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https://github.com/pfloos/quack
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58 lines
1.3 KiB
Fortran
58 lines
1.3 KiB
Fortran
subroutine linear_response_C_pp(ispin,dRPA,nBas,nC,nO,nV,nR,nOO,nVV,e,ERI,C_pp)
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! Compute the C matrix of the pp channel
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implicit none
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include 'parameters.h'
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! Input variables
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integer,intent(in) :: ispin
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logical,intent(in) :: dRPA
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integer,intent(in) :: nBas,nC,nO,nV,nR,nOO,nVV
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double precision,intent(in) :: e(nBas),ERI(nBas,nBas,nBas,nBas)
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! Local variables
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double precision :: delta_spin
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double precision :: delta_dRPA
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double precision,external :: Kronecker_delta
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integer :: a,b,c,d,ab,cd
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! Output variables
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double precision,intent(out) :: C_pp(nVV,nVV)
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! Singlet or triplet manifold?
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delta_spin = 0d0
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if(ispin == 1) delta_spin = +1d0
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if(ispin == 2) delta_spin = -1d0
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! Direct RPA
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delta_dRPA = 0d0
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if(dRPA) delta_dRPA = 1d0
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! Build A matrix
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ab = 0
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do a=nO+1,nBas-nR
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do b=nO+1,nBas-nR
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ab = ab + 1
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cd = 0
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do c=nO+1,nBas-nR
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do d=nO+1,nBas-nR
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cd = cd + 1
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C_pp(ab,cd) = (e(a) + e(b))*Kronecker_delta(a,c)*Kronecker_delta(b,d) &
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+ (1d0 + delta_spin)*ERI(a,b,c,d) - (1d0 - delta_dRPA)*ERI(a,b,d,c)
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enddo
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enddo
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enddo
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enddo
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end subroutine linear_response_C_pp
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