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mirror of https://github.com/pfloos/quack synced 2024-11-19 04:22:39 +01:00
quack/src/LR/unrestricted_linear_response_B_matrix.f90

170 lines
3.6 KiB
Fortran

subroutine unrestricted_linear_response_B_matrix(ispin,dRPA,nBas,nC,nO,nV,nR,nSa,nSb,nSt,lambda, &
ERI_aaaa,ERI_aabb,ERI_bbbb,B_lr)
! Compute linear response
implicit none
include 'parameters.h'
! Input variables
logical,intent(in) :: dRPA
integer,intent(in) :: ispin
integer,intent(in) :: nBas
integer,intent(in) :: nC(nspin)
integer,intent(in) :: nO(nspin)
integer,intent(in) :: nV(nspin)
integer,intent(in) :: nR(nspin)
integer,intent(in) :: nSa
integer,intent(in) :: nSb
integer,intent(in) :: nSt
double precision,intent(in) :: lambda
double precision,intent(in) :: ERI_aaaa(nBas,nBas,nBas,nBas)
double precision,intent(in) :: ERI_aabb(nBas,nBas,nBas,nBas)
double precision,intent(in) :: ERI_bbbb(nBas,nBas,nBas,nBas)
! Local variables
double precision :: delta_dRPA
double precision,external :: Kronecker_delta
integer :: i,j,a,b,ia,jb
! Output variables
double precision,intent(out) :: B_lr(nSt,nSt)
! Direct RPA
delta_dRPA = 0d0
if(dRPA) delta_dRPA = 1d0
!-----------------------------------------------
! Build B matrix for spin-conserving transitions
!-----------------------------------------------
if(ispin == 1) then
! aaaa block
ia = 0
do i=nC(1)+1,nO(1)
do a=nO(1)+1,nBas-nR(1)
ia = ia + 1
jb = 0
do j=nC(1)+1,nO(1)
do b=nO(1)+1,nBas-nR(1)
jb = jb + 1
B_lr(ia,jb) = lambda*ERI_aaaa(i,j,a,b) - (1d0 - delta_dRPA)*lambda*ERI_aaaa(i,j,b,a)
end do
end do
end do
end do
! aabb block
ia = 0
do i=nC(1)+1,nO(1)
do a=nO(1)+1,nBas-nR(1)
ia = ia + 1
jb = 0
do j=nC(2)+1,nO(2)
do b=nO(2)+1,nBas-nR(2)
jb = jb + 1
B_lr(ia,nSa+jb) = lambda*ERI_aabb(i,j,a,b)
end do
end do
end do
end do
! bbaa block
ia = 0
do i=nC(2)+1,nO(2)
do a=nO(2)+1,nBas-nR(2)
ia = ia + 1
jb = 0
do j=nC(1)+1,nO(1)
do b=nO(1)+1,nBas-nR(1)
jb = jb + 1
B_lr(nSa+ia,jb) = lambda*ERI_aabb(j,i,b,a)
end do
end do
end do
end do
! bbbb block
ia = 0
do i=nC(2)+1,nO(2)
do a=nO(2)+1,nBas-nR(2)
ia = ia + 1
jb = 0
do j=nC(2)+1,nO(2)
do b=nO(2)+1,nBas-nR(2)
jb = jb + 1
B_lr(nSa+ia,nSa+jb) = lambda*ERI_bbbb(i,j,a,b) - (1d0 - delta_dRPA)*lambda*ERI_bbbb(i,j,b,a)
end do
end do
end do
end do
end if
!-----------------------------------------------
! Build B matrix for spin-flip transitions
!-----------------------------------------------
if(ispin == 2) then
B_lr(:,:) = 0d0
! abba block
ia = 0
do i=nC(1)+1,nO(1)
do a=nO(2)+1,nBas-nR(2)
ia = ia + 1
jb = 0
do j=nC(2)+1,nO(2)
do b=nO(1)+1,nBas-nR(1)
jb = jb + 1
B_lr(ia,nSa+jb) = - (1d0 - delta_dRPA)*lambda*ERI_aabb(i,j,b,a)
end do
end do
end do
end do
! baab block
ia = 0
do i=nC(2)+1,nO(2)
do a=nO(1)+1,nBas-nR(1)
ia = ia + 1
jb = 0
do j=nC(1)+1,nO(1)
do b=nO(2)+1,nBas-nR(2)
jb = jb + 1
B_lr(nSa+ia,jb) = - (1d0 - delta_dRPA)*lambda*ERI_aabb(j,i,a,b)
end do
end do
end do
end do
end if
end subroutine unrestricted_linear_response_B_matrix