[Pw_forum] about the output of the epsilon.x

[Paolo Giannozzi]

On Fri, 2014-09-19 at 22:00 +0900, shuai wrote:

> To whom has experience with epsilon.x

not to me. Anyway, it took me 2' to follow "wmin" and "wmax" in code
PP/src/epsilon.f90: in subroutine "grid_build", you have

  ! set the energy grid
  !
  alpha = (wmax - wmin) / REAL(nw, DP)
  DO iw = 1, nw
      wgrid(iw) = wmin + iw * alpha
  ENDDO

which clearly shows that the first grid point is not wmin but
wmin + (wmax-wmin)/nw (nw being the number of grid points). I
guess this should be

  alpha = (wmax - wmin) / REAL(nw-1, kind=DP)
  DO iw = 1, nw
      wgrid(iw) = wmin + (iw-1) * alpha
  ENDDO

Paolo

> I calculated the dielectric tensor using epsilon.x and got the output 
> files described in the eps_man.pdf. the input is:
> 
>   &inputpp
>      outdir = '/'
>      prefix = 'Si'
>      calculation = 'eps'
>   /
>   &energy_grid
>      smeartype = 'gauss'
>      intersmear = 0.136d0
>      intrasmear = 0.0d0
>      wmax = 10
>      wmin = 0
>      nw = 200
>      shift = 0
>   /
> 
> 
> But in the output files the values of the frequency are from 0.005 to 10 
> with an increment of 0.005, in total 200 values in accordance with the 
> 'nw = 200'. My question is how to set for getting the results of 
> frequency= 0?
> 
> Thanks in advance.
> 
> Sincerely,
> 
> S. Zhao
> 

-- 
 Paolo Giannozzi, Dept. Chemistry&Physics&Environment, 
 Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
 Phone +39-0432-558216, fax +39-0432-558222