Coverage for gpaw/test/ext_potential/test_constant_e_field.py: 100%

1import pytest 

2import numpy as np 

3from ase import Atoms 

4from ase.units import Hartree, Bohr 

5 

6from gpaw import GPAW 

7from gpaw.external import ConstantElectricField 

8from gpaw.external import static_polarizability 

9 

10 

11@pytest.mark.old_gpaw_only 

12def test_ext_potential_constant_e_field(in_tmp_dir): 

13 """A proton in an electric field.""" 

14 h = Atoms('H') 

15 h.center(vacuum=2.5) 

16 h.calc = GPAW(mode='fd', 

17 external=ConstantElectricField(1.0), # 1 V / Ang 

18 charge=1, 

19 txt='h.txt') 

20 e = h.get_potential_energy() 

21 f1 = h.get_forces()[0, 2] 

22 h[0].z += 0.001 

23 de = h.get_potential_energy() - e 

24 f2 = -de / 0.001 

25 print(f1, f2) 

26 assert abs(f1 - 1) < 1e-4 

27 assert abs(f2 - 1) < 5e-3 

28 

29 # Check writing and reading: 

30 h.calc.write('h') 

31 vext = GPAW('h', txt=None).hamiltonian.vext 

32 assert abs(vext.field_v[2] - 1.0 * Bohr / Hartree) < 1e-13 

33 

34 

35@pytest.mark.old_gpaw_only 

36def test_polarizability(in_tmp_dir): 

37 H2 = Atoms('H2', positions=[(0, 0, 0), (0.7, 0, 0)]) 

38 H2.center(vacuum=2.5) 

39 H2.calc = GPAW(mode='fd', symmetry={'point_group': False}) 

40 

41 strength = 0.1 # V/Ang 

42 alpha_cc = static_polarizability(H2, strength) 

43 

44 # make sure no external potential is left over 

45 assert H2.calc.parameters.external is None 

46 

47 assert alpha_cc.shape == (3, 3) 

48 assert alpha_cc == pytest.approx( 

49 np.diag([6.48529231e-02, 4.61303856e-2, 4.61303856e-2])) 

50 

51 # displace positions and make sure that you can still 

52 # get the energy 

53 H2[1].position[0] -= 0.001 

54 H2.get_potential_energy()