quantum_package/docs/source/modules/perturbation.rst

.. _perturbation:

.. program:: perturbation

.. default-role:: option

============
Perturbation
============


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:

.. code-block:: fortran

  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`
  Perturbative 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 <det_pert | |H| | `i`>

`N_st`
  Number of states






EZFIO parameters
----------------

.. option:: do_pt2

    If `True`, compute the |PT2| contribution

    Default: True

.. option:: pt2_max

    The selection process stops when the largest |PT2| (for all the state) is lower

    than `pt2_max` in absolute value

    Default: 0.0001

.. option:: pt2_relative_error

    Stop stochastic |PT2| when the relative error is smaller than `PT2_relative_error`

    Default: 0.005

.. option:: correlation_energy_ratio_max

    The selection process stops at a fixed correlation ratio (useful for getting same accuracy between molecules).

    Defined as :math:`{E_{CI}-E_{HF}}/{E_{CI}+E_{PT2} - E_{HF}}`.

    Default: 1.00

.. option:: h0_type

    Type of zeroth-order Hamiltonian [ EN | Barycentric | Variance | SOP ]

    Default: EN


Providers
---------


.. c:var:: fill_h_apply_buffer_selection

    .. code:: text

        subroutine fill_H_apply_buffer_selection(n_selected,det_buffer,e_2_pert_buffer,coef_pert_buffer, &
        N_st,Nint,iproc,select_max_out)

    File: :file:`selection.irp.f`

    Fill the H_apply buffer with determiants for the selection




.. c:var:: max_exc_pert

    .. code:: text

        integer	:: max_exc_pert

    File: :file:`exc_max.irp.f`

    




.. c:var:: selection_criterion

    .. code:: text

        double precision	:: selection_criterion
        double precision	:: selection_criterion_min
        double precision	:: selection_criterion_factor

    File: :file:`selection.irp.f`

    Threshold to select determinants. Set by selection routines.




.. c:var:: selection_criterion_factor

    .. code:: text

        double precision	:: selection_criterion
        double precision	:: selection_criterion_min
        double precision	:: selection_criterion_factor

    File: :file:`selection.irp.f`

    Threshold to select determinants. Set by selection routines.




.. c:var:: selection_criterion_min

    .. code:: text

        double precision	:: selection_criterion
        double precision	:: selection_criterion_min
        double precision	:: selection_criterion_factor

    File: :file:`selection.irp.f`

    Threshold to select determinants. Set by selection routines.




.. c:var:: var_pt2_ratio

    .. code:: text

        double precision	:: var_pt2_ratio

    File: :file:`var_pt2_ratio_provider.irp.f`

    The selection process stops when the energy ratio variational/(variational+PT2) is equal to var_pt2_ratio




Subroutines / functions
-----------------------



.. c:function:: i_h_psi_pert_new_minilist

    .. code:: text

        subroutine i_H_psi_pert_new_minilist(key,keys,idx_key,N_minilist,coef,Nint,Ndet,Ndet_max,Nstate,i_H_psi_array,coef_pert)

    File: :file:`pt2_new.irp.f`

    Computes <i|H|Psi> = \sum_J c_J <i|H|J>. 
    Uses filter_connected_i_H_psi0 to get all the |J> to which |i> is connected. The |J> are searched in short pre-computed lists.





.. c:function:: perturb_buffer_by_mono_decontracted

    .. code:: text

        subroutine perturb_buffer_by_mono_decontracted(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``decontracted`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_by_mono_dummy

    .. code:: text

        subroutine perturb_buffer_by_mono_dummy(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``dummy`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_by_mono_epstein_nesbet

    .. code:: text

        subroutine perturb_buffer_by_mono_epstein_nesbet(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``epstein_nesbet`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_by_mono_epstein_nesbet_2x2

    .. code:: text

        subroutine perturb_buffer_by_mono_epstein_nesbet_2x2(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``epstein_nesbet_2x2`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_by_mono_epstein_nesbet_2x2_no_ci_diag

    .. code:: text

        subroutine perturb_buffer_by_mono_epstein_nesbet_2x2_no_ci_diag(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``epstein_nesbet_2x2_no_ci_diag`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_by_mono_epstein_nesbet_sc2

    .. code:: text

        subroutine perturb_buffer_by_mono_epstein_nesbet_sc2(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``epstein_nesbet_sc2`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_by_mono_epstein_nesbet_sc2_no_projected

    .. code:: text

        subroutine perturb_buffer_by_mono_epstein_nesbet_sc2_no_projected(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``epstein_nesbet_sc2_no_projected`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_by_mono_epstein_nesbet_sc2_projected

    .. code:: text

        subroutine perturb_buffer_by_mono_epstein_nesbet_sc2_projected(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``epstein_nesbet_sc2_projected`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_by_mono_h_core

    .. code:: text

        subroutine perturb_buffer_by_mono_h_core(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``h_core`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_by_mono_moller_plesset

    .. code:: text

        subroutine perturb_buffer_by_mono_moller_plesset(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``moller_plesset`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_by_mono_moller_plesset_general

    .. code:: text

        subroutine perturb_buffer_by_mono_moller_plesset_general(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``moller_plesset_general`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_by_mono_qdpt

    .. code:: text

        subroutine perturb_buffer_by_mono_qdpt(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``qdpt`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_decontracted

    .. code:: text

        subroutine perturb_buffer_decontracted(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``decontracted`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_dummy

    .. code:: text

        subroutine perturb_buffer_dummy(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``dummy`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_epstein_nesbet

    .. code:: text

        subroutine perturb_buffer_epstein_nesbet(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``epstein_nesbet`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_epstein_nesbet_2x2

    .. code:: text

        subroutine perturb_buffer_epstein_nesbet_2x2(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``epstein_nesbet_2x2`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_epstein_nesbet_2x2_no_ci_diag

    .. code:: text

        subroutine perturb_buffer_epstein_nesbet_2x2_no_ci_diag(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``epstein_nesbet_2x2_no_ci_diag`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_epstein_nesbet_sc2

    .. code:: text

        subroutine perturb_buffer_epstein_nesbet_sc2(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``epstein_nesbet_sc2`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_epstein_nesbet_sc2_no_projected

    .. code:: text

        subroutine perturb_buffer_epstein_nesbet_sc2_no_projected(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``epstein_nesbet_sc2_no_projected`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_epstein_nesbet_sc2_projected

    .. code:: text

        subroutine perturb_buffer_epstein_nesbet_sc2_projected(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``epstein_nesbet_sc2_projected`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_h_core

    .. code:: text

        subroutine perturb_buffer_h_core(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``h_core`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_moller_plesset

    .. code:: text

        subroutine perturb_buffer_moller_plesset(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``moller_plesset`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_moller_plesset_general

    .. code:: text

        subroutine perturb_buffer_moller_plesset_general(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``moller_plesset_general`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: perturb_buffer_qdpt

    .. code:: text

        subroutine perturb_buffer_qdpt(i_generator,buffer,buffer_size,e_2_pert_buffer,coef_pert_buffer,sum_e_2_pert,sum_norm_pert,sum_H_pert_diag,N_st,Nint,key_mask,fock_diag_tmp,electronic_energy)

    File: :file:`perturbation.irp.f_shell_13`

    Applly pertubration ``qdpt`` to the buffer of determinants generated in the H_apply routine.





.. c:function:: pt2_decontracted

    .. code:: text

        subroutine pt2_decontracted (electronic_energy,det_ref,det_pert,fock_diag_tmp,c_pert,e_2_pert,H_pert_diag,Nint,ndet,N_st,minilist,idx_minilist,N_minilist)

    File: :file:`pt2_equations.irp.f_template_606`

    





.. c:function:: pt2_dummy

    .. code:: text

        subroutine pt2_dummy (electronic_energy,det_ref,det_pert,fock_diag_tmp,c_pert,e_2_pert,H_pert_diag,Nint,ndet,N_st,minilist,idx_minilist,N_minilist)

    File: :file:`pt2_equations.irp.f_template_606`

    Dummy perturbation to add all connected determinants.





.. c:function:: pt2_epstein_nesbet

    .. code:: text

        subroutine pt2_epstein_nesbet (electronic_energy,det_ref,det_pert,fock_diag_tmp,c_pert,e_2_pert,H_pert_diag,Nint,ndet,N_st,minilist,idx_minilist,N_minilist)

    File: :file:`pt2_equations.irp.f_template_606`

    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> ) 






.. c:function:: pt2_epstein_nesbet_2x2

    .. code:: text

        subroutine pt2_epstein_nesbet_2x2 (electronic_energy,det_ref,det_pert,fock_diag_tmp,c_pert,e_2_pert,H_pert_diag,Nint,ndet,N_st,minilist,idx_minilist,N_minilist)

    File: :file:`pt2_equations.irp.f_template_606`

    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> 






.. c:function:: pt2_epstein_nesbet_2x2_no_ci_diag

    .. code:: text

        subroutine pt2_epstein_nesbet_2x2_no_ci_diag(electronic_energy,det_ref,det_pert,fock_diag_tmp,c_pert,e_2_pert,H_pert_diag,Nint,ndet,N_st,minilist,idx_minilist,N_minilist)

    File: :file:`pt2_equations.irp.f_template_606`

    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> 






.. c:function:: pt2_epstein_nesbet_sc2

    .. code:: text

        subroutine pt2_epstein_nesbet_sc2 (electronic_energy,det_ref,det_pert,fock_diag_tmp,c_pert,e_2_pert,H_pert_diag,Nint,ndet,N_st,minilist,idx_minilist,N_minilist)

    File: :file:`pt2_equations.irp.f_template_606`

    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> ) 






.. c:function:: pt2_epstein_nesbet_sc2_no_projected

    .. code:: text

        subroutine pt2_epstein_nesbet_SC2_no_projected (electronic_energy,det_ref,det_pert,fock_diag_tmp,c_pert,e_2_pert,H_pert_diag,Nint,ndet,N_st,minilist,idx_minilist,N_minilist)

    File: :file:`pt2_equations.irp.f_template_606`

    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 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





.. c:function:: pt2_epstein_nesbet_sc2_projected

    .. code:: text

        subroutine pt2_epstein_nesbet_SC2_projected (electronic_energy,det_ref,det_pert,fock_diag_tmp,c_pert,e_2_pert,H_pert_diag,Nint,ndet,N_st,minilist,idx_minilist,N_minilist)

    File: :file:`pt2_equations.irp.f_template_606`

    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 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





.. c:function:: pt2_h_core

    .. code:: text

        subroutine pt2_h_core(det_pert,c_pert,e_2_pert,H_pert_diag,Nint,ndet,N_st,minilist,idx_minilist,N_minilist)

    File: :file:`pert_single.irp.f`

    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> ) 






.. c:function:: pt2_moller_plesset

    .. code:: text

        subroutine pt2_moller_plesset (electronic_energy,det_ref,det_pert,fock_diag_tmp,c_pert,e_2_pert,H_pert_diag,Nint,ndet,N_st,minilist,idx_minilist,N_minilist)

    File: :file:`pt2_equations.irp.f_template_606`

    compute the standard Moller-Plesset perturbative first order coefficient and second order energetic contribution 
    for the various n_st states. 
    c_pert(i) = <psi(i)|H|det_pert>/(difference of orbital energies) 
    e_2_pert(i) = <psi(i)|H|det_pert>^2/(difference of orbital energies) 






.. c:function:: pt2_moller_plesset_general

    .. code:: text

        subroutine pt2_moller_plesset_general (electronic_energy,det_ref,det_pert,fock_diag_tmp,c_pert,e_2_pert,H_pert_diag,Nint,ndet,N_st,minilist,idx_minilist,N_minilist)

    File: :file:`pt2_equations.irp.f_template_606`

    compute the general Moller-Plesset perturbative first order coefficient and second order energetic contribution 
    for the various n_st states. 
    c_pert(i) = <psi(i)|H|det_pert>/(difference of orbital energies) 
    e_2_pert(i) = <psi(i)|H|det_pert>^2/(difference of orbital energies) 






.. c:function:: pt2_qdpt

    .. code:: text

        subroutine pt2_qdpt (electronic_energy,det_ref,det_pert,fock_diag_tmp,c_pert,e_2_pert,H_pert_diag,Nint,ndet,N_st,minilist,idx_minilist,N_minilist)

    File: :file:`pt2_equations.irp.f_template_606`

    compute the QDPT first order coefficient and second order energetic contribution 
    for the various N_st states. 
    c_pert(i) = <psi(i)|H|det_pert>/( <psi(i)|H|psi(i)> - <det_pert|H|det_pert> ) 






.. c:function:: remove_small_contributions

    .. code:: text

        subroutine remove_small_contributions

    File: :file:`selection.irp.f`

    Remove determinants with small contributions. N_states is assumed to be provided.





.. c:function:: repeat_all_e_corr

    .. code:: text

        double precision function repeat_all_e_corr(key_in)

    File: :file:`pert_sc2.irp.f`