Coverage for gpaw/test/parallel/test_diamond_gllb.py: 21%

1"""Calculate diamond with various parallelizations with GLLBSC.""" 

2import pytest 

3from gpaw.mpi import world 

4from ase.build import bulk 

5from gpaw import GPAW, Mixer 

6 

7 

8@pytest.mark.gllb 

9@pytest.mark.skipif(world.size < 4, 

10 reason='world.size < 4') 

11def test_parallel_diamond_gllb(in_tmp_dir): 

12 xc = 'GLLBSC' 

13 KS_gap_ref = 4.180237125868162 

14 QP_gap_ref = 5.469387490357182 

15 # M. Kuisma et. al, https://doi.org/10.1103/PhysRevB.82.115106 

16 # C: KS gap 4.14 eV, QP gap 5.41eV, expt. 5.48 eV 

17 KSb = [] 

18 dxcb = [] 

19 

20 eigensolver = 'rmm-diis' 

21 

22 for band in [1, 2, 4]: 

23 # Calculate ground state 

24 atoms = bulk('C', 'diamond', a=3.567) 

25 calc = GPAW(mode='fd', 

26 h=0.15, 

27 kpts=(4, 4, 4), 

28 xc=xc, 

29 nbands=8, 

30 mixer=Mixer(0.5, 5, 50.0), 

31 eigensolver=eigensolver, 

32 parallel={'band': band}) 

33 atoms.calc = calc 

34 atoms.get_potential_energy() 

35 

36 # Calculate accurate KS-band gap from band structure 

37 bs_calc = calc.fixed_density(kpts={'path': 'GX', 'npoints': 12}, 

38 symmetry='off', 

39 nbands=8, 

40 convergence={'bands': 8}, 

41 eigensolver=eigensolver) 

42 # Get the accurate KS-band gap 

43 homo, lumo = bs_calc.get_homo_lumo() 

44 

45 # Calculate the discontinuity potential with accurate band gap 

46 response = calc.hamiltonian.xc.response 

47 dxc_pot = response.calculate_discontinuity_potential(homo, lumo) 

48 

49 # Calculate the discontinuity using the band structure calculator 

50 bs_response = bs_calc.hamiltonian.xc.response 

51 KS_gap, dxc = bs_response.calculate_discontinuity(dxc_pot) 

52 assert KS_gap == pytest.approx(lumo - homo, abs=1e-10) 

53 assert KS_gap == pytest.approx(KS_gap_ref, abs=1e-4) 

54 

55 QP_gap = KS_gap + dxc 

56 assert QP_gap == pytest.approx(QP_gap_ref, abs=1e-4) 

57 KSb.append(KS_gap) 

58 dxcb.append(dxc) 

59 

60 assert abs(KSb[0] - KSb[1]) < 1e-6 

61 assert abs(KSb[0] - KSb[2]) < 1e-6 

62 assert abs(dxcb[0] - dxcb[1]) < 1e-6 

63 assert abs(dxcb[0] - dxcb[2]) < 1e-6