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quantum_package/src/Perturbation/README.rst

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===================
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 <det_pert|Hi>
N_st
Number of states
Assumptions
===========
.. Do not edit this section. It was auto-generated from the
.. NEEDED_MODULES file.
* This is not allowed:
subroutine &
pt2_....
Documentation
=============
.. Do not edit this section. It was auto-generated from the
.. NEEDED_MODULES file.
`pt2_moller_plesset <http://github.com/LCPQ/quantum_package/tree/master/src/Perturbation/Moller_plesset.irp.f#L1>`_
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) = <psi(i)|H|det_pert>/(difference of orbital energies)
.br
e_2_pert(i) = <psi(i)|H|det_pert>^2/(difference of orbital energies)
.br
`pt2_epstein_nesbet <http://github.com/LCPQ/quantum_package/tree/master/src/Perturbation/epstein_nesbet.irp.f#L1>`_
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) = <psi(i)|H|det_pert>/( E(i) - <det_pert|H|det_pert> )
.br
e_2_pert(i) = <psi(i)|H|det_pert>^2/( E(i) - <det_pert|H|det_pert> )
.br
`pt2_epstein_nesbet_2x2 <http://github.com/LCPQ/quantum_package/tree/master/src/Perturbation/epstein_nesbet.irp.f#L43>`_
compute the Epstein-Nesbet 2x2 diagonalization coefficient and energetic contribution
.br
for the various N_st states.
.br
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 )
.br
c_pert(i) = e_2_pert(i)/ <psi(i)|H|det_pert>
.br
`pt2_epstein_nesbet_sc2_projected <http://github.com/LCPQ/quantum_package/tree/master/src/Perturbation/pert_sc2.irp.f#L2>`_
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 = <psi_i|H|det_pert>^2/(Delta_E)
.br
and also the purely projected contribution
.br
H_pert_diag = <HF|H|det_pert> c_pert
`repeat_all_e_corr <http://github.com/LCPQ/quantum_package/tree/master/src/Perturbation/pert_sc2.irp.f#L90>`_
Undocumented
`fill_h_apply_buffer_selection <http://github.com/LCPQ/quantum_package/tree/master/src/Perturbation/selection.irp.f#L1>`_
Fill the H_apply buffer with determiants for the selection
`remove_small_contributions <http://github.com/LCPQ/quantum_package/tree/master/src/Perturbation/selection.irp.f#L84>`_
Remove determinants with small contributions. N_states is assumed to be
provided.
`selection_criterion <http://github.com/LCPQ/quantum_package/tree/master/src/Perturbation/selection.irp.f#L71>`_
Threshold to select determinants. Set by selection routines.
`selection_criterion_factor <http://github.com/LCPQ/quantum_package/tree/master/src/Perturbation/selection.irp.f#L73>`_
Threshold to select determinants. Set by selection routines.
`selection_criterion_min <http://github.com/LCPQ/quantum_package/tree/master/src/Perturbation/selection.irp.f#L72>`_
Threshold to select determinants. Set by selection routines.
Needed Modules
==============
.. Do not edit this section. It was auto-generated from the
.. NEEDED_MODULES file.
* `AOs <http://github.com/LCPQ/quantum_package/tree/master/src/AOs>`_
* `BiInts <http://github.com/LCPQ/quantum_package/tree/master/src/BiInts>`_
* `Bitmask <http://github.com/LCPQ/quantum_package/tree/master/src/Bitmask>`_
* `Dets <http://github.com/LCPQ/quantum_package/tree/master/src/Dets>`_
* `Electrons <http://github.com/LCPQ/quantum_package/tree/master/src/Electrons>`_
* `Ezfio_files <http://github.com/LCPQ/quantum_package/tree/master/src/Ezfio_files>`_
* `Hartree_Fock <http://github.com/LCPQ/quantum_package/tree/master/src/Hartree_Fock>`_
* `MonoInts <http://github.com/LCPQ/quantum_package/tree/master/src/MonoInts>`_
* `MOs <http://github.com/LCPQ/quantum_package/tree/master/src/MOs>`_
* `Nuclei <http://github.com/LCPQ/quantum_package/tree/master/src/Nuclei>`_
* `Output <http://github.com/LCPQ/quantum_package/tree/master/src/Output>`_
* `Utils <http://github.com/LCPQ/quantum_package/tree/master/src/Utils>`_
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