ElectronScattering.h

/*-------------------------------------------------------------------
Copyright 2015 Ravishankar Sundararaman

This file is part of JDFTx.

JDFTx is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

JDFTx 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 General Public License for more details.

You should have received a copy of the GNU General Public License
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-------------------------------------------------------------------*/

#ifndef JDFTX_ELECTRONIC_ELECTRONSCATTERING_H
#define JDFTX_ELECTRONIC_ELECTRONSCATTERING_H

#include <electronic/common.h>
#include <electronic/Basis.h>
#include <electronic/ColumnBundle.h>
#include <core/LatticeUtils.h>
#include <vector>

struct ElectronScattering
{
        double eta; 
        double Ecut; 
        double fCut; 
        double omegaMax; 
        
        ElectronScattering();
        void dump(const Everything& e); 

private:
        const Everything* e;
        int nBands, nSpinor;
        double Emin, Emax; 
        std::vector<ColumnBundle> C; //wavefunctions, made available on all processes
        std::vector<diagMatrix> E, F; //energies and fillings, available on all processes
        std::shared_ptr<const Supercell> supercell; //contains transformations between full and reduced k-mesh
        std::shared_ptr<const PeriodicLookup< vector3<> > > plook; //O(1) lookup for finding k-points in mesh
        std::vector<QuantumNumber> qmesh; //reduced momentum-transfer mesh
        std::vector<Basis> basisChi; //polarizability bases for qmesh
        Basis basis; //common wavefunction  basis
        std::map< vector3<int>, std::shared_ptr<class ColumnBundleTransform> > transform; //k-mesh transformations
        std::map< vector3<int>, QuantumNumber > qnumMesh; //equivalent of eInfo.qnums for entire k-mesh
        
        struct Event
        {       int i, j; //band indices
                double fWeight; //relevant fillings combination ( (fi - fj)/2 or (1-fi-fj) for chiMode = true or false )
                double Eji; //Ej - Ei
        };
        
        struct CEDA
        {       diagMatrix Fsum, FEsum; 
                std::vector<diagMatrix> FNLsum; 
                std::vector<diagMatrix> oNum, oDen; 
                
                CEDA(int nBands, int nbasis); 
                void collect(const ElectronScattering& es, int iq, const diagMatrix& chiKS0, diagMatrix& num, diagMatrix& den); 
        };
        friend struct CEDA;
        
        std::vector<Event> getEvents( 
                bool chiMode, 
                size_t ik, 
                size_t iq, 
                size_t& jk, 
                matrix& nij, 
                CEDA* ceda = 0 
        ) const;
        
        ColumnBundle getWfns(size_t ik, const vector3<>& k) const; //get wavefunctions at an arbitrary point in k-mesh
        matrix coulombMatrix(size_t iq) const; //retrieve the Coulomb operator for a specific momentum transfer
};

#endif //JDFTX_ELECTRONIC_ELECTRONSCATTERING_H