[Pw_forum] eps calculation error

Thu Apr 27 23:10:58 CEST 2017

the error comes from the code lines
————
  !
  ! check on k point weights, no symmetry operations are allowed
  !
  DO ik = 2, nks
     !
     IF ( abs( wk(1) - wk(ik) ) > 1.0d-8 ) &
        CALL errore('grid_build','non unifrom kpt grid', ik )
     !
  ENDDO
————

The code finds different k-points with different weight, understanding that you do non have an
explicit uniform k-point grid, whereas the (initially uniform) k-point grid has been reduced by pw.x
using symmetry.

It is advisable to carefully look at the provided documentation (and possibly, additional
information available on the web trough google searches), before executing a calculation.

Under PP/Doc there is a quite explanatory eps_man.pdf user guide to epsilon.x, where at the beginning
it is EXPLICITLY stated that:
"Epsilon.x doesn't support the reduction of the k-points grid into the unreducible Brillouin zone, so the previous PW runs must be
performed with a uniform k-points grid and all k-points weights must be equal to each other, i.e. in the k-points card the k-points
coordinates must be given manually in \emph{crystal} or \emph{alat} or \emph{bohr}, but not with the \emph{automatic} option. Also the
auto-symmetrization of k-points grid can produce a non uniform distribution of k-points weights, in order to avoid this
PW's behavior the variable NOSYM must be set .TRUE. disabling auto-symmetrization.”

So you must to manually specify ALL k points belonging to a uniform grid and additionally set nosym=.true. in the nscf calculation,
in order to avoid auto-symmetrisation issues.

Giovanni

> On 27 Apr 2017, at 17:01, Pinank Jariwala <pinankjariwala at gmail.com> wrote:
> 
> Sir, If I remove nosym and noinv then it gives error like below, so I put those two
> 
> Input file
> &inputpp
> outdir='./out/'
> prefix='SiH'
> calculation='eps'
> /
> &energy_grid
> smeartype='gauss'
> intersmear=0.136d0
> intrasmear=0.0d0
> wmax=20.0d0
> wmin=0.0d0
> nw=200
> shift=0.0d0
> nosym = .TRUE.
> noinv = .TRUE.
> /
> 
> output file
>      Reading input file...
> 
>  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>      Error in routine epsilon (19):
>      non unifrom kpt grid
> 
>  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> 
>      stopping ...
> 
> 
> On Thu, Apr 27, 2017 at 6:10 PM, Giovanni Cantele <giovanni.cantele at spin.cnr.it <mailto:giovanni.cantele at spin.cnr.it>> wrote:
> From PP/src/epsilon.f90:
> 
>   NAMELIST / inputpp / prefix, outdir, calculation
>   NAMELIST / energy_grid / smeartype, intersmear, intrasmear, nw, wmax, wmin, &
>                            nbndmin, nbndmax, shift
> 
> It seems to me that variables nosym and noinv are not allowed in namelist energy_grid
> 
> Giovanni
> 
>> On 27 Apr 2017, at 14:29, Pinank Jariwala <pinankjariwala at gmail.com <mailto:pinankjariwala at gmail.com>> wrote:
>> 
>> Dear qe users, 
>> I want to use epsilon.x to calculate optical property, but it shows error like below.
>> My system has 40 atoms.
>> 
>> Input file
>> &inputpp
>> outdir='./out/'
>> prefix='SiH'
>> calculation='eps'
>> /
>> &energy_grid
>> smeartype='gauss'
>> intersmear=0.136d0
>> intrasmear=0.0d0
>> wmax=20.0d0
>> wmin=0.0d0
>> nw=200
>> shift=0.0d0
>> nosym = .TRUE.
>> noinv = .TRUE.
>> /
>> 
>> output file
>>      Program epsilon v.5.2.0 starts on 22Apr2017 at 14:31:18 
>> 
>>      This program is part of the open-source Quantum ESPRESSO suite
>>      for quantum simulation of materials; please cite
>>          "P. Giannozzi et al., J. Phys.:Condens. Matter 21 395502 (2009);
>>           URL http://www.quantum-espresso.org <http://www.quantum-espresso.org/>", 
>>      in publications or presentations arising from this work. More details at
>>      http://www.quantum-espresso.org/quote <http://www.quantum-espresso.org/quote>
>> 
>>      Parallel version (MPI), running on    16 processors
>>      R & G space division:  proc/nbgrp/npool/nimage =      16
>> 
>> 
>>      Reading input file...
>> 
>>  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>>      Error in routine epsilon (19):
>>      reading namelist ENERGY_GRID
>>  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>> 
>>      stopping ...
>> 
>> -- 
>> Thanks & Regard
>>  
>> Jariwala P. H.
>> Research Scholar,
>> Department of Physics ,
>> V. N. S. G. University
>> e-mail :  pinankjariwala at gmail.com <mailto:pinankjariwala at gmail.com>
>> _______________________________________________
>> Pw_forum mailing list
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>> http://pwscf.org/mailman/listinfo/pw_forum <http://pwscf.org/mailman/listinfo/pw_forum>
> -- 
> 
> Giovanni Cantele, PhD
> CNR-SPIN
> c/o Dipartimento di Fisica
> Universita' di Napoli "Federico II"
> Complesso Universitario M. S. Angelo - Ed. 6
> Via Cintia, I-80126, Napoli, Italy
> e-mail: giovanni.cantele at spin.cnr.it <mailto:giovanni.cantele at spin.cnr.it>
> Phone: +39 081 676910
> Skype contact: giocan74
> 
> ResearcherID: http://www.researcherid.com/rid/A-1951-2009 <http://www.researcherid.com/rid/A-1951-2009>
> Web page: http://people.fisica.unina.it/~cantele <http://people.fisica.unina.it/~cantele>
> 
> 
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> 
> 
> 
> -- 
> Thanks & Regard
>  
> Jariwala Pinank H.
> Research Scholar,
> Department of Physics ,
> Veer Narmad South Gujarat University
> Surat-395 007 (Gujarat)
> India.
> e-mail :  pinankjariwala at gmail.com <mailto:pinankjariwala at gmail.com>
> Mo. No: +91-9979579050
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