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151 lines
5.2 KiB
Fortran
151 lines
5.2 KiB
Fortran
use bitmasks
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BEGIN_PROVIDER [real*8, P0tuvx_peter, (n_act_orb,n_act_orb,n_act_orb,n_act_orb) ]
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BEGIN_DOC
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! the second-order density matrix in the basis of the starting MOs
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! matrices are state averaged
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!
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! we use the spin-free generators of mono-excitations
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! E_pq destroys q and creates p
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! D_pq = <0|E_pq|0> = D_qp
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! P_pqrs = 1/2 <0|E_pq E_rs - delta_qr E_ps|0>
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!
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END_DOC
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implicit none
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integer :: t,u,v,x,mu,nu,istate,ispin,jspin,ihole,ipart,jhole,jpart
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integer :: ierr
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real*8 :: phase1,phase11,phase12,phase2,phase21,phase22
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integer :: nu1,nu2,nu11,nu12,nu21,nu22
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integer :: ierr1,ierr2,ierr11,ierr12,ierr21,ierr22
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real*8 :: cI_mu(N_states),term
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integer(bit_kind), dimension(N_int,2) :: det_mu, det_mu_ex
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integer(bit_kind), dimension(N_int,2) :: det_mu_ex1, det_mu_ex11, det_mu_ex12
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integer(bit_kind), dimension(N_int,2) :: det_mu_ex2, det_mu_ex21, det_mu_ex22
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if (bavard) then
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write(6,*) ' providing density matrix P0'
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endif
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P0tuvx_peter = 0.d0
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! first loop: we apply E_tu, once for D_tu, once for -P_tvvu
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do mu=1,n_det
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call det_extract(det_mu,mu,N_int)
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do istate=1,n_states
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cI_mu(istate)=psi_coef(mu,istate)
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end do
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do t=1,n_act_orb
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ipart=list_act(t)
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do u=1,n_act_orb
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ihole=list_act(u)
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! apply E_tu
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call det_copy(det_mu,det_mu_ex1,N_int)
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call det_copy(det_mu,det_mu_ex2,N_int)
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call do_spinfree_mono_excitation(det_mu,det_mu_ex1 &
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,det_mu_ex2,nu1,nu2,ihole,ipart,phase1,phase2,ierr1,ierr2)
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! det_mu_ex1 is in the list
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if (nu1.ne.-1) then
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do istate=1,n_states
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term=cI_mu(istate)*psi_coef(nu1,istate)*phase1
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! and we fill P0_tvvu
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do v=1,n_act_orb
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P0tuvx_peter(t,v,v,u)-=term
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end do
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end do
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end if
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! det_mu_ex2 is in the list
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if (nu2.ne.-1) then
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do istate=1,n_states
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term=cI_mu(istate)*psi_coef(nu2,istate)*phase2
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do v=1,n_act_orb
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P0tuvx_peter(t,v,v,u)-=term
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end do
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end do
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end if
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end do
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end do
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end do
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! now we do the double excitation E_tu E_vx |0>
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do mu=1,n_det
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call det_extract(det_mu,mu,N_int)
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do istate=1,n_states
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cI_mu(istate)=psi_coef(mu,istate)
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end do
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do v=1,n_act_orb
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ipart=list_act(v)
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do x=1,n_act_orb
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ihole=list_act(x)
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! apply E_vx
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call det_copy(det_mu,det_mu_ex1,N_int)
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call det_copy(det_mu,det_mu_ex2,N_int)
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call do_spinfree_mono_excitation(det_mu,det_mu_ex1 &
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,det_mu_ex2,nu1,nu2,ihole,ipart,phase1,phase2,ierr1,ierr2)
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! we apply E_tu to the first resultant determinant, thus E_tu E_vx |0>
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if (ierr1.eq.1) then
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do t=1,n_act_orb
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jpart=list_act(t)
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do u=1,n_act_orb
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jhole=list_act(u)
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call det_copy(det_mu_ex1,det_mu_ex11,N_int)
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call det_copy(det_mu_ex1,det_mu_ex12,N_int)
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call do_spinfree_mono_excitation(det_mu_ex1,det_mu_ex11&
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,det_mu_ex12,nu11,nu12,jhole,jpart,phase11,phase12,ierr11,ierr12)
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if (nu11.ne.-1) then
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do istate=1,n_states
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P0tuvx_peter(t,u,v,x)+=cI_mu(istate)*psi_coef(nu11,istate)&
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*phase11*phase1
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end do
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end if
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if (nu12.ne.-1) then
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do istate=1,n_states
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P0tuvx_peter(t,u,v,x)+=cI_mu(istate)*psi_coef(nu12,istate)&
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*phase12*phase1
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end do
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end if
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end do
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end do
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end if
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! we apply E_tu to the second resultant determinant
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if (ierr2.eq.1) then
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do t=1,n_act_orb
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jpart=list_act(t)
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do u=1,n_act_orb
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jhole=list_act(u)
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call det_copy(det_mu_ex2,det_mu_ex21,N_int)
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call det_copy(det_mu_ex2,det_mu_ex22,N_int)
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call do_spinfree_mono_excitation(det_mu_ex2,det_mu_ex21&
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,det_mu_ex22,nu21,nu22,jhole,jpart,phase21,phase22,ierr21,ierr22)
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if (nu21.ne.-1) then
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do istate=1,n_states
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P0tuvx_peter(t,u,v,x)+=cI_mu(istate)*psi_coef(nu21,istate)&
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*phase21*phase2
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end do
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end if
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if (nu22.ne.-1) then
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do istate=1,n_states
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P0tuvx_peter(t,u,v,x)+=cI_mu(istate)*psi_coef(nu22,istate)&
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*phase22*phase2
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end do
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end if
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end do
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end do
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end if
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end do
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end do
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end do
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! we average by just dividing by the number of states
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do x=1,n_act_orb
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do v=1,n_act_orb
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do u=1,n_act_orb
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do t=1,n_act_orb
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P0tuvx_peter(t,u,v,x)*=0.5D0/dble(N_states)
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end do
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end do
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end do
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end do
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END_PROVIDER
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