[Pw_forum] nscf+lelfield -----> Wrong k-string? Error

[Mojtaba Mirseraji]

Dear Users

I perform lelfield=.true. option in PWSCF (only in nscf) for berry
calculations of polarization but unfortunately
" Wrong k-string? "
error is showed.

I do not know how to solve it
I have this error when I run this nscf input:

 &CONTROL
 calculation = 'nscf' ,
 restart_mode = 'from_scratch' ,
 prefix= 'E',
 tstress = .true. ,
 tprnfor = .true. ,
 outdir='?',
 etot_conv_thr = 1.0E-6  ,
 forc_conv_thr = 1.0D-6 ,
 pseudo_dir = '?',
 lelfield= .true. ,
 lberry= .true. ,
 gdir= 3 ,
 nppstr= 25 ,
/
 &SYSTEM
ibrav = 0,
  celldm(1)= ?,
   nat = 5,
   ntyp = 3,
ecutwfc = 80.0 ,
ecutrho = 800.0 ,
  occupations = 'fixed' ,
/
 &ELECTRONS
  conv_thr = 1.D-6 ,
  diago_full_acc = .TRUE.,
  efield_cart(1) = 0.0D0 ,
  efield_cart(2) = 0.0D0 ,
  efield_cart(3) = 0.1D0 ,
/
ATOMIC_SPECIES
O 15.9994  ?.UPF
Ti47.867  ?.UPF
Ba137.327?.UPF
CELL_PARAMETERS {cubic}
1. 0.0.000
0. 1.0.000
0. 0.1.0135088
ATOMIC_POSITIONS {alat}
O0.0   0.5   0.497977245
O0.5   0.0   0.497977245
O0.5   0.5  -0.016512609
Ti   0.5   0.5   0.525300320
Ba   0.0   0.0   0.005257800
K_POINTS {automatic}
8  8  8   1   1   1



I have changed all numbers of this input file but this error appeared !

Regards

Mojtaba Mirseraji
Ph.D. Candidate
Theoretical Condensed Matter Physics
Arak Univ.
IRAN
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Re: [Pw_forum] nscf+lelfield -----> Wrong k-string? Error

[Mostafa Youssef]

Dear Mojtaba,

I have not encountered this error before, so I cannot comment on it.

But I think it is a little bit strange to apply the electric field in the nscf 
calculation only.  If you would like to calculate the polarization in the 
presence of the electric field , you need 2 scf calculations. The first at zero 
field but still with lelfield=.true., the second starts from the wave functions 
generated from the first but has the magnitude of the field you would like to 
apply.  Please see example 10 in PW/examples.



Mostafa Youssef
MIT
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