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QuAcK/src/QuAcK/Bethe_Salpeter_A_matrix_dynamic.f90

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2020-04-22 00:39:52 +02:00
subroutine Bethe_Salpeter_A_matrix_dynamic(eta,nBas,nC,nO,nV,nR,nS,lambda,OmRPA,OmBSE,rho,A_lr)
! Compute the dynamic part of the Bethe-Salpeter equation matrices
implicit none
include 'parameters.h'
! Input variables
integer,intent(in) :: nBas,nC,nO,nV,nR,nS
double precision,intent(in) :: eta
double precision,intent(in) :: lambda
double precision,intent(in) :: OmRPA(nS)
double precision,intent(in) :: OmBSE(nS)
double precision,intent(in) :: rho(nBas,nBas,nS)
! Local variables
double precision :: chi
double precision :: eps
integer :: i,j,a,b,ia,jb,kc
! Output variables
double precision,intent(out) :: A_lr(nS,nS)
A_lr(:,:) = 0d0
ia = 0
do i=nC+1,nO
do a=nO+1,nBas-nR
ia = ia + 1
jb = 0
do j=nC+1,nO
do b=nO+1,nBas-nR
jb = jb + 1
chi = 0d0
do kc=1,nS
eps = OmRPA(kc)**2 + eta**2
chi = chi + rho(i,j,kc)*rho(a,b,kc)*OmRPA(kc)/eps
enddo
A_lr(ia,jb) = A_lr(ia,jb) - 4d0*lambda*chi
chi = 0d0
do kc=1,nS
eps = (OmBSE(kc) - OmRPA(kc))**2 + eta**2
chi = chi + rho(i,j,kc)*rho(a,b,kc)*(OmBSE(kc) - OmRPA(kc))/eps
eps = (OmBSE(kc) + OmRPA(kc))**2 + eta**2
chi = chi - rho(i,j,kc)*rho(a,b,kc)*(OmBSE(kc) + OmRPA(kc))/eps
enddo
A_lr(ia,jb) = A_lr(ia,jb) - 2d0*lambda*chi
enddo
enddo
enddo
enddo
end subroutine Bethe_Salpeter_A_matrix_dynamic