dftgradient.h

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/*
 *            Copyright 2009-2024 The VOTCA Development Team
 *                       (http://www.votca.org)
 *
 *      Licensed under the Apache License, Version 2.0 (the "License")
 *
 * You may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *              http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */
 
// ===========================================================================
// STATUS: new, in-progress home for DFT gradient (nuclear force) assembly,
// as distinct from the raw integral derivatives in libint2_derivative_calls
// (which this consumes). Currently implements ONLY the nuclear repulsion
// term. Not yet wired into DFTEngine or Orbitals::setForces() -- that is
// a separate, later step once the RI-J (and, if hybrids matter, RI-K) and
// XC gradient terms exist alongside this one.
//
// Planned eventual contents, per the dependency order worked out
// separately: nuclear repulsion (this commit) -> RI-J gradient assembly,
// contracting the already-validated two-/three-center integral
// derivatives with the converged density and fitting coefficients ->
// XC gradient (density-derivative + SSW grid-weight-derivative terms,
// the one piece with no existing shortcut in the codebase) -> total
// gradient, called from DFTEngine once SCF has converged, written to
// Orbitals::setForces(). CDFT's own lambda_i * d(w_i)/dR term rides on
// the XC term's grid-weight-derivative code, once that exists, and is
// deliberately out of scope until the plain-DFT case is complete and
// tested end to end.
// ===========================================================================
 
#pragma once
#ifndef VOTCA_XTP_DFTGRADIENT_H
#define VOTCA_XTP_DFTGRADIENT_H
 
// Local VOTCA includes
#include "aobasis.h"
#include "qmmolecule.h"
 
namespace votca {
namespace xtp {
 
class DFTGradient {
 public:
  static Eigen::MatrixXd NuclearRepulsionDerivative(const QMMolecule& mol);

  static Eigen::MatrixXd RIJGradient(const Eigen::MatrixXd& density,
                                     const AOBasis& auxbasis,
                                     const AOBasis& dftbasis);

  static Eigen::MatrixXd RIKGradient(const Eigen::MatrixXd& occ_mo_coeffs,
                                     const AOBasis& auxbasis,
                                     const AOBasis& dftbasis);
};
 
}  // namespace xtp
}  // namespace votca
 
#endif  // VOTCA_XTP_DFTGRADIENT_H