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quack/src/GF/BSE2_A_matrix_static.f90

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subroutine BSE2_A_matrix_static(ispin,eta,nBas,nC,nO,nV,nR,nS,lambda,ERI,eGF,A_sta)
! Compute the resonant part of the static BSE2 matrix
implicit none
include 'parameters.h'
! Input variables
integer,intent(in) :: ispin
integer,intent(in) :: nBas,nC,nO,nV,nR,nS
double precision,intent(in) :: eta
double precision,intent(in) :: lambda
double precision,intent(in) :: ERI(nBas,nBas,nBas,nBas)
double precision,intent(in) :: eGF(nBas)
! Local variables
double precision :: dem,num
integer :: i,j,k,l
integer :: a,b,c,d
integer :: ia,jb
! Output variables
double precision,intent(out) :: A_sta(nS,nS)
! Initialization
A_sta(:,:) = 0d0
! Second-order correlation kernel for the block A of the singlet manifold
if(ispin == 1) then
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
do k=nC+1,nO
do c=nO+1,nBas-nR
dem = - (eGF(c) - eGF(k))
num = 2d0*ERI(j,k,i,c)*ERI(a,c,b,k) - ERI(j,k,i,c)*ERI(a,c,k,b) &
- ERI(j,k,c,i)*ERI(a,c,b,k) + 2d0*ERI(j,k,c,i)*ERI(a,c,k,b)
A_sta(ia,jb) = A_sta(ia,jb) - num*dem/(dem**2 + eta**2)
dem = + (eGF(c) - eGF(k))
num = 2d0*ERI(j,c,i,k)*ERI(a,k,b,c) - ERI(j,c,i,k)*ERI(a,k,c,b) &
- ERI(j,c,k,i)*ERI(a,k,b,c) + 2d0*ERI(j,c,k,i)*ERI(a,k,c,b)
A_sta(ia,jb) = A_sta(ia,jb) + num*dem/(dem**2 + eta**2)
end do
end do
do c=nO+1,nBas-nR
do d=nO+1,nBas-nR
dem = - (eGF(c) + eGF(d))
num = 2d0*ERI(a,j,c,d)*ERI(c,d,i,b) - ERI(a,j,c,d)*ERI(c,d,b,i) &
- ERI(a,j,d,c)*ERI(c,d,i,b) + 2d0*ERI(a,j,d,c)*ERI(c,d,b,i)
A_sta(ia,jb) = A_sta(ia,jb) + 0.5d0*num*dem/(dem**2 + eta**2)
end do
end do
do k=nC+1,nO
do l=nC+1,nO
dem = - (eGF(k) + eGF(l))
num = 2d0*ERI(a,j,k,l)*ERI(k,l,i,b) - ERI(a,j,k,l)*ERI(k,l,b,i) &
- ERI(a,j,l,k)*ERI(k,l,i,b) + 2d0*ERI(a,j,l,k)*ERI(k,l,b,i)
A_sta(ia,jb) = A_sta(ia,jb) - 0.5d0*num*dem/(dem**2 + eta**2)
end do
end do
end do
end do
end do
end do
end if
! Second-order correlation kernel for the block A of the triplet manifold
if(ispin == 2) then
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
do k=nC+1,nO
do c=nO+1,nBas-nR
dem = - (eGF(c) - eGF(k))
num = 2d0*ERI(j,k,i,c)*ERI(a,c,b,k) - ERI(j,k,i,c)*ERI(a,c,k,b) - ERI(j,k,c,i)*ERI(a,c,b,k)
A_sta(ia,jb) = A_sta(ia,jb) - num*dem/(dem**2 + eta**2)
dem = + (eGF(c) - eGF(k))
num = 2d0*ERI(j,c,i,k)*ERI(a,k,b,c) - ERI(j,c,i,k)*ERI(a,k,c,b) - ERI(j,c,k,i)*ERI(a,k,b,c)
A_sta(ia,jb) = A_sta(ia,jb) + num*dem/(dem**2 + eta**2)
end do
end do
do c=nO+1,nBas-nR
do d=nO+1,nBas-nR
dem = - (eGF(c) + eGF(d))
num = ERI(a,j,c,d)*ERI(c,d,b,i) + ERI(a,j,d,c)*ERI(c,d,i,b)
A_sta(ia,jb) = A_sta(ia,jb) - 0.5d0*num*dem/(dem**2 + eta**2)
end do
end do
do k=nC+1,nO
do l=nC+1,nO
dem = - (eGF(k) + eGF(l))
num = ERI(a,j,k,l)*ERI(k,l,b,i) + ERI(a,j,l,k)*ERI(k,l,i,b)
A_sta(ia,jb) = A_sta(ia,jb) + 0.5d0*num*dem/(dem**2 + eta**2)
end do
end do
end do
end do
end do
end do
end if
end subroutine BSE2_A_matrix_static