mirror of https://github.com/pfloos/quack
101 lines
2.2 KiB
Fortran
101 lines
2.2 KiB
Fortran
subroutine static_screening_WB_pp(ispin,eta,nBas,nC,nO,nV,nR,nS,nOO,nVV,lambda,ERI,Omega,rho,WB)
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! Compute the VVOO block of the static screening W for the pp-BSE
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implicit none
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include 'parameters.h'
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! Input variables
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integer,intent(in) :: ispin
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integer,intent(in) :: nBas
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integer,intent(in) :: nC
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integer,intent(in) :: nO
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integer,intent(in) :: nV
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integer,intent(in) :: nR
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integer,intent(in) :: nS
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integer,intent(in) :: nOO
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integer,intent(in) :: nVV
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double precision,intent(in) :: eta
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double precision,intent(in) :: lambda
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double precision,intent(in) :: ERI(nBas,nBas,nBas,nBas)
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double precision,intent(in) :: Omega(nS)
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double precision,intent(in) :: rho(nBas,nBas,nS)
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! Local variables
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double precision,external :: Kronecker_delta
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double precision :: chi
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double precision :: eps
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integer :: a,b,i,j,ab,ij,m
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! Output variables
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double precision,intent(out) :: WB(nVV,nOO)
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! Initialization
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WB(:,:) = 0d0
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!---------------!
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! Singlet block !
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!---------------!
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if(ispin == 1) then
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ab = 0
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do a=nO+1,nBas-nR
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do b=a,nBas-nR
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ab = ab + 1
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ij = 0
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do i=nC+1,nO
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do j=i,nO
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ij = ij + 1
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chi = 0d0
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do m=1,nS
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eps = Omega(m)**2 + eta**2
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chi = chi + rho(a,j,m)*rho(b,i,m)*Omega(m)/eps
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enddo
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WB(ab,ij) = WB(ab,ij) + 4d0*lambda*chi/sqrt((1d0 + Kronecker_delta(a,b))*(1d0 + Kronecker_delta(i,j)))
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end do
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end do
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end do
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end do
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end if
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!---------------!
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! Triplet block !
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!---------------!
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if(ispin == 2) then
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ab = 0
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do a=nO+1,nBas-nR
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do b=a+1,nBas-nR
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ab = ab + 1
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ij = 0
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do i=nC+1,nO
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do j=i+1,nO
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ij = ij + 1
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chi = 0d0
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do m=1,nS
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eps = Omega(m)**2 + eta**2
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chi = chi + rho(a,j,m)*rho(b,i,m)*Omega(m)/eps
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enddo
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WB(ab,ij) = WB(ab,ij) - 4d0*lambda*chi
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end do
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end do
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end do
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end do
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end if
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end subroutine static_screening_WB_pp
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