OH2O',
[(r * cos(a), 0, r * sin(a)),
(r, 0, 0),
(0, 0, 0),
(r * cos(a / 2), r * sin(a / 2), 0),
(r * cos(a / 2), -r * sin(a / 2), 0),
(0, 0, 0)])
dimer.calc = calc
E = []
F = []
for d in D:
dimer.positions[3:, 0] += d - dimer.positions[5, 0]
E.append(dimer.get_potential_energy())
F.append(dimer.get_forces())
F = np.array(F)
F1 = np.polyval(np.polyder(np.polyfit(D, E, 7)), D)
F2 = F[:, :3, 0].sum(1)
error = abs(F1 - F2).max()
assert error < 0.01
dimer.constraints = FixInternals(
bonds=[(r, (0, 2)), (r, (1, 2)),
(r, (3, 5)), (r, (4, 5))],
angles_deg=[(np.degrees(a), (0, 2, 1)), (np.degrees(a), (3, 5, 4))])
opt = GPMin(dimer,
trajectory=calc.name + '.traj', logfile=calc.name + 'd.log')
opt.run(0.01)
e0 = dimer.get_potential_energy()
d0 = dimer.get_distance(2, 5)
R = dimer.positions
v1 = R[1] - R[5]
v2 = R[5] - (R[3] + R[4]) / 2
a0 = np.arccos(np.dot(v1, v2) /
(np.dot(v1, v1) * np.dot(v2, v2))**0.5) / np.pi * 180
fmt = '{0:>20}: {1:.3f} {2:.3f} {3:.3f} {4:.1f}'
print(fmt.format(calc.name, -min(E), -e0, d0, a0))
assert abs(e0 + eexp) < 0.002
assert abs(d0 - dexp) < 0.01
assert abs(a0 - aexp) < 4
print(fmt.format('reference', 9.999, eexp, dexp, aexp))
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