[gpaw-users] Symmetry?

[Jens Jørgen Mortensen]

Den 31-10-2013 07:29, Robert Warmbier skrev:
> Dear GPAW users and developers,
>
> I was doing some calculations on a-quartz and was suprised to find, 
> that the reduced k-point set of gpaw was rather large. Apparently gpaw 
> found only 2 symmetries to exploit, while vasp found 6, for exactly 
> the same geometry.
>
> Is there a limitiation in gpaw or is my input wrong?

What kind of symmetries are missing?  Could it be that they are of the 
non-symmorphic type?  GPAW doesn't have those.

Jens Jørgen

> Thanks Robert
>
> here the input file:
>
> from ase import Atoms
> from gpaw import PW
> from gpaw import GPAW, FermiDirac
> import numpy as np
>
> name = 'SiO2 a-quartz'
>
> alat = 5.0324636616928924
> clat = 5.5210687420867108
>
> posSi1 = 0.4778762817077312
>
> a1 = alat*np.array([1.0, 0.0, 0.0])
> a2 = alat*np.array([-0.5, np.sqrt(3)/2, 0.0])
> a3 = clat*np.array([0.0, 0.0, 1.0])
>
> cell = np.array([a1,a2,a3])
>
> symbols = ['Si', 'Si', 'Si', 'O','O', 'O', 'O', 'O', 'O']
>
> crystal_positions = 
> [(posSi1,0.0,1./3.),(0.0,posSi1,2./3.),(1-posSi1,1-posSi1,0.0),
>                      (0.4153075517143993,  0.2531339614388382, 
> 0.2029892890232297),
>                      (0.7468660385611690,  0.1621735892755646, 
> 0.5363226470232412),
>                      (0.8378264107244283,  0.5846924482855935, 
> 0.8696559600232383),
>                      (0.2531339614388382,  0.4153075517143993, 
> 0.7970107259767609),
>                      (0.1621735892755646,  0.7468660385611690, 
> 0.4636773829767684),
>                      (0.5846924482855935,  0.8378264107244283, 
> 0.1303440469767658),
>                     ]
> atoms = Atoms(symbols=symbols,
>               scaled_positions=crystal_positions,
>               cell=cell,
>               pbc = True
>               )
>
> # first GS calc
> calc = GPAW(mode=PW(ecut=700,cell=cell),
>             xc='PBE',
>             kpts=(5,5,5),
>          #   txt='gs_e700_k5.out',
>         #    occupations=FermiDirac(0.05)
>             )
>
> atoms.set_calculator(calc)
> # Calculate the ground state
> energy = atoms.get_potential_energy()
> eigenvalues = calc.get_eigenvalues()
> print eigenvalues
>
> # Save the ground state
> calc.write('gs_e700_k5.gpw', 'all')
>
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