[Pw_forum] problems calculating large numbers of empty states

[Brad Malone]

Hi, I'm trying to calculate a large number of conduction band states for
cubic Si (to be used in a subsequent GW calculation). However, when doing
this I sometimes run into errors like "problems computing cholesky
decomposition"  or "too many bands are unconverged". An example file of the
nscf calculation that generates an error for me is below:

The problems can sometimes be avoided by going to a larger wavefunction
cutoff, but I'm not sure if this is for good reason or if changing the
wavefunction cutoff just happens to avoid the error in the cases I've
tried.  Also, for a chosen grid (not the one listed below) I get errors when
trying to calculate 400,500, and 700 total bands, but the calculation works
fine for 600 bands.

Any insight to why this might happen or suggestions as to how to avoid it?

Thanks,
Brad Malone
UC Berkeley

-------------------------------------------------------------
&control
   prefix = 'si'
   calculation = 'nscf'
   restart_mode = 'from_scratch'
   wf_collect = .true.
   tstress = .false.
   tprnfor = .false.
   outdir = './'
   wfcdir = './'
   pseudo_dir = './'
/
&system
   ibrav = 0
   celldm(1) = 10.2612
   nat = 2
   ntyp = 1
   nbnd = 300
   ecutwfc = 40.0
/
&electrons
   conv_thr = 1.0d-10
   diagonalization = 'cg'
   diago_full_acc = .true.
/
CELL_PARAMETERS cubic
      +0.000000000  +0.500000000  +0.500000000
      +0.500000000  +0.000000000  +0.500000000
      +0.500000000  +0.500000000  +0.000000000
ATOMIC_SPECIES
  Si  28.086  Si.UPF
ATOMIC_POSITIONS crystal
  Si  -0.125000000  -0.125000000  -0.125000000
  Si  +0.125000000  +0.125000000  +0.125000000
K_POINTS crystal
   8
  0.000000000  0.000000000  0.000000000  1.0
  0.000000000  0.000000000  0.250000000  8.0
  0.000000000  0.000000000  0.500000000  4.0
  0.000000000  0.250000000  0.250000000  6.0
  0.000000000  0.250000000  0.500000000 24.0
  0.000000000  0.250000000  0.750000000 12.0
  0.000000000  0.500000000  0.500000000  3.0
  0.250000000  0.500000000  0.750000000  6.0
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