[Pw_forum] Meaning of "Total SCF correction"

[Stefano de Gironcoli]

Henning Glawe wrote:

>Moin,
>pw.x writes out a 'Total SCF correction' together with the total force.
>What is the meaning of this correction?
>  
>
 >>>>  from force_corr.f90

!-----------------------------------------------------------------------
subroutine force_corr (forcescc)
  !-----------------------------------------------------------------------
  !   This routine calculates the force term vanishing at full
  !     self-consistency. It follows the suggestion of Chan-Bohnen-Ho
  !     (PRB 47, 4771 (1993)). The true charge density is approximated
  !     by means of a free atom superposition.
  !     (alessio f.)
  ! Uses superposition of atomic charges contained in the array rho_at
  ! and already set in readin-readvan

 >>>>> from forces.f90

   DO na = 1, nat
      DO ipol = 1, 3
         sum = sum + force(ipol,na)**2
         sumscf = sumscf + forcescc(ipol,na)**2
      END DO
  END DO
  !
  WRITE( stdout, '(/5x,"Total force = ",F12.6,5X, &
              &  "Total SCF correction = ",F12.6)') SQRT( sum ), SQRT( 
sumscf )


stefano