2020-10-05 16:58:19 +02:00
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subroutine unrestricted_S2_expval(ispin,nBas,nC,nO,nV,nR,nS,nSa,nSb,nSt,maxS,c,S,XpY,XmY,S2)
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! Compute <S**2> for linear response excited states
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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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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) :: nS(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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integer,intent(in) :: maxS
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double precision,intent(in) :: c(nBas,nBas,nspin)
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double precision,intent(in) :: S(nBas,nBas)
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double precision,intent(in) :: XpY(nSt,nSt)
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double precision,intent(in) :: XmY(nSt,nSt)
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! Local variables
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integer :: m
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integer :: ia,i,a
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double precision :: S2_exact
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double precision :: S2_gs
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double precision,allocatable :: Xa(:,:), Xb(:,:), Ya(:,:), Yb(:,:)
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double precision,allocatable :: Xat(:,:),Xbt(:,:),Yat(:,:),Ybt(:,:)
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double precision,allocatable :: OO(:,:), OV(:,:), VO(:,:), VV(:,:)
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double precision,allocatable :: OOt(:,:),OVt(:,:),VOt(:,:),VVt(:,:)
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double precision,external :: trace_matrix
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! Output variables
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double precision,intent(out) :: S2(maxS)
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! Memory allocation
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allocate(OO(nO(1)-nC(1),nO(2)-nC(2)), OV(nO(1)-nC(1),nV(2)-nR(2)), VO(nV(1)-nR(1),nO(2)-nC(2)), VV(nV(1)-nR(1),nV(2)-nR(2)), &
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OOt(nO(2)-nC(2),nO(1)-nC(1)),OVt(nV(2)-nR(2),nO(1)-nC(1)),VOt(nO(2)-nC(2),nV(1)-nR(1)),VVt(nV(2)-nR(2),nV(1)-nR(1)))
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! Overlap matrix between spin-up and spin-down orbitals
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OO(:,:) = matmul(transpose(c(:,nC(1)+1:nO(1) ,1)),matmul(S,c(:,nC(2)+1:nO(2) ,2)))
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OV(:,:) = matmul(transpose(c(:,nC(1)+1:nO(1) ,1)),matmul(S,c(:,nO(2)+1:nBas-nR(2),2)))
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VO(:,:) = matmul(transpose(c(:,nO(1)+1:nBas-nR(1),1)),matmul(S,c(:,nC(2)+1:nO(2) ,2)))
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VV(:,:) = matmul(transpose(c(:,nO(1)+1:nBas-nR(1),1)),matmul(S,c(:,nO(2)+1:nBas-nR(2),2)))
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OOt(:,:) = transpose(OO(:,:))
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OVt(:,:) = transpose(OV(:,:))
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VOt(:,:) = transpose(VO(:,:))
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VVt(:,:) = transpose(VV(:,:))
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!-------------------------!
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! <S**2> for ground state !
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!-------------------------!
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S2_exact = dble(nO(1) - nO(2))/2d0*(dble(nO(1) - nO(2))/2d0 + 1d0)
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S2_gs = S2_exact + nO(2) - sum(OO(:,:)**2)
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!------------------------------------------!
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! <S**2> for spin-conserved-excited states !
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!------------------------------------------!
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if(ispin == 1) then
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allocate(Xa(nO(1)-nC(1),nV(1)-nR(1)), Ya(nO(1)-nC(1),nV(1)-nR(1)), Xb(nO(2)-nC(2),nV(2)-nR(2)), Yb(nO(2)-nC(2),nV(2)-nR(2)), &
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Xat(nV(1)-nR(1),nO(1)-nC(1)),Yat(nV(1)-nR(1),nO(1)-nC(1)),Xbt(nV(2)-nR(2),nO(2)-nC(2)),Ybt(nV(2)-nR(2),nO(2)-nC(2)))
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do m=1,maxS
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ia = 0
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do i=nC(1)+1,nO(1)
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do a=1,nV(1)-nR(1)
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ia = ia + 1
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Xa(i,a) = 0.5d0*(XpY(m,ia) + XmY(m,ia))
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Ya(i,a) = 0.5d0*(XpY(m,ia) - XmY(m,ia))
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end do
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end do
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ia = 0
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do i=nC(2)+1,nO(2)
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do a=1,nV(2)-nR(2)
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ia = ia + 1
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Xb(i,a) = 0.5d0*(XpY(m,nSa+ia) + XmY(m,nSa+ia))
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Yb(i,a) = 0.5d0*(XpY(m,nSa+ia) - XmY(m,nSa+ia))
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end do
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end do
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Xat(:,:) = transpose(Xa(:,:))
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Xbt(:,:) = transpose(Xb(:,:))
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Yat(:,:) = transpose(Ya(:,:))
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Ybt(:,:) = transpose(Yb(:,:))
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S2(m) = S2_gs &
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+ trace_matrix(nV(1),matmul(Xat,matmul(OO,matmul(OOt,Xa)))) &
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+ trace_matrix(nV(2),matmul(Xbt,matmul(OOt,matmul(OO,Xb)))) &
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- trace_matrix(nO(1),matmul(Xa,matmul(VO,matmul(VOt,Xat)))) &
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- trace_matrix(nO(2),matmul(Xb,matmul(OVt,matmul(OV,Xbt)))) &
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- 2d0*trace_matrix(nO(1),matmul(OO,matmul(Xb,matmul(VVt,Xat)))) &
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- 2d0*trace_matrix(nV(2),matmul(OVt,matmul(Xa,matmul(VO,Yb)))) &
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- 2d0*trace_matrix(nV(1),matmul(VO,matmul(Xb,matmul(OVt,Ya)))) &
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- trace_matrix(nV(1),matmul(Yat,matmul(OO,matmul(OOt,Ya)))) &
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- trace_matrix(nV(2),matmul(Ybt,matmul(OOt,matmul(OO,Yb)))) &
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+ trace_matrix(nO(1),matmul(Ya,matmul(VO,matmul(VOt,Yat)))) &
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+ trace_matrix(nO(2),matmul(Yb,matmul(OVt,matmul(OV,Ybt)))) &
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+ 2d0*trace_matrix(nO(1),matmul(Ya,matmul(VV,matmul(Ybt,OOt))))
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end do
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end if
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!------------------------------------------!
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! <S**2> for spin-conserved-excited states !
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!------------------------------------------!
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if(ispin == 2) then
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allocate(Xa(nO(1)-nC(1),nV(2)-nR(2)), Ya(nO(1)-nC(1),nV(2)-nR(2)), Xb(nO(2)-nC(2),nV(1)-nR(1)), Yb(nO(2)-nC(2),nV(1)-nR(1)), &
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Xat(nV(2)-nR(2),nO(1)-nC(1)),Yat(nV(2)-nR(2),nO(1)-nC(1)),Xbt(nV(1)-nR(1),nO(2)-nC(2)),Ybt(nV(1)-nR(1),nO(2)-nC(2)))
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do m=1,maxS
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ia = 0
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do i=nC(1)+1,nO(1)
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do a=1,nV(2)-nR(2)
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ia = ia + 1
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Xa(i,a) = 0.5d0*(XpY(m,ia) + XmY(m,ia))
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Ya(i,a) = 0.5d0*(XpY(m,ia) - XmY(m,ia))
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end do
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end do
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ia = 0
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do i=nC(2)+1,nO(2)
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do a=1,nV(1)-nR(1)
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ia = ia + 1
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Xb(i,a) = 0.5d0*(XpY(m,nSa+ia) + XmY(m,nSa+ia))
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Yb(i,a) = 0.5d0*(XpY(m,nSa+ia) - XmY(m,nSa+ia))
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end do
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end do
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Xat(:,:) = transpose(Xa(:,:))
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Xbt(:,:) = transpose(Xb(:,:))
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Yat(:,:) = transpose(Ya(:,:))
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Ybt(:,:) = transpose(Yb(:,:))
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2020-10-05 23:00:56 +02:00
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S2(m) = S2_gs &
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+ trace_matrix(nV(1),matmul(Xbt,matmul(OOt,matmul(OO,Xb)))) &
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- trace_matrix(nO(2),matmul(Xb,matmul(VO,matmul(VOt,Xbt)))) &
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+ trace_matrix(nO(2),matmul(Xb,VO))**2 &
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+ trace_matrix(nV(2),matmul(Yat,matmul(OO,matmul(OOt,Ya)))) &
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+ trace_matrix(nO(1),matmul(Ya,matmul(OVt,matmul(OV,Yat)))) &
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+ trace_matrix(nO(1),matmul(Ya,OVt))**2 &
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- 2d0*trace_matrix(nO(2),matmul(Xb,VO))*trace_matrix(nO(1),matmul(Ya,OVt)) &
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+ trace_matrix(nV(2),matmul(Xat,matmul(OO,matmul(OOt,Xa)))) &
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- trace_matrix(nO(1),matmul(Xa,matmul(OVt,matmul(OV,Xat)))) &
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+ trace_matrix(nO(1),matmul(Xa,OVt))**2 &
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+ trace_matrix(nV(1),matmul(Ybt,matmul(OOt,matmul(OO,Yb)))) &
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- trace_matrix(nO(2),matmul(Yb,matmul(VO,matmul(VOt,Ybt)))) &
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+ trace_matrix(nV(1),matmul(Ybt,VOt))**2 &
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- 2d0*trace_matrix(nO(1),matmul(Xa,OVt))*trace_matrix(nO(2),matmul(Yb,VO))
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2020-10-05 16:58:19 +02:00
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end do
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end if
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end subroutine unrestricted_S2_expval
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