AP1roGGeminalCoefficients.hpp

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// This file is part of GQCG-GQCP.
//
// Copyright (C) 2017-2020  the GQCG developers
//
// GQCG-GQCP 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, either version 3 of the License, or
// (at your option) any later version.
//
// GQCG-GQCP 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 GQCG-GQCP.  If not, see <http://www.gnu.org/licenses/>.
 
#pragma once
 
 
#include "Basis/SpinorBasis/OrbitalSpace.hpp"
#include "Mathematical/Representation/ImplicitMatrixSlice.hpp"
#include "Operator/SecondQuantized/SQHamiltonian.hpp"
#include "QCModel/CI/LinearExpansion.hpp"
#include "QCModel/Geminals/GeminalCoefficientsInterface.hpp"
 
 
namespace GQCP {
 
 
class AP1roGGeminalCoefficients: public GeminalCoefficientsInterface {
private:
    size_t K;                       // the number of spatial orbitals corresponding to these geminal coefficients
    size_t N_P;                     // the number of electron pairs (i.e. the number of geminals) corresponding to these geminal coefficients
    ImplicitMatrixSlice<double> G;  // the AP1roG geminal coefficients (not including the identity matrix on the left), as a block matrix, so it implements easy operator(i,a) calls
 
 
public:
    // CONSTRUCTORS
 
    AP1roGGeminalCoefficients(const ImplicitMatrixSlice<double>& G, const size_t N_P, const size_t K);
 
    AP1roGGeminalCoefficients(const MatrixX<double>& G);
 
    AP1roGGeminalCoefficients(const size_t N_P, const size_t K);
 
 
    // DESTRUCTOR
 
    ~AP1roGGeminalCoefficients() override;
 
 
    // OPERATORS
 
    double operator()(const size_t i, const size_t a) const;
 
 
    // NAMED CONSTRUCTORS
 
    static AP1roGGeminalCoefficients FromColumnMajor(const VectorX<double>& g, const size_t N_P, const size_t K);
 
    static AP1roGGeminalCoefficients FromRowMajor(const VectorX<double>& g, const size_t N_P, const size_t K);
 
    static AP1roGGeminalCoefficients WeakInteractionLimit(const RSQHamiltonian<double>& sq_hamiltonian, const size_t N_P);
 
 
    // STATIC PUBLIC METHODS
 
    static size_t numberOfGeminalCoefficients(const size_t N_P, const size_t K);
 
 
    // PUBLIC METHODS
 
    MatrixX<double> asMatrix() const;
 
    VectorX<double> asVector() const { return this->G.asVector(); }
 
    size_t count() const { return AP1roGGeminalCoefficients::numberOfGeminalCoefficients(this->N_P, this->K); }
 
    size_t numberOfElectronPairs() const { return this->N_P; }
 
    size_t numberOfSpatialOrbitals() const { return this->K; }
 
    OrbitalSpace orbitalSpace() const;
 
    double overlap(const SpinUnresolvedONV& onv) const override;
};
 
 
}  // namespace GQCP