Coverage for gpaw/test/generic/test_bulk.py: 100%

1from ase import Atom, Atoms 

2from gpaw import GPAW 

3import pytest 

4import numpy as np 

5 

6 

7def test_generic_bulk(): 

8 bulk = Atoms([Atom('Li')], pbc=True) 

9 k = 4 

10 g = 8 

11 calc = GPAW(mode='fd', gpts=(g, g, g), kpts=(k, k, k), nbands=2) 

12 bulk.calc = calc 

13 a = np.linspace(2.6, 2.8, 5) 

14 e = [] 

15 for x in a: 

16 bulk.set_cell((x, x, x)) 

17 e1 = bulk.get_potential_energy() 

18 e.append(e1) 

19 

20 fit = np.polyfit(a, e, 2) 

21 a0 = np.roots(np.polyder(fit, 1))[0] 

22 e0 = np.polyval(fit, a0) 

23 print('a,e =', a0, e0) 

24 assert a0 == pytest.approx(2.641, abs=0.001) 

25 assert e0 == pytest.approx(-1.98357, abs=0.0002) 

26 

27 energy_tolerance = 0.0002 

28 assert e1 == pytest.approx(-1.96157, abs=energy_tolerance)