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mirror of https://github.com/pfloos/quack synced 2024-12-24 21:33:45 +01:00
QuAcK/src/GW/static_screening_WD_pp.f90

134 lines
2.8 KiB
Fortran

subroutine static_screening_WD_pp(ispin,eta,nBas,nC,nO,nV,nR,nS,nOO,nVV,lambda,ERI,Omega,rho,WD)
! Compute the OOOO block of the static screening W for the pp-BSE
implicit none
include 'parameters.h'
! Input variables
integer,intent(in) :: ispin
integer,intent(in) :: nBas
integer,intent(in) :: nC
integer,intent(in) :: nO
integer,intent(in) :: nV
integer,intent(in) :: nR
integer,intent(in) :: nS
integer,intent(in) :: nOO
integer,intent(in) :: nVV
double precision,intent(in) :: eta
double precision,intent(in) :: lambda
double precision,intent(in) :: ERI(nBas,nBas,nBas,nBas)
double precision,intent(in) :: Omega(nS)
double precision,intent(in) :: rho(nBas,nBas,nS)
! Local variables
double precision,external :: Kronecker_delta
double precision :: chi
double precision :: eps
integer :: i,j,k,l,ij,kl,m
! Output variables
double precision,intent(out) :: WD(nOO,nOO)
! Initialization
WD(:,:) = 0d0
!---------------!
! Singlet block !
!---------------!
if(ispin == 1) then
ij = 0
do i=nC+1,nO
do j=i,nO
ij = ij + 1
kl = 0
do k=nC+1,nO
do l=k,nO
kl = kl + 1
chi = 0d0
do m=1,nS
eps = Omega(m)**2 + eta**2
chi = chi + rho(i,k,m)*rho(j,l,m)*Omega(m)/eps &
+ rho(i,l,m)*rho(j,k,m)*Omega(m)/eps
enddo
WD(ij,kl) = + 4d0*lambda*chi/sqrt((1d0 + Kronecker_delta(i,j))*(1d0 + Kronecker_delta(k,l)))
end do
end do
end do
end do
end if
!---------------!
! Triplet block !
!---------------!
if(ispin == 2) then
ij = 0
do i=nC+1,nO
do j=i+1,nO
ij = ij + 1
kl = 0
do k=nC+1,nO
do l=k+1,nO
kl = kl + 1
chi = 0d0
do m=1,nS
eps = Omega(m)**2 + eta**2
chi = chi + rho(i,k,m)*rho(j,l,m)*Omega(m)/eps &
- rho(i,l,m)*rho(j,k,m)*Omega(m)/eps
enddo
WD(ij,kl) = + 4d0*lambda*chi
end do
end do
end do
end do
end if
!---------------!
! SpinOrb block !
!---------------!
if(ispin == 4) then
ij = 0
do i=nC+1,nO
do j=i+1,nO
ij = ij + 1
kl = 0
do k=nC+1,nO
do l=k+1,nO
kl = kl + 1
chi = 0d0
do m=1,nS
eps = Omega(m)**2 + eta**2
chi = chi + rho(i,k,m)*rho(j,l,m)*Omega(m)/eps &
- rho(i,l,m)*rho(j,k,m)*Omega(m)/eps
enddo
WD(ij,kl) = + 2d0*lambda*chi
end do
end do
end do
end do
end if
end subroutine static_screening_WD_pp