sigma_cda_uks.h

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/*
 *            Copyright 2009-2020 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.
 *
 */
 
#pragma once
#ifndef VOTCA_XTP_SIGMA_CDA_UKS_H
#define VOTCA_XTP_SIGMA_CDA_UKS_H
 
#include "votca/xtp/ImaginaryAxisIntegration.h"
#include "votca/xtp/logger.h"
#include "votca/xtp/rpa_uks.h"
#include "votca/xtp/sigma_base_uks.h"
#include <complex>
 
namespace votca {
namespace xtp {
 
class Sigma_CDA_UKS : public Sigma_base_UKS {
 public:
  Sigma_CDA_UKS(TCMatrix_gwbse_spin& Mmn, RPA_UKS& rpa,
                TCMatrix::SpinChannel spin)
      : Sigma_base_UKS(Mmn, rpa, spin),
        gq_(getSpinRPAInputEnergies(), Mmn[spin]) {}
 
  ~Sigma_CDA_UKS() override = default;
 
  void PrepareScreening() final;
 
  double CalcCorrelationDiagElement(Index gw_level,
                                    double frequency) const final;
 
  double CalcCorrelationDiagElementDerivative(Index gw_level,
                                              double frequency) const final {
    double h = 1e-3;
    double plus = CalcCorrelationDiagElement(gw_level, frequency + h);
    double minus = CalcCorrelationDiagElement(gw_level, frequency - h);
    return (plus - minus) / (2 * h);
  }
 
  // Off-diagonal elements are not implemented for CDA: zero
  double CalcCorrelationOffDiagElement(Index, Index, double,
                                       double) const final {
    return 0.0;
  }
  bool HasOffDiagonal() const final { return false; }
 
 private:
  double CalcResiduePrefactor(double e_f, double e_m, double frequency) const;
  double CalcResidueContribution(double frequency, Index gw_level) const;
  double CalcDiagContribution(const Eigen::MatrixXd::ConstRowXpr& Imx_row,
                              double delta, double eta) const;
  // Imx_row kappa(0) Imx_row^T is tail_terms_[gw_level](i)
  double CalcDiagContributionValue_tail(double row_term, double delta,
                                        double alpha) const;
 
  ImaginaryAxisIntegration gq_;
  Eigen::MatrixXd kDielMxInv_zero_;
  // per GW level: Imx.row(i) kappa(0) Imx.row(i)^T for every level i
  std::vector<Eigen::VectorXd> tail_terms_;
};
 
}  // namespace xtp
}  // namespace votca
 
#endif