MatsubaraSusceptibilityCalculator.h

/* Copyright 2018 Kristofer Björnson
 *
 * 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.
 */
 
 
#ifndef COM_DAFER45_TBTK_MATSUBARA_SUSCEPTIBILITY_CALCULATOR
#define COM_DAFER45_TBTK_MATSUBARA_SUSCEPTIBILITY_CALCULATOR
 
#include "TBTK/RPA/SusceptibilityCalculator.h"
 
#include <complex>
 
//#include <omp.h>
 
namespace TBTK{
 
class MatsubaraSusceptibilityCalculator : public SusceptibilityCalculator{
public:
    MatsubaraSusceptibilityCalculator(
        const RPA::MomentumSpaceContext &momentumSpaceContext
    );
 
    ~MatsubaraSusceptibilityCalculator();
 
    MatsubaraSusceptibilityCalculator* createSlave();
 
    std::complex<double> calculateSusceptibility(
        const std::vector<double> &k,
        const std::vector<int> &orbitalIndices,
        std::complex<double> energy
    );
 
    std::vector<std::complex<double>> calculateSusceptibility(
        const DualIndex &kDual,
        const std::vector<int> &orbitalIndices
    );
 
    void setNumSummationEnergies(unsigned int numSummationEnergies);
private:
    std::complex<double> *greensFunction;
 
    std::vector<std::complex<double>> summationEnergies;
 
    MatsubaraSusceptibilityCalculator(
        const RPA::MomentumSpaceContext &momentumSpaceContext,
        int *kPlusQLookupTable
    );
 
    std::complex<double> calculateSusceptibilityMatsubara(
        const std::vector<double> &k,
        const std::vector<int> &orbitalIndices,
        std::complex<double> energy
    );
 
    template<bool useKPlusQLookupTable>
    std::vector<std::complex<double>> calculateSusceptibilityMatsubara(
        const DualIndex &kDual,
        const std::vector<int> &orbitalIndices
    );
 
    void calculateGreensFunction();
 
    std::complex<double>& getGreensFunctionValue(
        unsigned int meshPoint,
        unsigned int orbital0,
        unsigned int orbital1,
        unsigned int energy,
        unsigned int numEnergies,
        unsigned int numOrbitals
    );
};
 
inline void MatsubaraSusceptibilityCalculator::setNumSummationEnergies(
    unsigned int numSummationEnergies
){
    TBTKAssert(
        numSummationEnergies%2 == 1,
        "MatsubaraSusceptibilityCalculator::setNumSummationEnergies()",
        "The number of summation energies must be an odd number.",
        ""
    );
 
    double temperature
        = UnitHandler::convertNaturalToBase<Quantity::Temperature>(
            getMomentumSpaceContext().getModel().getTemperature()
        );
    double kT = UnitHandler::getConstantInBaseUnits("k_B")*temperature;
    double hbar = UnitHandler::getConstantInBaseUnits("hbar");
 
    summationEnergies.clear();
    for(unsigned int n = 0; n < numSummationEnergies; n++){
        summationEnergies.push_back(
            M_PI*(2*(n - numSummationEnergies/2))*kT/hbar
        );
    }
 
    clearCache();
    if(greensFunction != nullptr){
        delete [] greensFunction;
        greensFunction = nullptr;
    }
}
 
/*inline std::vector<std::complex<double>> SusceptibilityCalculator::calculateSusceptibility(
        const std::vector<double> &k,
        const std::vector<int> &orbitalIndices
){
    return calculateSusceptibility(
        DualIndex(
            momentumSpaceContext->getKIndex(k),
            k
        ),
        orbitalIndices
    );
}*/
 
inline std::complex<double>& MatsubaraSusceptibilityCalculator::getGreensFunctionValue(
    unsigned int meshPoint,
    unsigned int orbital0,
    unsigned int orbital1,
    unsigned int energy,
    unsigned int numEnergies,
    unsigned int numOrbitals
){
    return greensFunction[
        numEnergies*(
            numOrbitals*(numOrbitals*meshPoint + orbital0)
            + orbital1
        ) + energy
    ];
}
 
};  //End of namespace TBTK
 
#endif