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https://github.com/pfloos/quack
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51 lines
1.3 KiB
Fortran
51 lines
1.3 KiB
Fortran
subroutine Bethe_Salpeter_B_matrix(eta,nBas,nC,nO,nV,nR,nS,lambda,ERI,OmRPA,rho_RPA,B_lr)
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! Compute the extra term for Bethe-Salpeter equation for linear response
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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) :: nBas,nC,nO,nV,nR,nS
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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) :: OmRPA(nS)
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double precision,intent(in) :: rho_RPA(nBas,nBas,nS)
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! Local variables
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double precision :: chi
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double precision :: eps
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integer :: i,j,a,b,ia,jb,kc
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! Output variables
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double precision,intent(out) :: B_lr(nS,nS)
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ia = 0
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do i=nC+1,nO
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do a=nO+1,nBas-nR
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ia = ia + 1
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jb = 0
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do j=nC+1,nO
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do b=nO+1,nBas-nR
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jb = jb + 1
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chi = 0d0
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do kc=1,nS
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eps = OmRPA(kc)**2 + eta**2
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! chi = chi + lambda*rho_RPA(i,b,kc)*rho_RPA(a,j,kc)*OmRPA(kc)/eps
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chi = chi + rho_RPA(i,b,kc)*rho_RPA(a,j,kc)*OmRPA(kc)/eps
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enddo
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B_lr(ia,jb) = B_lr(ia,jb) - lambda*ERI(i,j,b,a) + 4d0*lambda*chi
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enddo
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enddo
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enddo
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enddo
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end subroutine Bethe_Salpeter_B_matrix
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