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https://github.com/pfloos/quack
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141 lines
3.5 KiB
Fortran
141 lines
3.5 KiB
Fortran
subroutine unrestricted_Bethe_Salpeter_A_matrix(eta,nBas,nC,nO,nV,nR,nSa,nSb,nSt,lambda,ERI_aaaa,ERI_aabb,ERI_bbbb,Omega,rho,A_lr)
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! Compute the extra term for Bethe-Salpeter equation for linear response in the unrestricted formalism
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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) :: nBas
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integer,intent(in) :: nC(nspin)
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integer,intent(in) :: nO(nspin)
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integer,intent(in) :: nV(nspin)
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integer,intent(in) :: nR(nspin)
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integer,intent(in) :: nSa
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integer,intent(in) :: nSb
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integer,intent(in) :: nSt
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double precision,intent(in) :: eta
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double precision,intent(in) :: lambda
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double precision,intent(in) :: ERI_aaaa(nBas,nBas,nBas,nBas)
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double precision,intent(in) :: ERI_aabb(nBas,nBas,nBas,nBas)
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double precision,intent(in) :: ERI_bbbb(nBas,nBas,nBas,nBas)
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double precision,intent(in) :: Omega(nSt)
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double precision,intent(in) :: rho(nBas,nBas,nSt,nspin)
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! Local variables
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double precision :: chi
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double precision :: eps
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integer :: i,j,a,b,ia,jb,kc
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! Output variables
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double precision,intent(out) :: A_lr(nSt,nSt)
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!--------------------------------!
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! Build part A of the BSE matrix !
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!--------------------------------!
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! alpha-alpha block
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ia = 0
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do i=nC(1)+1,nO(1)
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do a=nO(1)+1,nBas-nR(1)
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ia = ia + 1
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jb = 0
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do j=nC(1)+1,nO(1)
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do b=nO(1)+1,nBas-nR(1)
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jb = jb + 1
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chi = 0d0
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do kc=1,nSt
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eps = Omega(kc)**2 + eta**2
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chi = chi + rho(i,j,kc,1)*rho(a,b,kc,1)*Omega(kc)/eps &
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+ rho(i,j,kc,2)*rho(a,b,kc,2)*Omega(kc)/eps
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enddo
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A_lr(ia,jb) = A_lr(ia,jb) - lambda*ERI_aaaa(i,b,j,a) + 2d0*lambda*chi
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enddo
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enddo
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enddo
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enddo
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! alpha-beta block
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ia = 0
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do i=nC(1)+1,nO(1)
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do a=nO(1)+1,nBas-nR(1)
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ia = ia + 1
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jb = 0
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do j=nC(2)+1,nO(2)
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do b=nO(2)+1,nBas-nR(2)
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jb = jb + 1
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chi = 0d0
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do kc=1,nSt
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eps = Omega(kc)**2 + eta**2
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chi = chi + rho(i,j,kc,1)*rho(a,b,kc,1)*Omega(kc)/eps &
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+ rho(i,j,kc,2)*rho(a,b,kc,2)*Omega(kc)/eps
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enddo
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A_lr(ia,nSa+jb) = A_lr(ia,nSa+jb) - lambda*ERI_aabb(i,b,j,a) + 2d0*lambda*chi
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enddo
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enddo
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enddo
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enddo
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! beta-alpha block
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ia = 0
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do i=nC(2)+1,nO(2)
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do a=nO(2)+1,nBas-nR(2)
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ia = ia + 1
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jb = 0
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do j=nC(1)+1,nO(1)
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do b=nO(1)+1,nBas-nR(1)
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jb = jb + 1
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chi = 0d0
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do kc=1,nSt
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eps = Omega(kc)**2 + eta**2
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chi = chi + rho(i,j,kc,1)*rho(a,b,kc,1)*Omega(kc)/eps &
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+ rho(i,j,kc,2)*rho(a,b,kc,2)*Omega(kc)/eps
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enddo
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A_lr(nSa+ia,jb) = A_lr(nSa+ia,jb) - lambda*ERI_aabb(b,i,a,j) + 2d0*lambda*chi
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enddo
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enddo
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enddo
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enddo
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! beta-beta block
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ia = 0
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do i=nC(2)+1,nO(2)
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do a=nO(2)+1,nBas-nR(2)
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ia = ia + 1
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jb = 0
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do j=nC(2)+1,nO(2)
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do b=nO(2)+1,nBas-nR(2)
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jb = jb + 1
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chi = 0d0
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do kc=1,nSt
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eps = Omega(kc)**2 + eta**2
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chi = chi + rho(i,j,kc,1)*rho(a,b,kc,1)*Omega(kc)/eps &
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+ rho(i,j,kc,2)*rho(a,b,kc,2)*Omega(kc)/eps
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enddo
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A_lr(nSa+ia,nSa+jb) = A_lr(nSa+ia,nSa+jb) - lambda*ERI_bbbb(i,b,j,a) + 2d0*lambda*chi
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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 unrestricted_Bethe_Salpeter_A_matrix
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