QuAcK/src/GT/GTeh_self_energy.f90

subroutine GTeh_self_energy(eta,nBas,nC,nO,nV,nR,nS,e,Om,rhoL,rhoR,EcGM,Sig,Z)

! Compute correlation part of the self-energy for GTeh and the renormalization factor

  implicit none
  include 'parameters.h'

! Input variables

  double precision,intent(in)   :: eta
  integer,intent(in)            :: nBas
  integer,intent(in)            :: nC
  integer,intent(in)            :: nO
  integer,intent(in)            :: nV
  integer,intent(in)            :: nR
  integer,intent(in)            :: nS
  double precision,intent(in)   :: e(nBas)
  double precision,intent(in)   :: Om(nS)
  double precision,intent(in)   :: rhoL(nBas,nBas,nS)
  double precision,intent(in)   :: rhoR(nBas,nBas,nS)

! Local variables

  integer                       :: i,j,a,b
  integer                       :: p,q,r
  integer                       :: m
  double precision              :: num,eps

! Output variables

  double precision,intent(out)  :: EcGM
  double precision,intent(out)  :: Sig(nBas,nBas)
  double precision,intent(out)  :: Z(nBas)

! Initialize 

  Sig(:,:) = 0d0
  Z(:)     = 0d0

!----------------!
! GW self-energy !
!----------------!

  ! Occupied part of the correlation self-energy

!$OMP PARALLEL &
!$OMP SHARED(Sig,rho,eta,nS,nC,nO,nBas,nR,e,Om) &
!$OMP PRIVATE(m,i,q,p,num,eps) &
!$OMP DEFAULT(NONE)
!$OMP DO
  do q=nC+1,nBas-nR
     do p=nC+1,nBas-nR
        do m=1,nS
           do i=nC+1,nO

              eps = e(p) - e(i) + Om(m)
              num = rhoL(i,p,m)*rhoR(i,q,m)
              Sig(p,q) = Sig(p,q) + num*eps/(eps**2 + eta**2)
              if(p == q) Z(p) = Z(p) - num*(eps**2 - eta**2)/(eps**2 + eta**2)**2

           end do
        end do
     end do
  end do
!$OMP END DO
!$OMP END PARALLEL

    ! Virtual part of the correlation self-energy

!$OMP PARALLEL &
!$OMP SHARED(Sig,rho,eta,nS,nC,nO,nBas,nR,e,Om) &
!$OMP PRIVATE(m,a,q,p,num,eps) &
!$OMP DEFAULT(NONE)
!$OMP DO  
  do q=nC+1,nBas-nR
     do p=nC+1,nBas-nR
        do m=1,nS
           do a=nO+1,nBas-nR

              eps = e(p) - e(a) - Om(m)
              num = rhoL(p,a,m)*rhoR(q,a,m)
              Sig(p,q) = Sig(p,q) + num*eps/(eps**2 + eta**2)
              if(p == q) Z(p) = Z(p) - num*(eps**2 - eta**2)/(eps**2 + eta**2)**2

           end do
        end do
     end do
  end do
!$OMP END DO
!$OMP END PARALLEL

  ! Galitskii-Migdal correlation energy

  EcGM = 0d0
  do m=1,nS
    do a=nO+1,nBas-nR
      do i=nC+1,nO
        eps = e(a) - e(i) + Om(m)
        num = rhoL(i,a,m)*rhoR(i,a,m)
        EcGM = EcGM - num*eps/(eps**2 + eta**2)
      end do
    end do
  end do

! Compute renormalization factor from derivative 

  Z(:) = 1d0/(1d0 - Z(:))

end subroutine