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quack/src/LR/linear_response_C_pp_od.f90

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2021-11-18 13:34:08 +01:00
subroutine linear_response_C_pp_od(ispin,nBas,nC,nO,nV,nR,nOO,nVV,lambda,ERI,C_pp)
! Compute the C matrix of the pp channel (without diagonal term)
implicit none
include 'parameters.h'
! Input variables
integer,intent(in) :: ispin
integer,intent(in) :: nBas,nC,nO,nV,nR,nOO,nVV
double precision,intent(in) :: lambda
double precision,intent(in) :: ERI(nBas,nBas,nBas,nBas)
! Local variables
double precision,external :: Kronecker_delta
integer :: a,b,c,d,ab,cd
! Output variables
double precision,intent(out) :: C_pp(nVV,nVV)
! Build C matrix for the singlet manifold
if(ispin == 1) then
ab = 0
do a=nO+1,nBas-nR
do b=a,nBas-nR
ab = ab + 1
cd = 0
do c=nO+1,nBas-nR
do d=c,nBas-nR
cd = cd + 1
C_pp(ab,cd) = lambda*(ERI(a,b,c,d) + ERI(a,b,d,c))/sqrt((1d0 + Kronecker_delta(a,b))*(1d0 + Kronecker_delta(c,d)))
end do
end do
end do
end do
end if
! Build C matrix for the triplet manifold, or alpha-alpha block, or in the spin-orbital basis
if(ispin == 2 .or. ispin == 4) then
ab = 0
do a=nO+1,nBas-nR
do b=a+1,nBas-nR
ab = ab + 1
cd = 0
do c=nO+1,nBas-nR
do d=c+1,nBas-nR
cd = cd + 1
C_pp(ab,cd) = lambda*(ERI(a,b,c,d) - ERI(a,b,d,c))
end do
end do
end do
end do
end if
! Build the alpha-beta block of the C matrix
if(ispin == 3) then
ab = 0
do a=nO+1,nBas-nR
do b=nO+1,nBas-nR
ab = ab + 1
cd = 0
do c=nO+1,nBas-nR
do d=nO+1,nBas-nR
cd = cd + 1
C_pp(ab,cd) = lambda*ERI(a,b,c,d)
end do
end do
end do
end do
end if
end subroutine linear_response_C_pp_od