mirror of https://github.com/pfloos/quack
133 lines
2.8 KiB
Fortran
133 lines
2.8 KiB
Fortran
subroutine GW_ppBSE_static_kernel_C(ispin,eta,nBas,nC,nO,nV,nR,nS,nVV,lambda,ERI,Om,rho,KC)
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! Compute the VVVV 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) :: 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) :: Om(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,c,d,ab,cd,m
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! Output variables
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double precision,intent(out) :: KC(nVV,nVV)
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! Initialization
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KC(:,:) = 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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cd = 0
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do c=nO+1,nBas-nR
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do d=c,nBas-nR
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cd = cd + 1
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chi = 0d0
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do m=1,nS
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eps = Om(m)**2 + eta**2
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chi = chi - rho(a,c,m)*rho(b,d,m)*Om(m)/eps &
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+ rho(a,d,m)*rho(b,c,m)*Om(m)/eps
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end do
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KC(ab,cd) = 2d0*lambda*chi/sqrt((1d0 + Kronecker_delta(a,b))*(1d0 + Kronecker_delta(c,d)))
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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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cd = 0
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do c=nO+1,nBas-nR
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do d=c+1,nBas-nR
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cd = cd + 1
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chi = 0d0
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do m=1,nS
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eps = Om(m)**2 + eta**2
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chi = chi - rho(a,c,m)*rho(b,d,m)*Om(m)/eps &
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+ rho(a,d,m)*rho(b,c,m)*Om(m)/eps
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end do
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KC(ab,cd) = 2d0*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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!---------------!
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! SpinOrb block !
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!---------------!
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if(ispin == 4) 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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cd = 0
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do c=nO+1,nBas-nR
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do d=c+1,nBas-nR
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cd = cd + 1
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chi = 0d0
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do m=1,nS
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eps = Om(m)**2 + eta**2
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chi = chi - rho(a,c,m)*rho(b,d,m)*Om(m)/eps &
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+ rho(a,d,m)*rho(b,c,m)*Om(m)/eps
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end do
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KC(ab,cd) = 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
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