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quantum_package/plugins/Perturbation/pert_sc2.irp.f

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subroutine pt2_epstein_nesbet_SC2_projected(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)
integer :: idx_repeat(0:ndet)
BEGIN_DOC
! compute the Epstein-Nesbet perturbative first order coefficient and second order energetic contribution
!
! for the various N_st states,
!
! but with the correction in the denominator
!
! comming from the interaction of that determinant with all the others determinants
!
! that can be repeated by repeating all the double excitations
!
! : you repeat all the correlation energy already taken into account in CI_electronic_energy(1)
!
! that could be repeated to this determinant.
!
! In addition, for the perturbative energetic contribution you have the standard second order
!
! e_2_pert = <psi_i|H|det_pert>^2/(Delta_E)
!
! and also the purely projected contribution
!
! H_pert_diag = <HF|H|det_pert> c_pert
END_DOC
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integer :: i,j,degree,l
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double precision :: diag_H_mat_elem,accu_e_corr,hij,h0j,h,delta_E
double precision :: repeat_all_e_corr,accu_e_corr_tmp,e_2_pert_fonda
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ASSERT (Nint == N_int)
ASSERT (Nint > 0)
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call i_H_psi_SC2(det_pert,psi_selectors,psi_selectors_coef,Nint,N_det_selectors,psi_selectors_size,N_st,i_H_psi_array,idx_repeat)
accu_e_corr = 0.d0
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!$IVDEP
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do i = 1, idx_repeat(0)
accu_e_corr = accu_e_corr + E_corr_per_selectors(idx_repeat(i))
enddo
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h = diag_H_mat_elem(det_pert,Nint) + accu_e_corr
delta_E = 1.d0/(CI_SC2_electronic_energy(1) - h)
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c_pert(1) = i_H_psi_array(1) /(CI_SC2_electronic_energy(1) - h)
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e_2_pert(1) = i_H_psi_array(1) * c_pert(1)
do i =2,N_st
H_pert_diag(i) = h
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if (dabs(CI_SC2_electronic_energy(i) - h) > 1.d-6) then
c_pert(i) = i_H_psi_array(i) / (-dabs(CI_SC2_electronic_energy(i) - h))
e_2_pert(i) = (c_pert(i) * i_H_psi_array(i))
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else
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c_pert(i) = i_H_psi_array(i)
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e_2_pert(i) = -dabs(i_H_psi_array(i))
endif
enddo
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degree = popcnt(xor( ref_bitmask(1,1), det_pert(1,1))) + &
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popcnt(xor( ref_bitmask(1,2), det_pert(1,2)))
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!DEC$ NOUNROLL
do l=2,Nint
degree = degree+ popcnt(xor( ref_bitmask(l,1), det_pert(l,1))) + &
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popcnt(xor( ref_bitmask(l,2), det_pert(l,2)))
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enddo
if(degree==4)then
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! <psi|delta_H|psi>
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e_2_pert_fonda = e_2_pert(1)
H_pert_diag(1) = e_2_pert(1) * c_pert(1) * c_pert(1)
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do i = 1, N_st
do j = 1, idx_repeat(0)
e_2_pert(i) += e_2_pert_fonda * psi_selectors_coef(idx_repeat(j),i) * psi_selectors_coef(idx_repeat(j),i)
enddo
enddo
endif
end
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subroutine pt2_epstein_nesbet_SC2_no_projected(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)
integer :: idx_repeat(0:ndet)
BEGIN_DOC
! compute the Epstein-Nesbet perturbative first order coefficient and second order energetic contribution
!
! for the various N_st states,
!
! but with the correction in the denominator
!
! comming from the interaction of that determinant with all the others determinants
!
! that can be repeated by repeating all the double excitations
!
! : you repeat all the correlation energy already taken into account in CI_electronic_energy(1)
!
! that could be repeated to this determinant.
!
! In addition, for the perturbative energetic contribution you have the standard second order
!
! e_2_pert = <psi_i|H|det_pert>^2/(Delta_E)
!
! and also the purely projected contribution
!
! H_pert_diag = <HF|H|det_pert> c_pert
END_DOC
integer :: i,j,degree,l
double precision :: diag_H_mat_elem,accu_e_corr,hij,h0j,h,delta_E
double precision :: repeat_all_e_corr,accu_e_corr_tmp,e_2_pert_fonda
ASSERT (Nint == N_int)
ASSERT (Nint > 0)
call i_H_psi_SC2(det_pert,psi_selectors,psi_selectors_coef,Nint,N_det_selectors,psi_selectors_size,N_st,i_H_psi_array,idx_repeat)
accu_e_corr = 0.d0
!$IVDEP
do i = 1, idx_repeat(0)
accu_e_corr = accu_e_corr + E_corr_per_selectors(idx_repeat(i))
enddo
h = diag_H_mat_elem(det_pert,Nint) + accu_e_corr
delta_E = 1.d0/(CI_SC2_electronic_energy(1) - h)
c_pert(1) = i_H_psi_array(1) /(CI_SC2_electronic_energy(1) - h)
e_2_pert(1) = i_H_psi_array(1) * c_pert(1)
do i =2,N_st
H_pert_diag(i) = h
if (dabs(CI_SC2_electronic_energy(i) - h) > 1.d-6) then
c_pert(i) = i_H_psi_array(i) / (-dabs(CI_SC2_electronic_energy(i) - h))
e_2_pert(i) = (c_pert(i) * i_H_psi_array(i))
else
c_pert(i) = i_H_psi_array(i)
e_2_pert(i) = -dabs(i_H_psi_array(i))
endif
enddo
end
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double precision function repeat_all_e_corr(key_in)
implicit none
integer(bit_kind), intent(in) :: key_in(N_int,2)
integer :: i,degree
double precision :: accu
use bitmasks
accu = 0.d0
call get_excitation_degree(key_in,ref_bitmask,degree,N_int)
if(degree==2)then
do i = 1, N_det_selectors
call get_excitation_degree(ref_bitmask,psi_selectors(1,1,i),degree,N_int)
if(degree.ne.2)cycle
call get_excitation_degree(key_in,psi_selectors(1,1,i),degree,N_int)
if (degree<=3)cycle
accu += E_corr_per_selectors(i)
enddo
elseif(degree==1)then
do i = 1, N_det_selectors
call get_excitation_degree(ref_bitmask,psi_selectors(1,1,i),degree,N_int)
if(degree.ne.2)cycle
call get_excitation_degree(key_in,psi_selectors(1,1,i),degree,N_int)
if (degree<=2)cycle
accu += E_corr_per_selectors(i)
enddo
endif
repeat_all_e_corr = accu
end
subroutine pt2_epstein_nesbet_sc2(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, but with the CISD_SC2 energies and coefficients
!
! 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
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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_SC2_electronic_energy(i)>h.and.CI_SC2_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_SC2_electronic_energy(i) - h) > 1.d-6) then
c_pert(i) = i_H_psi_array(i) / (CI_SC2_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