=================== Perturbation Module =================== All subroutines in `*.irp.f` starting with ``pt2_`` in the current directory are perturbation computed using the routine ``i_H_psi``. Other cases are not allowed. The arguments of the ``pt2_`` are always: subroutine pt2_...( & psi_ref, & psi_ref_coefs, & E_refs, & det_pert, & c_pert, & e_2_pert, & H_pert_diag, & Nint, & ndet, & n_st ) integer, intent(in) :: Nint,ndet,n_st integer(bit_kind), intent(in) :: psi_ref(Nint,2,ndet) double precision , intent(in) :: psi_ref_coefs(ndet,n_st) double precision , intent(in) :: E_refs(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 psi_ref bitstring of the determinants present in the various n_st states psi_ref_coefs coefficients of the determinants on the various n_st states E_refs Energy of the various n_st states det_pert Perturber determinant c_pert Pertrubative coefficients for the various states e_2_pert Perturbative energetic contribution for the various states H_pert_diag Diagonal H matrix element of the perturber Nint Should be equal to N_int Ndet Number of determinants `i` in Psi on which we apply N_st Number of states Assumptions =========== * This is not allowed: subroutine & pt2_.... Needed Modules ============== .. Do not edit this section It was auto-generated .. by the `update_README.py` script. .. image:: tree_dependency.png * `Properties `_ * `Hartree_Fock `_ Needed Modules ============== .. Do not edit this section It was auto-generated .. by the `update_README.py` script. .. image:: tree_dependency.png * `Properties `_ * `Hartree_Fock `_ Documentation ============= .. Do not edit this section It was auto-generated .. by the `update_README.py` script. `do_pt2_end `_ If true, compute the PT2 at the end of the selection `fill_h_apply_buffer_selection `_ Fill the H_apply buffer with determiants for the selection `max_exc_pert `_ Undocumented `perturb_buffer_by_mono_delta_rho_one_point `_ Applly pertubration ``delta_rho_one_point`` to the buffer of determinants generated in the H_apply routine. `perturb_buffer_by_mono_dipole_moment_z `_ Applly pertubration ``dipole_moment_z`` to the buffer of determinants generated in the H_apply routine. `perturb_buffer_by_mono_epstein_nesbet `_ Applly pertubration ``epstein_nesbet`` to the buffer of determinants generated in the H_apply routine. `perturb_buffer_by_mono_epstein_nesbet_2x2 `_ Applly pertubration ``epstein_nesbet_2x2`` to the buffer of determinants generated in the H_apply routine. `perturb_buffer_by_mono_epstein_nesbet_sc2 `_ Applly pertubration ``epstein_nesbet_sc2`` to the buffer of determinants generated in the H_apply routine. `perturb_buffer_by_mono_epstein_nesbet_sc2_no_projected `_ Applly pertubration ``epstein_nesbet_sc2_no_projected`` to the buffer of determinants generated in the H_apply routine. `perturb_buffer_by_mono_epstein_nesbet_sc2_projected `_ Applly pertubration ``epstein_nesbet_sc2_projected`` to the buffer of determinants generated in the H_apply routine. `perturb_buffer_by_mono_h_core `_ Applly pertubration ``h_core`` to the buffer of determinants generated in the H_apply routine. `perturb_buffer_by_mono_moller_plesset `_ Applly pertubration ``moller_plesset`` to the buffer of determinants generated in the H_apply routine. `perturb_buffer_delta_rho_one_point `_ Applly pertubration ``delta_rho_one_point`` to the buffer of determinants generated in the H_apply routine. `perturb_buffer_dipole_moment_z `_ Applly pertubration ``dipole_moment_z`` to the buffer of determinants generated in the H_apply routine. `perturb_buffer_epstein_nesbet `_ Applly pertubration ``epstein_nesbet`` to the buffer of determinants generated in the H_apply routine. `perturb_buffer_epstein_nesbet_2x2 `_ Applly pertubration ``epstein_nesbet_2x2`` to the buffer of determinants generated in the H_apply routine. `perturb_buffer_epstein_nesbet_sc2 `_ Applly pertubration ``epstein_nesbet_sc2`` to the buffer of determinants generated in the H_apply routine. `perturb_buffer_epstein_nesbet_sc2_no_projected `_ Applly pertubration ``epstein_nesbet_sc2_no_projected`` to the buffer of determinants generated in the H_apply routine. `perturb_buffer_epstein_nesbet_sc2_projected `_ Applly pertubration ``epstein_nesbet_sc2_projected`` to the buffer of determinants generated in the H_apply routine. `perturb_buffer_h_core `_ Applly pertubration ``h_core`` to the buffer of determinants generated in the H_apply routine. `perturb_buffer_moller_plesset `_ Applly pertubration ``moller_plesset`` to the buffer of determinants generated in the H_apply routine. `pt2_delta_rho_one_point `_ compute the perturbatibe contribution to the Integrated Spin density at z = z_one point of one determinant .br for the various n_st states, at various level of theory. .br c_pert(i) = /( - ) .br e_2_pert(i) = c_pert(i) * .br H_pert_diag(i) = c_pert(i)^2 * .br To get the contribution of the first order : .br = sum(over i) e_2_pert(i) .br To get the contribution of the diagonal elements of the second order : .br [ + + sum(over i) H_pert_diag(i) ] / [1. + sum(over i) c_pert(i) **2] .br `pt2_dipole_moment_z `_ compute the perturbatibe contribution to the dipole moment of one determinant .br for the various n_st states, at various level of theory. .br c_pert(i) = /( - ) .br e_2_pert(i) = c_pert(i) * .br H_pert_diag(i) = c_pert(i)^2 * .br To get the contribution of the first order : .br = sum(over i) e_2_pert(i) .br To get the contribution of the diagonal elements of the second order : .br [ + + sum(over i) H_pert_diag(i) ] / [1. + sum(over i) c_pert(i) **2] .br `pt2_epstein_nesbet `_ compute the standard Epstein-Nesbet perturbative first order coefficient and second order energetic contribution .br for the various N_st states. .br c_pert(i) = /( E(i) - ) .br e_2_pert(i) = ^2/( E(i) - ) .br `pt2_epstein_nesbet_2x2 `_ compute the Epstein-Nesbet 2x2 diagonalization coefficient and energetic contribution .br for the various N_st states. .br e_2_pert(i) = 0.5 * (( - E(i) ) - sqrt( ( - E(i)) ^2 + 4 ^2 ) .br c_pert(i) = e_2_pert(i)/ .br `pt2_epstein_nesbet_sc2 `_ compute the standard Epstein-Nesbet perturbative first order coefficient and second order energetic contribution .br for the various N_st states, but with the CISD_SC2 energies and coefficients .br c_pert(i) = /( E(i) - ) .br e_2_pert(i) = ^2/( E(i) - ) .br `pt2_epstein_nesbet_sc2_no_projected `_ compute the Epstein-Nesbet perturbative first order coefficient and second order energetic contribution .br for the various N_st states, .br but with the correction in the denominator .br comming from the interaction of that determinant with all the others determinants .br that can be repeated by repeating all the double excitations .br : you repeat all the correlation energy already taken into account in CI_electronic_energy(1) .br that could be repeated to this determinant. .br In addition, for the perturbative energetic contribution you have the standard second order .br e_2_pert = ^2/(Delta_E) .br and also the purely projected contribution .br H_pert_diag = c_pert `pt2_epstein_nesbet_sc2_projected `_ compute the Epstein-Nesbet perturbative first order coefficient and second order energetic contribution .br for the various N_st states, .br but with the correction in the denominator .br comming from the interaction of that determinant with all the others determinants .br that can be repeated by repeating all the double excitations .br : you repeat all the correlation energy already taken into account in CI_electronic_energy(1) .br that could be repeated to this determinant. .br In addition, for the perturbative energetic contribution you have the standard second order .br e_2_pert = ^2/(Delta_E) .br and also the purely projected contribution .br H_pert_diag = c_pert `pt2_h_core `_ compute the standard Epstein-Nesbet perturbative first order coefficient and second order energetic contribution .br for the various N_st states. .br c_pert(i) = /( E(i) - ) .br e_2_pert(i) = ^2/( E(i) - ) .br `pt2_max `_ The selection process stops when the largest PT2 (for all the state) is lower than pt2_max in absolute value `pt2_moller_plesset `_ compute the standard Moller-Plesset perturbative first order coefficient and second order energetic contribution .br for the various n_st states. .br c_pert(i) = /(difference of orbital energies) .br e_2_pert(i) = ^2/(difference of orbital energies) .br `remove_small_contributions `_ Remove determinants with small contributions. N_states is assumed to be provided. `repeat_all_e_corr `_ Undocumented `selection_criterion `_ Threshold to select determinants. Set by selection routines. `selection_criterion_factor `_ Threshold to select determinants. Set by selection routines. `selection_criterion_min `_ Threshold to select determinants. Set by selection routines. `var_pt2_ratio `_ The selection process stops when the energy ratio variational/(variational+PT2) is equal to var_pt2_ratio