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quack/src/RPA/linear_response_B_matrix.f90

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subroutine linear_response_B_matrix(ispin,dRPA,nBas,nC,nO,nV,nR,nS,lambda,ERI,B_lr)
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! Compute linear response
implicit none
include 'parameters.h'
! Input variables
logical,intent(in) :: dRPA
integer,intent(in) :: ispin,nBas,nC,nO,nV,nR,nS
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double precision,intent(in) :: lambda
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double precision,intent(in) :: ERI(nBas,nBas,nBas,nBas)
! Local variables
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double precision :: delta_dRPA
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integer :: i,j,a,b,ia,jb
! Output variables
double precision,intent(out) :: B_lr(nS,nS)
! Direct RPA
delta_dRPA = 0d0
if(dRPA) delta_dRPA = 1d0
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! Build B matrix for 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
B_lr(ia,jb) = 2d0*lambda*ERI(i,j,a,b) - (1d0 - delta_dRPA)*lambda*ERI(i,j,b,a)
end do
end do
end do
end do
end if
! Build B matrix for 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
B_lr(ia,jb) = - (1d0 - delta_dRPA)*lambda*ERI(i,j,b,a)
end do
end do
end do
end do
end if
! Build B matrix for spin orbitals
if(ispin == 3) 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
B_lr(ia,jb) = lambda*ERI(i,j,a,b) - (1d0 - delta_dRPA)*lambda*ERI(i,j,b,a)
end do
end do
end do
end do
end if
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end subroutine linear_response_B_matrix