[ase-users] "RuntimeError: Could not find k+q!"

[Robert Campana]

Hello everybody,

I have been attempting to run  a script that can calculate the EELS spectra
for a silver slab.  As a base, I am trying to use the GPAW wiki EELS
calculation for graphite (
https://svn.fysik.dtu.dk/projects/gpaw/trunk/doc/tutorials/dielectric_response/graphite_EELS.py).


I have so far been unable to overcome the error "RuntimeError: Could not
find k+q!".  This error occurs somewhere around line 26 in the script at
the end of this message.  When the script is run, silverslab.gpw (line 24)
writes successfully.  However, silverslab_q_list is written but is blank.
Then the for loop beginning in line 27 begins iterating but only partially
generates out_df_1.txt (line 35) before stopping at that point.

I have no idea what is going on here.  I already spoke about this with
someone I know who has worked with GPAW quite a bit, and he cannot figure
it out.  So, I need to ask the highest source.  Do any of you have any
ideas about how to fix this error?  If you can offer any advice, I'd really
appreciate it!

Thanks so much,
Robert

1 from math import sqrt
2 import numpy as np
3 from ase import Atoms
4 from ase.units import Bohr
5 from ase.parallel import paropen
6 from gpaw import GPAW, FermiDirac
7 from gpaw.response.df import DF
8 from ase.lattice.surface import fcc111
9 from ase.lattice.surface import surface


10 # Part 1: Ground state calculation
11 atoms=fcc111(symbol='Ag',size[1,1,10],a=4.167,vacuum=10,orthogonal=False)
12 atoms.set_pbc([1,1,1])

13 calc = GPAW(xc='LDA',
14             kpts=(8,8,1),
15             h=0.2,
16             basis='dzp',
17             nbands=180,
18             convergence={'bands':175},
19             eigensolver='cg',
20             occupations=FermiDirac(0.05),
21             txt='out_gs.txt')

22 atoms.set_calculator(calc)
23 atoms.get_potential_energy()
24 calc.write('silverslab.gpw',mode='all')

25 # Part 2: Spectra calculations
26 f = paropen('silverslab_q_list', 'w')

27 for i in range(1,8):
28     df = DF(calc='silverslab.gpw',
29             nbands=175,
30             q=np.array([i/20., 0., 0.]),
31             #q=np.array([i/20., -i/20., 0.])
32             w=np.linspace(0, 40, 401),
33             eta=0.2,
34             ecut=40+(i-1)*10,
35             txt='out_df_%d.txt' %(i))

36     df.get_EELS_spectrum(filename='silverslab_EELS_%d' %(i))
37     df.check_sum_rule()         # Check f-sum rule.

38     print >> f, sqrt(np.inner(df.qq_v / Bohr, df.qq_v / Bohr))
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