mirror of
https://github.com/LCPQ/quantum_package
synced 2024-11-08 07:03:57 +01:00
94 lines
3.2 KiB
Fortran
94 lines
3.2 KiB
Fortran
subroutine pt2_epstein_nesbet(det_pert,c_pert,e_2_pert,H_pert_diag,Nint,ndet,N_st)
|
|
use bitmasks
|
|
implicit none
|
|
integer, intent(in) :: Nint,ndet,N_st
|
|
integer(bit_kind), intent(in) :: det_pert(Nint,2)
|
|
double precision , intent(out) :: c_pert(N_st),e_2_pert(N_st),H_pert_diag(N_st)
|
|
double precision :: i_H_psi_array(N_st)
|
|
|
|
BEGIN_DOC
|
|
! compute the standard Epstein-Nesbet perturbative first order coefficient and second order energetic contribution
|
|
!
|
|
! for the various N_st states.
|
|
!
|
|
! c_pert(i) = <psi(i)|H|det_pert>/( E(i) - <det_pert|H|det_pert> )
|
|
!
|
|
! e_2_pert(i) = <psi(i)|H|det_pert>^2/( E(i) - <det_pert|H|det_pert> )
|
|
!
|
|
END_DOC
|
|
|
|
integer :: i,j
|
|
double precision :: diag_H_mat_elem, h
|
|
PROVIDE selection_criterion
|
|
|
|
ASSERT (Nint == N_int)
|
|
ASSERT (Nint > 0)
|
|
call i_H_psi(det_pert,psi_selectors,psi_selectors_coef,Nint,N_det_selectors,psi_selectors_size,N_st,i_H_psi_array)
|
|
h = diag_H_mat_elem(det_pert,Nint)
|
|
do i =1,N_st
|
|
if(CI_electronic_energy(i)>h.and.CI_electronic_energy(i).ne.0.d0)then
|
|
c_pert(i) = -1.d0
|
|
e_2_pert(i) = selection_criterion*selection_criterion_factor*2.d0
|
|
else if (dabs(CI_electronic_energy(i) - h) > 1.d-6) then
|
|
c_pert(i) = i_H_psi_array(i) / (CI_electronic_energy(i) - h)
|
|
H_pert_diag(i) = h*c_pert(i)*c_pert(i)
|
|
e_2_pert(i) = c_pert(i) * i_H_psi_array(i)
|
|
else
|
|
c_pert(i) = -1.d0
|
|
e_2_pert(i) = -dabs(i_H_psi_array(i))
|
|
H_pert_diag(i) = h
|
|
endif
|
|
enddo
|
|
|
|
end
|
|
|
|
subroutine pt2_epstein_nesbet_2x2(det_pert,c_pert,e_2_pert,H_pert_diag,Nint,ndet,N_st)
|
|
use bitmasks
|
|
implicit none
|
|
integer, intent(in) :: Nint,ndet,N_st
|
|
integer(bit_kind), intent(in) :: det_pert(Nint,2)
|
|
double precision , intent(out) :: c_pert(N_st),e_2_pert(N_st),H_pert_diag(N_st)
|
|
double precision :: i_H_psi_array(N_st)
|
|
|
|
BEGIN_DOC
|
|
! compute the Epstein-Nesbet 2x2 diagonalization coefficient and energetic contribution
|
|
!
|
|
! for the various N_st states.
|
|
!
|
|
! e_2_pert(i) = 0.5 * (( <det_pert|H|det_pert> - E(i) ) - sqrt( ( <det_pert|H|det_pert> - E(i)) ^2 + 4 <psi(i)|H|det_pert>^2 )
|
|
!
|
|
! c_pert(i) = e_2_pert(i)/ <psi(i)|H|det_pert>
|
|
!
|
|
END_DOC
|
|
|
|
integer :: i,j
|
|
double precision :: diag_H_mat_elem,delta_e, h
|
|
ASSERT (Nint == N_int)
|
|
ASSERT (Nint > 0)
|
|
PROVIDE CI_electronic_energy
|
|
|
|
call i_H_psi(det_pert,psi_selectors,psi_selectors_coef,Nint,N_det_selectors,psi_selectors_size,N_st,i_H_psi_array)
|
|
h = diag_H_mat_elem(det_pert,Nint)
|
|
do i =1,N_st
|
|
if (i_H_psi_array(i) /= 0.d0) then
|
|
delta_e = h - CI_electronic_energy(i)
|
|
if (delta_e > 0.d0) then
|
|
e_2_pert(i) = 0.5d0 * (delta_e - dsqrt(delta_e * delta_e + 4.d0 * i_H_psi_array(i) * i_H_psi_array(i)))
|
|
else
|
|
e_2_pert(i) = 0.5d0 * (delta_e + dsqrt(delta_e * delta_e + 4.d0 * i_H_psi_array(i) * i_H_psi_array(i)))
|
|
endif
|
|
if (dabs(i_H_psi_array(i)) > 1.d-6) then
|
|
c_pert(i) = e_2_pert(i)/i_H_psi_array(i)
|
|
else
|
|
c_pert(i) = 0.d0
|
|
endif
|
|
H_pert_diag(i) = h*c_pert(i)*c_pert(i)
|
|
else
|
|
e_2_pert(i) = 0.d0
|
|
c_pert(i) = 0.d0
|
|
H_pert_diag(i) = 0.d0
|
|
endif
|
|
enddo
|
|
|
|
end
|