9
1
mirror of https://github.com/QuantumPackage/qp2.git synced 2024-10-07 16:37:19 +02:00
qp2/src/casscf_cipsi/densities_peter.irp.f

151 lines
5.2 KiB
Fortran
Raw Normal View History

2023-06-18 21:42:40 +02:00
use bitmasks
BEGIN_PROVIDER [real*8, P0tuvx_peter, (n_act_orb,n_act_orb,n_act_orb,n_act_orb) ]
BEGIN_DOC
! the second-order density matrix in the basis of the starting MOs
! matrices are state averaged
!
! we use the spin-free generators of mono-excitations
! E_pq destroys q and creates p
! D_pq = <0|E_pq|0> = D_qp
! P_pqrs = 1/2 <0|E_pq E_rs - delta_qr E_ps|0>
!
END_DOC
implicit none
integer :: t,u,v,x,mu,nu,istate,ispin,jspin,ihole,ipart,jhole,jpart
integer :: ierr
real*8 :: phase1,phase11,phase12,phase2,phase21,phase22
integer :: nu1,nu2,nu11,nu12,nu21,nu22
integer :: ierr1,ierr2,ierr11,ierr12,ierr21,ierr22
real*8 :: cI_mu(N_states),term
integer(bit_kind), dimension(N_int,2) :: det_mu, det_mu_ex
integer(bit_kind), dimension(N_int,2) :: det_mu_ex1, det_mu_ex11, det_mu_ex12
integer(bit_kind), dimension(N_int,2) :: det_mu_ex2, det_mu_ex21, det_mu_ex22
if (bavard) then
write(6,*) ' providing density matrix P0'
endif
P0tuvx_peter = 0.d0
! first loop: we apply E_tu, once for D_tu, once for -P_tvvu
do mu=1,n_det
call det_extract(det_mu,mu,N_int)
do istate=1,n_states
cI_mu(istate)=psi_coef(mu,istate)
end do
do t=1,n_act_orb
ipart=list_act(t)
do u=1,n_act_orb
ihole=list_act(u)
! apply E_tu
call det_copy(det_mu,det_mu_ex1,N_int)
call det_copy(det_mu,det_mu_ex2,N_int)
call do_spinfree_mono_excitation(det_mu,det_mu_ex1 &
,det_mu_ex2,nu1,nu2,ihole,ipart,phase1,phase2,ierr1,ierr2)
! det_mu_ex1 is in the list
if (nu1.ne.-1) then
do istate=1,n_states
term=cI_mu(istate)*psi_coef(nu1,istate)*phase1
! and we fill P0_tvvu
do v=1,n_act_orb
P0tuvx_peter(t,v,v,u)-=term
end do
end do
end if
! det_mu_ex2 is in the list
if (nu2.ne.-1) then
do istate=1,n_states
term=cI_mu(istate)*psi_coef(nu2,istate)*phase2
do v=1,n_act_orb
P0tuvx_peter(t,v,v,u)-=term
end do
end do
end if
end do
end do
end do
! now we do the double excitation E_tu E_vx |0>
do mu=1,n_det
call det_extract(det_mu,mu,N_int)
do istate=1,n_states
cI_mu(istate)=psi_coef(mu,istate)
end do
do v=1,n_act_orb
ipart=list_act(v)
do x=1,n_act_orb
ihole=list_act(x)
! apply E_vx
call det_copy(det_mu,det_mu_ex1,N_int)
call det_copy(det_mu,det_mu_ex2,N_int)
call do_spinfree_mono_excitation(det_mu,det_mu_ex1 &
,det_mu_ex2,nu1,nu2,ihole,ipart,phase1,phase2,ierr1,ierr2)
! we apply E_tu to the first resultant determinant, thus E_tu E_vx |0>
if (ierr1.eq.1) then
do t=1,n_act_orb
jpart=list_act(t)
do u=1,n_act_orb
jhole=list_act(u)
call det_copy(det_mu_ex1,det_mu_ex11,N_int)
call det_copy(det_mu_ex1,det_mu_ex12,N_int)
call do_spinfree_mono_excitation(det_mu_ex1,det_mu_ex11&
,det_mu_ex12,nu11,nu12,jhole,jpart,phase11,phase12,ierr11,ierr12)
if (nu11.ne.-1) then
do istate=1,n_states
P0tuvx_peter(t,u,v,x)+=cI_mu(istate)*psi_coef(nu11,istate)&
*phase11*phase1
end do
end if
if (nu12.ne.-1) then
do istate=1,n_states
P0tuvx_peter(t,u,v,x)+=cI_mu(istate)*psi_coef(nu12,istate)&
*phase12*phase1
end do
end if
end do
end do
end if
! we apply E_tu to the second resultant determinant
if (ierr2.eq.1) then
do t=1,n_act_orb
jpart=list_act(t)
do u=1,n_act_orb
jhole=list_act(u)
call det_copy(det_mu_ex2,det_mu_ex21,N_int)
call det_copy(det_mu_ex2,det_mu_ex22,N_int)
call do_spinfree_mono_excitation(det_mu_ex2,det_mu_ex21&
,det_mu_ex22,nu21,nu22,jhole,jpart,phase21,phase22,ierr21,ierr22)
if (nu21.ne.-1) then
do istate=1,n_states
P0tuvx_peter(t,u,v,x)+=cI_mu(istate)*psi_coef(nu21,istate)&
*phase21*phase2
end do
end if
if (nu22.ne.-1) then
do istate=1,n_states
P0tuvx_peter(t,u,v,x)+=cI_mu(istate)*psi_coef(nu22,istate)&
*phase22*phase2
end do
end if
end do
end do
end if
end do
end do
end do
! we average by just dividing by the number of states
do x=1,n_act_orb
do v=1,n_act_orb
do u=1,n_act_orb
do t=1,n_act_orb
P0tuvx_peter(t,u,v,x)*=0.5D0/dble(N_states)
end do
end do
end do
end do
END_PROVIDER