[Pw_forum] about electric field potential in pp.x

[xywu]

Dear all,

 I add a sawlike electric potential in SCF and want to get the electric 
potential from pp.x.
But when i use the pp.x with plot_num=12, the electric field potential 
in output file is zero.

But if i get the electric potential from pp.x without adding electric 
field in SCF, the error occurs as follows;

 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     from punch_plot : error #        -1
     e_field is not calculated
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
what's the wrong with it.

Please give me some advice.

! plot_num    selects what is saved in filplot:
  !                0=charge
  !                1=total potential V_bare+V_H + V_xc
  !                2=local ionic potential
  !                3=local density of states at e_fermi
  !                4=local density of electronic entropy
  !                5=STM images
  !                6=spin polarization (rho(up)-rho(down))
  !                7=|psi|^2
  !                8=electron localization function (ELF)
  !                9=planar average of all |psi|^2
  !               10=integrated local density of states (ILDOS) from
  !                  emin to emax (emin, emax in eV)
  !                  if emax is not specified, emax=E_fermi
  !               11=the V_bare + V_H potential
  !               12=the electric field potential
  !               13=the noncolinear magnetization.

BTW, still another question about add_efield.

In the file add_efield.f90

" !--------------------------------------------------------------------------
  subroutine add_efield(rho,vpoten,etotefield)
!--------------------------------------------------------------------------
!
!   This routine adds an electric field to the local potential. The
!   field is made artificially periodic by introducing a saw-tooth
!   potential. The field is parallel to a reciprocal lattice vector bg, 
!   according to the index edir.
!
!   if dipfield is false the electric field correction is added to the
!   potential given as input (the bare local potential) only
!   at the first call to this routine. In the following calls
!   the routine exit.
!
!   if dipfield is true the dipole moment per unit surface is calculated
!   and used to cancel the electric field due to periodic boundary
!   conditions. This potential is added to the Hartree and xc potential
!   in v_of_rho. NB: in this case the electric field contribution to the 
!   band energy is subtracted by deband.
"
"  if (first) then
     WRITE( stdout,*)
     WRITE( stdout,'(5x,"Adding an external electric field")')
     WRITE( stdout,'(5x,"Intensity [a.u.]: ",f15.8)') eamp
  endif
  if (dipfield) WRITE( stdout,'(5x,"Dipole field [a.u.]: ", f15.8)') dip
  if (first) then
     WRITE( stdout,'(5x,"Potential amplitude [Ry]: ", f15.8)') vamp
     WRITE( stdout,'(5x,"Total length [points]: ", i5)') npoints
     WRITE( stdout,'(5x,"Total length [bohr rad]: ", f15.8)') length
     WRITE( stdout,'(5x,"Field is reversed between points: ",2i6)')nmax, nmax+ndesc
  endif
"

And in a typical output file of PW.x with efield:
"
     Adding an external electric field
     Intensity [a.u.]:      0.01000000
     Potential amplitude [Ry]:      0.24480000
     Total length [points]:   200
     Total length [bohr rad]:     61.20000000
     Field is reversed between points:      1   161

"