/*
 * @BEGIN LICENSE
 *
 * Psi4: an open-source quantum chemistry software package
 *
 * Copyright (c) 2007-2019 The Psi4 Developers.
 *
 * The copyrights for code used from other parties are included in
 * the corresponding files.
 *
 * This file is part of Psi4.
 *
 * Psi4 is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, version 3.
 *
 * Psi4 is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License along
 * with Psi4; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * @END LICENSE
 */

/*! \file
    \ingroup CCDENSITY
    \brief Enter brief description of file here
*/
#include "MOInfo.h"
#include "Params.h"
#include "Frozen.h"
#define EXTERN
#include "globals.h"

namespace psi {
namespace ccdensity {

/* DEANTI(): Convert the two-particle density from Dirac to Mulliken
** ordering.  The original, Fock-adjusted density (see the comments in
** fock.c) corresponds to a two-electron energy (or energy derivative)
** expression of the form:
**
** E(TWO) = 1/4 sum_pqrs Gpqrs <pq||rs>
**
** However, the derivative two-electron integrals are produced in
** Mulliken-ordered, symmetric form rather than Dirac-ordered
** antisymmetric form.  This code alters the two-particle density
** matrix ordering for the energy expression of the form:
**
** E(TWO) = 1/2 sum_pqrs Gpqrs <pq|rs>
**
** The final conversion to Mulliken ordering is taken care of in
** dump.c
**
** The second equation above may be derived via
**
** E(TWO) = 1/4 sum_pqrs Gpqrs (<pq|rs> - <pq|sr>)
**        = 1/4 sum_pqrs Gpqrs <pq|rs> - 1/4 sum_pqrs Gpqrs <pq|sr>
**        = 1/4 sum_pqrs Gpqrs <pq|rs> - 1/4 sum_pqrs Gpqsr <pq|rs>
**        = 1/4 sum_pqrs (Gpqrs - Gpqsr) <pq|rs>
**        = 1/2 sum_pqrs Gpqrs <pq|rs>
**
** Equations for the individual components are given explicitly in
** comments below.
** */

void deanti_RHF(struct RHO_Params rho_params);
void deanti_ROHF(struct RHO_Params rho_params);
void deanti_UHF(struct RHO_Params rho_params);

void deanti(struct RHO_Params rho_params) {
    if (params.ref == 0)
        deanti_RHF(rho_params);
    else if (params.ref == 1)
        deanti_ROHF(rho_params);
    else if (params.ref == 2)
        deanti_UHF(rho_params);
}

}  // namespace ccdensity
}  // namespace psi
