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import pytest
import numpy as np
from ase import io
from ase.optimize import BFGS
from ase.build import bulk
calc = pytest.mark.calculator
@calc('vasp')
def test_vasp_Al_volrelax(factory):
"""
Run VASP tests to ensure that relaxation with the VASP calculator works.
This is conditional on the existence of the VASP_COMMAND or VASP_SCRIPT
environment variables.
"""
# -- Perform Volume relaxation within Vasp
def vasp_vol_relax():
Al = bulk('Al', 'fcc', a=4.5, cubic=True)
calc = factory.calc(xc='LDA',
isif=7,
nsw=5,
ibrion=1,
ediffg=-1e-3,
lwave=False,
lcharg=False)
Al.calc = calc
Al.get_potential_energy() # Execute
# Explicitly parse atomic position output file from Vasp
CONTCAR_Al = io.read('CONTCAR', format='vasp')
print('Stress after relaxation:\n', calc.read_stress())
print('Al cell post relaxation from calc:\n',
calc.get_atoms().get_cell())
print('Al cell post relaxation from atoms:\n', Al.get_cell())
print('Al cell post relaxation from CONTCAR:\n', CONTCAR_Al.get_cell())
# All the cells should be the same.
assert (calc.get_atoms().get_cell() == CONTCAR_Al.get_cell()).all()
assert (Al.get_cell() == CONTCAR_Al.get_cell()).all()
return Al
# -- Perform Volume relaxation using ASE with Vasp as force/stress calculator
def ase_vol_relax():
Al = bulk('Al', 'fcc', a=4.5, cubic=True)
calc = factory.calc(xc='LDA')
Al.calc = calc
from ase.constraints import StrainFilter
sf = StrainFilter(Al)
qn = BFGS(sf, logfile='relaxation.log')
qn.run(fmax=0.1, steps=5)
print('Stress:\n', calc.read_stress())
print('Al post ASE volume relaxation\n', calc.get_atoms().get_cell())
return Al
# Test function for comparing two cells
def cells_almost_equal(cellA, cellB, tol=0.01):
return (np.abs(cellA - cellB) < tol).all()
# Correct LDA relaxed cell
a_rel = 4.18
LDA_cell = np.diag([a_rel, a_rel, a_rel])
Al_vasp = vasp_vol_relax()
Al_ase = ase_vol_relax()
assert cells_almost_equal(LDA_cell, Al_vasp.get_cell())
assert cells_almost_equal(LDA_cell, Al_ase.get_cell())
# Cleanup
Al_ase.calc.clean()
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