From ce87a620868e43c1742b6c385705753db86ffd4f Mon Sep 17 00:00:00 2001
From: Kevin Gasperich <kgasperich@gmail.com>
Date: Wed, 19 Feb 2020 12:47:22 -0600
Subject: [PATCH] starting complex determinants

---
 src/determinants/create_excitations.irp.f | 27 ++++++++++++++++++++
 src/utils_complex/qp2-pbc-diff.txt        | 30 +++++++++++++++++++----
 2 files changed, 52 insertions(+), 5 deletions(-)

diff --git a/src/determinants/create_excitations.irp.f b/src/determinants/create_excitations.irp.f
index cec87901..f3b19afa 100644
--- a/src/determinants/create_excitations.irp.f
+++ b/src/determinants/create_excitations.irp.f
@@ -80,6 +80,33 @@ subroutine build_singly_excited_wavefunction(i_hole,i_particle,ispin,det_out,coe
   enddo
 end
 
+subroutine build_singly_excited_wavefunction_complex(i_hole,i_particle,ispin,det_out,coef_out)
+  implicit none
+  BEGIN_DOC
+  ! Applies the single excitation operator : a^{dager}_(i_particle) a_(i_hole) of
+  ! spin = ispin to the current wave function (psi_det, psi_coef)
+  END_DOC
+  integer, intent(in)            :: i_hole,i_particle,ispin
+  integer(bit_kind), intent(out) :: det_out(N_int,2,N_det)
+  complex*16, intent(out)  :: coef_out(N_det,N_states)
+
+  integer :: k
+  integer :: i_ok
+  double precision :: phase
+  do k=1,N_det
+    coef_out(k,:) = psi_coef(k,:)
+    det_out(:,:,k) = psi_det(:,:,k)
+    call do_single_excitation(det_out(1,1,k),i_hole,i_particle,ispin,i_ok)
+    if (i_ok == 1) then
+      call get_phase(psi_det(1,1,k), det_out(1,1,k),phase,N_int)
+      coef_out(k,:) = phase * coef_out(k,:)
+    else
+      coef_out(k,:) = (0.d0,0.d0)
+      det_out(:,:,k) = psi_det(:,:,k)
+    endif
+  enddo
+end
+
 logical function is_spin_flip_possible(key_in,i_flip,ispin)
   implicit none
   BEGIN_DOC
diff --git a/src/utils_complex/qp2-pbc-diff.txt b/src/utils_complex/qp2-pbc-diff.txt
index c0980e13..4e2cd568 100644
--- a/src/utils_complex/qp2-pbc-diff.txt
+++ b/src/utils_complex/qp2-pbc-diff.txt
@@ -1,10 +1,22 @@
 
+-------------------------------------------------------------------------------------
+current:
+
+determinants:
+  TODO
+    create_excitations
+      do_single_excitation
+        use symmetry rules to simplify?
+        should this be general, or should we only allow singles that conserve momentum?
+    density_matrix
+    ...
+
+  DONE
+    create_excitations
+      build_singly_excited_wavefunction{_complex}
+
 
-2e integrals printed from pyscf are in physicists' notation
-mo energies from pyscf include ewald correction; in qp we just fold that into the nuclear repulsion
-this may need to change for addition/removal of electrons (shift in enuc depends on number of electrons)
-
-
+-------------------------------------------------------------------------------------
 
 for complex data, add extra dim (size 2) and treat as real in EZFIO.cfg
 
@@ -34,6 +46,8 @@ translational symmetry:
   I + J = K + L
   kconserv(I,J,K)=L
 
+------------------------------------------------------------------------------
+
 TODO:
 symmetry
   restructure arrays?
@@ -71,6 +85,12 @@ later:
 
 
 NOTES:
+  2e integrals printed from pyscf are in physicists' notation
+  
+  mo energies from pyscf include ewald correction; in qp we just fold that into the nuclear repulsion
+    this may need to change for addition/removal of electrons
+      (shift in enuc depends on number of electrons)
+
   3-index integrals
     <ij|kl> = \sum_\mu (ik|\mu)(jl|\mu)
     store (ik|\mu) for I<=K