quantum_package/src/Dets

===========
Dets Module
===========

This module contains the determinants of the CI wave function.

H is applied on the list of generator determinants. Selected determinants
are added into the *H_apply buffer*. Then the new wave function is
constructred as the concatenation of the odl wave function and
some determinants of the H_apply buffer. Generator determinants are built
as a subset of the determinants of the wave function.


Assumptions
===========

.. Do not edit this section. It was auto-generated from the
.. NEEDED_MODULES file.

* The MOs are orthonormal
* All the determinants have the same number of electrons
* The determinants are orthonormal
* The number of generator determinants <= the number of determinants
* All the determinants in the H_apply buffer are supposed to be different from the 
  wave function determinants
* All the determinants in the H_apply buffer are supposed to be unique


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>`_
* `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>`_

Documentation
=============

.. Do not edit this section. It was auto-generated from the
.. NEEDED_MODULES file.

`copy_h_apply_buffer_to_wf <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/H_apply.irp.f#L/subroutine copy_H_apply_buffer_to_wf/;">`_
  Undocumented

`h_apply_buffer_coef <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/H_apply.irp.f#L/&BEGIN_PROVIDER [ double precision, H_apply_buffer_coef,(H_apply_buffer_size,N_states) ]/;">`_
  Buffer of determinants/coefficients/perturbative energy for H_apply.
  Uninitialized. Filled by H_apply subroutines.

`h_apply_buffer_det <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/H_apply.irp.f#L/BEGIN_PROVIDER [ integer(bit_kind), H_apply_buffer_det,(N_int,2,H_apply_buffer_size) ]/;">`_
  Buffer of determinants/coefficients/perturbative energy for H_apply.
  Uninitialized. Filled by H_apply subroutines.

`h_apply_buffer_e2 <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/H_apply.irp.f#L/&BEGIN_PROVIDER [ double precision, H_apply_buffer_e2,(H_apply_buffer_size,N_states) ]/;">`_
  Buffer of determinants/coefficients/perturbative energy for H_apply.
  Uninitialized. Filled by H_apply subroutines.

`h_apply_buffer_n_det <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/H_apply.irp.f#L/&BEGIN_PROVIDER [ integer, H_apply_buffer_N_det ]/;">`_
  Buffer of determinants/coefficients/perturbative energy for H_apply.
  Uninitialized. Filled by H_apply subroutines.

`h_apply_buffer_size <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/H_apply.irp.f#L/BEGIN_PROVIDER [ integer*8, H_apply_buffer_size ]/;">`_
  Size of the H_apply buffer.

`h_apply_threshold <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/H_apply.irp.f#L/BEGIN_PROVIDER [ double precision, H_apply_threshold ]/;">`_
  Theshold on | <Di|H|Dj> |

`resize_h_apply_buffer_det <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/H_apply.irp.f#L/subroutine resize_H_apply_buffer_det(new_size)/;">`_
  Undocumented

`connected_to_ref <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/connected_to_ref.irp.f#L/integer function connected_to_ref(key,keys,Nint,N_past_in,Ndet,thresh)/;">`_
  Undocumented

`det_is_not_or_may_be_in_ref <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/connected_to_ref.irp.f#L/logical function det_is_not_or_may_be_in_ref(key,Nint)/;">`_
  If true, det is not in ref
  If false, det may be in ref

`key_pattern_not_in_ref <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/connected_to_ref.irp.f#L/BEGIN_PROVIDER [ logical, key_pattern_not_in_ref, (-128:127,N_int,2) ]/;">`_
  Min and max values of the integers of the keys of the reference

`davidson_diag <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/davidson.irp.f#L/subroutine davidson_diag(dets_in,u_in,energies,dim_in,sze,N_st,Nint)/;">`_
  Davidson diagonalization.
  .br
  dets_in : bitmasks corresponding to determinants
  .br
  u_in : guess coefficients on the various states. Overwritten
  on exit
  .br
  dim_in : leftmost dimension of u_in
  .br
  sze : Number of determinants
  .br
  N_st : Number of eigenstates
  .br
  Initial guess vectors are not necessarily orthonormal

`davidson_iter_max <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/davidson.irp.f#L/BEGIN_PROVIDER [ integer, davidson_iter_max]/;">`_
  Max number of Davidson iterations

`davidson_sze_max <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/davidson.irp.f#L/BEGIN_PROVIDER [ integer, davidson_sze_max]/;">`_
  Max number of Davidson sizes

`n_det <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/determinants.irp.f#L/BEGIN_PROVIDER [ integer, N_det ]/;">`_
  Number of determinants in the wave function

`n_det_generators <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/determinants.irp.f#L/BEGIN_PROVIDER [ integer, N_det_generators ]/;">`_
  Number of generator determinants in the wave function

`n_states <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/determinants.irp.f#L/BEGIN_PROVIDER [ integer, N_states ]/;">`_
  Number of states to consider

`psi_coef <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/determinants.irp.f#L/&BEGIN_PROVIDER [ double precision, psi_coef, (psi_det_size,N_states) ]/;">`_
  The wave function. Initialized with Hartree-Fock

`psi_det <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/determinants.irp.f#L/BEGIN_PROVIDER [ integer(bit_kind), psi_det, (N_int,2,psi_det_size) ]/;">`_
  The wave function. Initialized with Hartree-Fock

`psi_det_size <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/determinants.irp.f#L/BEGIN_PROVIDER [ integer, psi_det_size ]/;">`_
  Size of the psi_det/psi_coef arrays

`psi_generators <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/determinants.irp.f#L/BEGIN_PROVIDER [ integer(bit_kind), psi_generators, (N_int,2,psi_det_size) ]/;">`_
  Determinants on which H is applied

`psi_ref <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/determinants.irp.f#L/BEGIN_PROVIDER [ integer(bit_kind), psi_ref, (N_int,2,psi_ref_size) ]/;">`_
  Determinants on which H is applied

`psi_ref_coef <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/determinants.irp.f#L/&BEGIN_PROVIDER [ double precision, psi_ref_coef, (psi_ref_size,N_states) ]/;">`_
  Determinants on which H is applied

`psi_ref_size <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/determinants.irp.f#L/BEGIN_PROVIDER [ integer, psi_ref_size]/;">`_
  Number of generator determinants in the wave function

`double_exc_bitmask <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/determinants_bitmasks.irp.f#L/BEGIN_PROVIDER [ integer(bit_kind), double_exc_bitmask, (N_int, 4, N_double_exc_bitmasks) ]/;">`_
  double_exc_bitmask(:,1,i) is the bitmask for holes of excitation 1
  double_exc_bitmask(:,2,i) is the bitmask for particles of excitation 1
  double_exc_bitmask(:,3,i) is the bitmask for holes of excitation 2
  double_exc_bitmask(:,4,i) is the bitmask for particles of excitation 2
  for a given couple of hole/particle excitations i.

`n_double_exc_bitmasks <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/determinants_bitmasks.irp.f#L/BEGIN_PROVIDER [ integer, N_double_exc_bitmasks ]/;">`_
  Number of double excitation bitmasks

`n_single_exc_bitmasks <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/determinants_bitmasks.irp.f#L/BEGIN_PROVIDER [ integer, N_single_exc_bitmasks ]/;">`_
  Number of single excitation bitmasks

`single_exc_bitmask <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/determinants_bitmasks.irp.f#L/BEGIN_PROVIDER [ integer(bit_kind), single_exc_bitmask, (N_int, 2, N_single_exc_bitmasks) ]/;">`_
  single_exc_bitmask(:,1,i) is the bitmask for holes
  single_exc_bitmask(:,2,i) is the bitmask for particles
  for a given couple of hole/particle excitations i.

`filter_connected <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/filter_connected.irp.f#L/subroutine filter_connected(key1,key2,Nint,sze,idx)/;">`_
  Filters out the determinants that are not connected by H
  .br
  returns the array idx which contains the index of the
  .br
  determinants in the array key1 that interact
  .br
  via the H operator with key2.
  .br
  idx(0) is the number of determinants that interact with key1

`filter_connected_i_h_psi0 <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/filter_connected.irp.f#L/subroutine filter_connected_i_H_psi0(key1,key2,Nint,sze,idx)/;">`_
  returns the array idx which contains the index of the
  .br
  determinants in the array key1 that interact
  .br
  via the H operator with key2.
  .br
  idx(0) is the number of determinants that interact with key1

`filter_connected_i_h_psi0_sc2 <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/filter_connected.irp.f#L/subroutine filter_connected_i_H_psi0_SC2(key1,key2,Nint,sze,idx,idx_repeat)/;">`_
  standard filter_connected_i_H_psi but returns in addition
  .br
  the array of the index of the non connected determinants to key1
  .br
  in order to know what double excitation can be repeated on key1
  .br
  idx_repeat(0) is the number of determinants that can be used
  .br
  to repeat the excitations

`get_s2 <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/s2.irp.f#L/subroutine get_s2(key_i,key_j,phase,Nint)/;">`_
  Returns <S^2>

`get_s2_u0 <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/s2.irp.f#L/subroutine get_s2_u0(psi_keys_tmp,psi_coefs_tmp,n,nmax,s2)/;">`_
  Undocumented

`s_z <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/s2.irp.f#L/BEGIN_PROVIDER [ double precision, S_z ]/;">`_
  Undocumented

`s_z2_sz <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/s2.irp.f#L/&BEGIN_PROVIDER [ double precision, S_z2_Sz ]/;">`_
  Undocumented

`a_operator <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/slater_rules.irp.f#L/subroutine a_operator(iorb,ispin,key,hjj,Nint,na,nb)/;">`_
  Needed for diag_H_mat_elem

`ac_operator <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/slater_rules.irp.f#L/subroutine ac_operator(iorb,ispin,key,hjj,Nint,na,nb)/;">`_
  Needed for diag_H_mat_elem

`decode_exc <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/slater_rules.irp.f#L/subroutine decode_exc(exc,degree,h1,p1,h2,p2,s1,s2)/;">`_
  Decodes the exc arrays returned by get_excitation.
  h1,h2 : Holes
  p1,p2 : Particles
  s1,s2 : Spins (1:alpha, 2:beta)
  degree : Degree of excitation

`diag_h_mat_elem <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/slater_rules.irp.f#L/double precision function diag_H_mat_elem(det_in,Nint)/;">`_
  Computes <i|H|i>

`get_double_excitation <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/slater_rules.irp.f#L/subroutine get_double_excitation(det1,det2,exc,phase,Nint)/;">`_
  Returns the two excitation operators between two doubly excited determinants and the phase

`get_excitation <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/slater_rules.irp.f#L/subroutine get_excitation(det1,det2,exc,degree,phase,Nint)/;">`_
  Returns the excitation operators between two determinants and the phase

`get_excitation_degree <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/slater_rules.irp.f#L/subroutine get_excitation_degree(key1,key2,degree,Nint)/;">`_
  Returns the excitation degree between two determinants

`get_excitation_degree_vector <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/slater_rules.irp.f#L/subroutine get_excitation_degree_vector(key1,key2,degree,Nint,sze,idx)/;">`_
  Applies get_excitation_degree to an array of determinants

`get_mono_excitation <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/slater_rules.irp.f#L/subroutine get_mono_excitation(det1,det2,exc,phase,Nint)/;">`_
  Returns the excitation operator between two singly excited determinants and the phase

`get_occ_from_key <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/slater_rules.irp.f#L/subroutine get_occ_from_key(key,occ,Nint)/;">`_
  Returns a list of occupation numbers from a bitstring

`h_u_0 <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/slater_rules.irp.f#L/subroutine H_u_0(v_0,u_0,H_jj,n,keys_tmp,Nint)/;">`_
  Computes v_0 = H|u_0>
  .br
  n : number of determinants
  .br
  H_jj : array of <j|H|j>

`i_h_j <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/slater_rules.irp.f#L/subroutine i_H_j(key_i,key_j,Nint,hij)/;">`_
  Returns <i|H|j> where i and j are determinants

`i_h_psi <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/slater_rules.irp.f#L/subroutine i_H_psi(key,keys,coef,Nint,Ndet,Ndet_max,Nstate,i_H_psi_array)/;">`_
  <key|H|psi> for the various Nstate

`i_h_psi_sc2 <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/slater_rules.irp.f#L/subroutine i_H_psi_SC2(key,keys,coef,Nint,Ndet,Ndet_max,Nstate,i_H_psi_array,idx_repeat)/;">`_
  <key|H|psi> for the various Nstate
  .br
  returns in addition
  .br
  the array of the index of the non connected determinants to key1
  .br
  in order to know what double excitation can be repeated on key1
  .br
  idx_repeat(0) is the number of determinants that can be used
  .br
  to repeat the excitations

`h_matrix_all_dets <http://github.com/LCPQ/quantum_package/tree/master/src/Dets/utils.irp.f#L/BEGIN_PROVIDER [ double precision, H_matrix_all_dets,(n_det,n_det) ]/;">`_
  H matrix on the basis of the slater deter;inants defined by psi_det