1import pytest
2from ase.spacegroup import crystal
3from ase.data import atomic_numbers, atomic_masses
4from ase.optimize import QuasiNewton
5from ase.constraints import UnitCellFilter
6from numpy.testing import assert_allclose
7
8
9@pytest.mark.calculator_lite
10@pytest.mark.calculator('lammpsrun')
11def test_NaCl_minimize(factory):
12    a = 6.15
13    n = 4
14    nacl = crystal(['Na', 'Cl'], [(0, 0, 0), (0.5, 0.5, 0.5)], spacegroup=225,
15                   cellpar=[a, a, a, 90, 90, 90]).repeat((n, n, n))
16
17    # Buckingham parameters from
18    # https://physics.stackexchange.com/questions/250018
19
20    pair_style = 'buck/coul/long 12.0'
21    pair_coeff = ['1 1 3796.9 0.2603 124.90']
22    pair_coeff += ['2 2 1227.2 0.3214 124.90']
23    pair_coeff += ['1 2 4117.9 0.3048 0.0']
24    masses = ['1 {}'.format(atomic_masses[atomic_numbers['Na']]),
25              '2 {}'.format(atomic_masses[atomic_numbers['Cl']])]
26
27    with factory.calc(
28            specorder=['Na', 'Cl'],
29            pair_style=pair_style,
30            pair_coeff=pair_coeff,
31            masses=masses,
32            atom_style='charge',
33            kspace_style='pppm 1.0e-5',
34            keep_tmp_files=True,
35    ) as calc:
36
37        for a in nacl:
38            if a.symbol == 'Na':
39                a.charge = +1.
40            else:
41                a.charge = -1.
42
43        nacl.calc = calc
44
45        assert_allclose(nacl.get_potential_energy(), -1896.216737561538,
46                        atol=1e-4, rtol=1e-4)
47
48        nacl.get_potential_energy()
49
50        ucf = UnitCellFilter(nacl)
51        with QuasiNewton(ucf, force_consistent=False) as dyn:
52            dyn.run(fmax=1.0E-2)
53
54        assert_allclose(nacl.get_potential_energy(), -1897.208861729178,
55                        atol=1e-4, rtol=1e-4)
56