nemo.h

Go to the documentation of this file.

/*
 This file is part of MADNESS.
 
 Copyright (C) 2007,2010 Oak Ridge National Laboratory
 
 This program 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 2 of the License, or
 (at your option) any later version.
 
 This program 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
 along with this program; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 
 For more information please contact:
 
 Robert J. Harrison
 Oak Ridge National Laboratory
 One Bethel Valley Road
 P.O. Box 2008, MS-6367
 
 email: harrisonrj@ornl.gov
 tel:   865-241-3937
 fax:   865-572-0680
 */
 
/*!
 \file examples/nemo.h
 \brief solve the HF equations using numerical exponential MOs
 
 The source is
 <a href=http://code.google.com/p/m-a-d-n-e-s-s/source/browse/local
 /trunk/src/apps/examples/nemo.h>here</a>.
 
 */
 
#ifndef NEMO_H_
#define NEMO_H_
 
#include <madness/mra/mra.h>
#include <madness/mra/funcplot.h>
#include <madness/mra/operator.h>
#include <madness/mra/lbdeux.h>
#include<madness/chem/SCF.h>
#include<madness/chem/CalculationParameters.h>
#include<madness/chem/SCFProtocol.h>
#include<madness/chem/correlationfactor.h>
#include<madness/chem/molecular_optimizer.h>
#include <madness/mra/nonlinsol.h>
#include <madness/mra/vmra.h>
#include<madness/chem/pcm.h>
#include<madness/chem/AC.h>
#include<madness/chem/pointgroupsymmetry.h>
#include "Results.h"
#include"madness/mra/commandlineparser.h"
#include<madness/chem/QCPropertyInterface.h>
#include <madness/world/timing_utilities.h>
 
namespace madness {
 
class PNO;
class OEP;
 
 
class NemoBase : public MolecularOptimizationTargetInterface {
 
public:
 
    explicit NemoBase(World& w) : world(w) {}
 
    virtual ~NemoBase() {}
 
    virtual std::shared_ptr<Fock<double,3>> make_fock_operator() const {
        MADNESS_EXCEPTION("implement make_fock operator for your derived NemoBase class",1);
        return std::shared_ptr<Fock<double,3>>();
    }
 
        /// create an instance of the derived object based on the input parameters
    std::shared_ptr<NuclearCorrelationFactor> get_ncf_ptr() const {
        return ncf;
    }
 
    /// normalize the nemos
    template<typename T, std::size_t NDIM>
    void static normalize(std::vector<Function<T,NDIM> >& nemo,
            const Function<double,NDIM> metric=Function<double,NDIM>()) {
 
        if (nemo.size()==0) return;
        World& world=nemo[0].world();
        // compute the norm of the reconstructed orbitals, includes the factor
        std::vector<Function<T,NDIM> > mos = (metric.is_initialized()) ? metric*nemo : nemo;
        std::vector<double> norms = norm2s(world, mos);
 
        // scale the nemos, excludes the nuclear correlation factor
        std::vector<double> invnorm(norms.size());
        for (std::size_t i = 0; i < norms.size(); ++i)
            invnorm[i] = 1.0 / norms[i];
        scale(world, nemo, invnorm);
    }
 
    /// reproject a set of nemos onto the current k and thresh
 
    /// The counterpart of SCF::project (chem/SCF.cc) for regularized orbitals.
    /// SCF::project must NOT be used here: it normalizes with the plain L2
    /// metric, while nemos are normalized against R^2. Without this, a protocol
    /// step that changes k leaves the nemos at the old polynomial order while
    /// FunctionDefaults, R and the potentials have already moved to the new one.
    template<typename T, std::size_t NDIM>
    void reproject_mos(std::vector<Function<T,NDIM> >& nemo,
            const Function<double,NDIM>& metric) const {
 
        if (nemo.size()==0) return;
        const int k=FunctionDefaults<NDIM>::get_k();
        const double thresh=FunctionDefaults<NDIM>::get_thresh();
        if (nemo.front().k()==k) {           // nothing to do but retighten
            set_thresh(world,nemo,thresh);
            return;
        }
 
        if (world.rank()==0) print("reprojecting nemos from k =",nemo.front().k(),"to k =",k);
        reconstruct(world,nemo);
        for (std::size_t i=0; i<nemo.size(); ++i)
            nemo[i]=madness::project(nemo[i],k,thresh,false);
        world.gop.fence();
        truncate(world,nemo);
        normalize(nemo,metric);
    }
 
    template<typename T>
    static Tensor<T> Q2(const Tensor<T>& s) {
        Tensor<T> Q = -0.5*s;
        for (int i=0; i<s.dim(0); ++i) Q(i,i) += 1.5;
        return Q;
    }
 
    /// orthonormalize the vectors
    template<typename T, std::size_t NDIM>
    void orthonormalize(std::vector<Function<T,NDIM> >& nemo,
            const Function<double,NDIM> metric=Function<double,NDIM>(),
            const double trantol=FunctionDefaults<NDIM>::get_thresh()*0.01) const {
 
        if (nemo.size()==0) return;
        normalize(nemo,metric);
        double maxq;
        do {
            std::vector<Function<T,NDIM> > Rnemo = (metric.is_initialized()) ? metric*nemo : nemo;
            Tensor<T> Q = Q2(matrix_inner(world, Rnemo, Rnemo));
            maxq=0.0;
            for (int i=0; i<Q.dim(0); ++i)
                for (int j=0; j<i; ++j)
                    maxq = std::max(maxq,std::abs(Q(i,j)));
 
            Q.screen(trantol); // ???? Is this really needed?
            nemo = transform(world, nemo, Q, trantol, true);
            truncate(world, nemo);
//          if (world.rank() == 0) print("ORTHOG2: maxq trantol", maxq, trantol);
 
        } while (maxq>0.01);
        normalize(nemo,metric);
    }
 
    template<typename T, std::size_t NDIM>
    Function<typename Tensor<T>::scalar_type,NDIM> compute_density(const std::vector<Function<T,NDIM> > nemo) const {
        return sum(world,abssq(world,nemo)).truncate();
    }
 
    virtual bool need_recompute_factors_and_potentials(const double thresh) const {
        bool need=false;
        const int k=FunctionDefaults<3>::get_k();
        if ((not R.is_initialized()) or (R.thresh()>thresh)) need=true;
        if (not ncf) need=true;
        if ((not R_square.is_initialized()) or (R_square.thresh()>thresh)) need=true;
        // k must be checked independently of thresh: re-entering a protocol at
        // the same threshold but a different k (a restart, or a user-pinned k)
        // would otherwise reuse R and R_square at the old k and silently mix
        // polynomial orders in every product with the nemos.
        if (R.is_initialized() and R.k()!=k) need=true;
        if (R_square.is_initialized() and R_square.k()!=k) need=true;
        return need;
    };
 
    virtual void invalidate_factors_and_potentials() {
        R.clear();
        R_square.clear();
        ncf.reset();
    };
 
    void construct_nuclear_correlation_factor(const Molecule& molecule,
            const std::shared_ptr<PotentialManager>& pm,
            const std::pair<std::string,double>& ncf_parameter) {
 
        // construct the nuclear correlation factor:
        if (not ncf) {
            ncf=create_nuclear_correlation_factor(world, molecule, pm, ncf_parameter);
        }
 
        // re-project the ncf
        ncf->initialize(FunctionDefaults<3>::get_thresh());
        R = ncf->function();
        R.set_thresh(FunctionDefaults<3>::get_thresh());
        R_square = ncf->square();
        R_square.set_thresh(FunctionDefaults<3>::get_thresh());
    }
 
    /// compute the nuclear gradients
    Tensor<double> compute_gradient(const real_function_3d& rhonemo,
            const Molecule& molecule) const;
 
    /// compute kinetic energy as square of the "analytical" expectation value
 
    /// @param[in]  the nemo orbitals F
    /// @return     T = 1/2 \sum_i \int R^2 U1.U1 F^2 + 2 R^2 U1.grad(F) + R^2 grad(F)^2
    template<typename T, std::size_t NDIM>
    double compute_kinetic_energy(const std::vector<Function<T,NDIM> >& nemo) const {
 
        // T = 0.5\sum_i \int R^2 U1.U1 F^2 - 2 R^2 U1.grad(F) F + R^2 grad(F)^2
        //   = 0.5 (<U1.U1 | rho > + <R^2|grad(F)^2> - 2<R^2 | U1.grad(F) >)
        // note: U1=-grad(R)/R
        //auto id=nemo.front().world().id();
        //auto id1=R_square.world().id();
        //auto worldid=world.id();
        world.gop.fence();
        real_function_3d dens=dot(world,nemo,nemo)*R_square;
        real_function_3d U1dotU1=real_factory_3d(world)
                .functor(NuclearCorrelationFactor::U1_dot_U1_functor(ncf.get()));
        double ke1=inner(dens,U1dotU1);
 
        double ke2=0.0;
        double ke3=0.0;
        //double ke3_real=0.0;
        //double ke3_imag=0.0;
 
        for (size_t axis = 0; axis < NDIM; axis++) {
            real_derivative_3d D = free_space_derivative<double, NDIM>(world, axis);
            const std::vector<Function<T,NDIM> > dnemo = apply(world, D, nemo);
 
            real_function_3d term2=dot(world,dnemo,nemo)*ncf->U1(axis);
            double tmp=-2.0*inner(R_square,term2);
//          ke3_real -=2.0*std::real(tmp);
//          ke3_imag -=2.0*std::imag(tmp);
            ke3 +=tmp;
 
            const real_function_3d term1=dot(world,dnemo,dnemo);
            world.gop.fence();
            ke2 += inner(term1,R_square);
 
        }
//      if (ke3_imag>1.e-8) {
//          print("kinetic energy, imaginary part: ",ke3_imag);
//          MADNESS_EXCEPTION("imaginary kinetic energy",1);
//      }
//      double ke=2.0*(ke1+ke2+ke3_real); // closed shell
        double ke=2.0*(ke1+ke2+ke3); // closed shell
        return 0.5*ke;
    }
 
    /// compute kinetic energy as square of the "analytical" derivative of the orbitals
 
    /// @param[in]  the nemo orbitals F
    /// @return     T = 1/2 \sum_i || grad(R)*F_i + R*grad(F_i)||^2
    template<typename T, std::size_t NDIM>
    double compute_kinetic_energy1(const std::vector<Function<T,NDIM> >& nemo) const {
        timer timer1(world);
        double ke=0.0;
        for (int i=0; i<nemo.size(); ++i) {
            double fnorm2=norm2(world,-1.0*R*ncf->U1vec()*nemo[i] + R*grad(nemo[i]));
            ke+=2.0*fnorm2*fnorm2;
        }
        timer1.end("compute_kinetic_energy1");
        return 0.5*ke;
    }
 
 
    /// compute kinetic energy as square of the "analytical" derivative of the orbitals
 
    /// @param[in]  the nemo orbitals F
    /// @return     T = 1/2 \sum_i || grad(R)*F_i + R*grad(F_i)||^2
    template<typename T, std::size_t NDIM>
    double compute_kinetic_energy1a(const std::vector<Function<T,NDIM> >& nemo) const {
        timer timer1(world);
        double ke=0.0;
        for (int i=0; i<NDIM; ++i) {
            std::vector< std::shared_ptr< Derivative<T,NDIM> > > grad=
                    gradient_operator<T,NDIM>(world);
            double fnorm2=norm2(world,R*(-1.0*ncf->U1(i)*nemo + apply(world,*(grad[i]),nemo)));
            ke+=2.0*fnorm2*fnorm2;
        }
        timer1.end("compute_kinetic_energy1a");
        return 0.5*ke;
    }
 
    /// compute kinetic energy as direct derivative of the orbitals (probably imprecise)
 
    /// @param[in]  the nemo orbitals F
    /// @return     T = 1/2 \sum_i || grad(R*F_i)||^2
    template<typename T, std::size_t NDIM>
    double compute_kinetic_energy2(const std::vector<Function<T,NDIM> >& nemo) const {
 
        // it's ok to use phi here, no regularization necessary for this eigenvalue
        double E_kin = 0.0;
        for (int axis = 0; axis < 3; axis++) {
            real_derivative_3d D = free_space_derivative<double, 3>(world, axis);
            const vecfuncT dphi = apply(world, D,R*nemo);
            E_kin += 0.5 * (inner(world, dphi, dphi)).sum();
            // -1/2 sum <Psi|Nabla^2|Psi> = 1/2 sum <NablaPsi|NablaPsi>   (integration by parts)
        }
        E_kin *= 2.0; // 2 because closed shell
        return E_kin;
    }
 
 
    bool check_convergence(const std::vector<double> energies,
            const std::vector<double> oldenergies, const double bsh_norm,
            const double delta_density, const CalculationParameters& param,
            const double econv, const double dconv) const {
 
        double maxenergychange=fabs(energies.size()-oldenergies.size());    // >0 if oldenergyvec not initialized
        for (auto iter1=energies.begin(), iter2=oldenergies.begin();
                (iter1!=energies.end() and iter2!=oldenergies.end()); iter1++, iter2++) {
            maxenergychange=std::max(maxenergychange,fabs(*iter1 - *iter2));
        }
        double delta_energy=fabs(energies[0]-oldenergies[0]);
 
        bool bsh_conv=param.converge_bsh_residual() ? bsh_norm<dconv : true;
        bool total_energy_conv=param.converge_total_energy() ? delta_energy<econv : true;
        bool each_energy_conv=param.converge_each_energy() ? maxenergychange<econv*3.0 : true;
        bool density_conv=param.converge_density() ? delta_density<dconv : true;
 
        if (world.rank()==0 and param.print_level()>2) {
            std::stringstream line;
            line << "convergence: bshresidual, energy change, max energy change, density change "
                    << std::scientific << std::setprecision(1)
                    << bsh_norm << " " << delta_energy << " "
                    << maxenergychange << " " << delta_density;
            print(line.str());
        }
 
        return (bsh_conv and density_conv and each_energy_conv and total_energy_conv);
    }
 
    World& world;
 
    /// the nuclear correlation factor
    std::shared_ptr<NuclearCorrelationFactor> ncf;
 
    /// the nuclear correlation factor
    real_function_3d R;
 
    /// the square of the nuclear correlation factor
    real_function_3d R_square;
 
 
};
 
 
/// The Nemo class
class Nemo: public NemoBase, public QCPropertyInterface {
    typedef std::shared_ptr<real_convolution_3d> poperatorT;
    friend class PNO;
    friend class TDHF;
 
public:
    /// class holding parameters for a nemo calculation beyond the standard dft parameters from moldft
    struct NemoCalculationParameters : public QCCalculationParametersBase {
        static constexpr char const* tag = "nemo";
 
        NemoCalculationParameters(World& world, const commandlineparser& parser) {
            initialize_nemo_parameters();
            read_input_and_commandline_options(world,parser,tag);
        }
 
        NemoCalculationParameters() {
            initialize_nemo_parameters();
        }
 
        std::string get_tag() const override {
            return std::string("dft");
        }
 
        void initialize_nemo_parameters() {
            // check if parameters are initialized for a nemo calculation already
            if (parameter_exists("ncf")) return;
            initialize<std::pair<std::string,double> > ("ncf",{"slater",2.0},"nuclear correlation factor");
            initialize<bool> ("hessian",false,"compute the hessian matrix");
            initialize<bool> ("read_cphf",false,"read the converged orbital response for nuclear displacements from file");
            initialize<bool> ("restart_cphf",false,"read the guess orbital response for nuclear displacements from file");
            initialize<bool> ("purify_hessian",false,"symmetrize the hessian matrix based on atomic charges");
        }
 
        std::pair<std::string,double> ncf() const {return get<std::pair<std::string,double> >("ncf");}
        bool hessian() const {return get<bool>("hessian");}
 
    };
 
 
public:
    std::filesystem::path work_dir;
 
    /// ctor
 
    /// @param[in]  world1  the world
    /// @param[in]  calc    the SCF
//  Nemo(World& world1, std::shared_ptr<SCF> calc, const std::string inputfile);
 
    Nemo(World& world, const commandlineparser& parser);
 
    /// \p pcm_param defaults to the bare `pcm` group; the solvent still arrives from
    /// param.pcm_data() via PCMParameters::set_derived_values, so a caller that never
    /// parsed a deck keeps working.
    Nemo(World& world, const CalculationParameters& param, const NemoCalculationParameters& nemo_param,
        const Molecule& molecule, const PCMParameters& pcm_param = PCMParameters());
 
    std::string name() const {return "nemo";}
    bool selftest() {return false;}
 
    static void help() {
        print_header2("help page for NEMO");
        print("The nemo code computes Hartree-Fock and DFT energies, gradients and hessians using a nuclear correlation factor");
        print("that regularizes the singular nuclear potential. SCF orbitals for the basis for post-SCF calculations like");
        print("excitation energies (cis), correlation energies (cc2), local potentials (oep), etc\n");
        print("A nemo calculation input is mostly identical to a moldft calculation input, but it uses the additional input");
        print("parameter ncf (nuclear correlation factor)\n");
        print("You can print all available calculation parameters by running\n");
        print("nemo --print_parameters\n");
        print("You can perform a simple calculation by running\n");
        print("nemo --geometry=h2o.xyz\n");
        print("provided you have an xyz file in your directory.\n\n");
        print("To see what a restart archive holds -- geometry, k, the precision it");
        print("converged to, whether it is moldft or nemo orbitals -- without starting");
        print("a calculation:\n");
        print("nemo --restart_info=<prefix>\n");
 
    }
 
    static void print_parameters() {
        NemoCalculationParameters param;
        print("default parameters for the nemo program are");
        param.print("nemo","end");
        print("\n\nthe molecular geometry must be specified in a separate block:");
        Molecule::print_parameters();
    }
 
 
    bool check_converged(const Tensor<double>& x) const {
        double xsq = x.sumsq();
        return (xsq == coords_sum);
    }
 
    virtual double value() {return value(calc->molecule.get_all_coords());}
 
    virtual double value(const Tensor<double>& x);
 
    void load_mos(World& w) {
        calc->load_mos(w);
    }
 
    /// compute dipole moment and gradient at the current geometry
    virtual nlohmann::json analyze() const;
 
    /// compute the nuclear gradients
    Tensor<double> gradient(const Tensor<double>& x);
 
    bool provides_gradient() const {return true;}
 
    /// returns the molecular hessian matrix at structure x
    VibrationalResults hessian(const Tensor<double>& x);
 
    /// construct the fock operator based on the calculation parameters (K or XC?)
    virtual std::shared_ptr<Fock<double,3>> make_fock_operator() const;
 
    /// purify and symmetrize the hessian
 
    /// The hessian should be symmetric, but it is not, because
    /// \f[
    ///  \langle i^{Y_B}|H^{X_A}|i\rangle \neq \langle i|H^{X_A}|i^{Y_B}\rangle
    /// \f]
    /// does holds analytically, but not numerically. If the two numbers
    /// differ, pick the more trustworthy, which is the one with a heavy
    /// atom causing the perturbed density and the light atom being the
    /// nuclear singularity.
    /// @param[in]  hessian the raw hessian
    /// @return     a symmetrized hessian
    Tensor<double> purify_hessian(const Tensor<double>& hessian) const;
 
 
    /// solve the CPHF equations for the nuclear displacements
 
    /// this function computes that part of the orbital response that is
    /// orthogonal to the occupied space. If no NCF's are used this
    /// corresponds to the normal response. If NCF's are used the part
    /// parallel to the occupied space must be added!
    /// \f[
    ///     F^X = F^\perp + F^\parallel
    /// \f]
    /// cf parallel_CPHF()
    /// @param[in]  iatom   the atom A to be moved
    /// @param[in]  iaxis   the coordinate X of iatom to be moved
    /// @return     \ket{i^X} or \ket{F^\perp}
    vecfuncT solve_cphf(const size_t iatom, const int iaxis, const Tensor<double>& fock,
            const vecfuncT& guess, const vecfuncT& rhsconst,
            const Tensor<double>& incomplete_hessian, const vecfuncT& parallel,
            const SCFProtocol& p, const std::string& xc_data) const;
 
    /// solve the CPHF equation for all displacements
 
    /// this function computes the nemo response F^X
    /// \f[
    ///     F^X = F^\perp + F^\parallel
    /// \f]
    /// To reconstruct the unregularized orbital response (not recommended):
    /// \f[
    ///   i^X   = R^X F + R F^X
    /// \f]
    /// The orbital response i^X constructed in this way is automatically
    /// orthogonal to the occupied space because of the parallel term F^\parallel
    /// @return a vector of the nemo response F^X for all displacements
    std::vector<vecfuncT> compute_all_cphf();
 
    /// this function computes that part of the orbital response that is
    /// parallel to the occupied space.
    /// \f[
    ///     F^X = F^\perp + F^\parallel
    /// \f]
    /// If no NCF's are used F^\parallel vanishes.
    /// If NCF's are used this term does not vanish because the derivatives of
    /// the NCF does not vanish, and it is given by
    /// \f[
    ///  F_i^\parallel = -\frac{1}{2}\sum_k|F_k ><F_k | (R^2)^X | F_i>
    /// \f]
    vecfuncT compute_cphf_parallel_term(const size_t iatom, const int iaxis) const;
 
    /// compute the IR intensities in the double harmonic approximation
 
    /// use the projected normal modes; units are km/mol
    /// @param[in]  normalmodes the normal modes
    /// @param[in]  dens_pt the perturbed densities for each nuclear displacement
    Tensor<double> compute_IR_intensities(const Tensor<double>& normalmodes,
            const vecfuncT& dens_pt) const;
 
    std::shared_ptr<SCF> get_calc() const {return calc;}
 
    const NemoCalculationParameters& get_nemo_param() const {return nemo_param;}
    const CalculationParameters& get_calc_param() const {return calc->param;}
 
    PCM get_pcm()const{return pcm;}
 
    /// compute the Fock matrix from scratch
    tensorT compute_fock_matrix(const vecfuncT& nemo, const tensorT& occ) const;
 
    /// return a reference to the molecule
    Molecule& molecule() {return calc->molecule;}
 
    /// return a reference to the molecule
    Molecule& molecule() const {
        return calc->molecule;
    }
 
    /// make the density (alpha or beta)
    real_function_3d make_density(const Tensor<double>& occ,
            const vecfuncT& nemo) const;
 
    /// make the density using different bra and ket vectors
 
    /// e.g. for computing the perturbed density \sum_i \phi_i \phi_i^X
    /// or when using nemos: \sum_i R2nemo_i nemo_i
    real_function_3d make_density(const tensorT & occ,
            const vecfuncT& bra, const vecfuncT& ket, const bool refine=false) const;
 
    /// make the derivative of the density
 
    /// \f$ \nabla\rho = 2R^X R \rho_R + R^2\nabla \rho_R \f$
    /// @param[in]  rhonemo    the regularized density
    /// @param[in]  axis       the component of the nabla operator
    /// @return     the gradient of the *reconstructed* density
    real_function_3d make_ddensity(const real_function_3d& rhonemo,
            const int axis) const;
 
    /// compute the reduced densities sigma (gamma) for GGA functionals
    real_function_3d make_sigma(const real_function_3d& rho1,
            const real_function_3d& rho2) const;
 
 
    /// the Laplacian of the density
 
 
    /// compute the kinetic energy potential using Eq. (16) of
    /// R. A. King and N. C. Handy, “Kinetic energy functionals from the Kohn–Sham potential,”
    /// Phys. Chem. Chem. Phys., vol. 2, no. 22, pp. 5049–5056, 2000.
    real_function_3d kinetic_energy_potential(const vecfuncT& nemo) const;
 
 
    /// smooth a function by projecting it onto k-1 and then average with k
 
    /// kept it here for further testing
    static void smoothen(real_function_3d& f) {
        int k=f.get_impl()->get_k();
        real_function_3d fproj=project(f,k-1);
        real_function_3d freproj=project(fproj,k);
        f=0.5*(f+freproj);
    }
 
protected:
 
    std::shared_ptr<SCF> calc;
 
public:
    const NemoCalculationParameters nemo_param;
 
protected:
    projector_irrep symmetry_projector;
 
public:
 
    /// return the symmetry_projector
    projector_irrep get_symmetry_projector() const {
        return symmetry_projector;
    }
 
private:
 
    /// sum of square of coords at last solved geometry
    mutable double coords_sum;
 
protected:
    /// a poisson solver
    std::shared_ptr<real_convolution_3d> poisson;
 
    /// asymptotic correction for DFT
    AC<3> ac;
 
//    /// apply the AC scheme of Tozer/Handy with the multipole approximation
//    Function<double,3> apply_ac(const Function<double,3>& vxc)const{
//      return ac.apply(vxc);
//    }
//
//    /// apply the AC scheme of Tozer/Handy using the hartree potential
//    Function<double,3> apply_ac(const Function<double,3>& vxc, const Function<double,3>& vhartree)const{
//      return ac.apply(vxc,vhartree);
//    }
//
//    /// apply the AC scheme of Tozer/Handy
//    Function<double,3> apply_ac_excited(Function<double,3>& vxc, const Function<double,3>& vhartree)const{
//      return ac.apply_potential(vxc,vhartree);
//    }
 
private:
    /// polarizable continuum model
    PCM pcm;
//  AC<3> ac;
 
protected:
    /// adapt the thresholds consistently to a common value
    void set_protocol(const double thresh) {
 
        // sets FunctionDefaults, including k -- which SCF::set_protocol derives
        // from thresh unless the user pinned it
        calc->set_protocol<3>(world,thresh);
 
        if (need_recompute_factors_and_potentials(thresh)) {
            timer timer1(world,get_calc_param().print_level()>2);
            get_calc()->make_nuclear_potential(world);
            construct_nuclear_correlation_factor(calc->molecule, calc->potentialmanager, get_nemo_param().ncf());
            timer1.end("reproject ncf");
        }
 
        // (re) construct the Poisson solver
        poisson = std::shared_ptr<real_convolution_3d>(
                CoulombOperatorPtr(world, get_calc_param().lo(), FunctionDefaults<3>::get_thresh()));
 
        // Bring the MOs to the new k and thresh. This must come AFTER the ncf
        // has been rebuilt, because the normalization inside reproject_mos uses
        // R as the metric and would otherwise mix polynomial orders itself.
        reproject_mos(calc->amo,R);
        reproject_mos(calc->bmo,R);
 
        // The AO basis has to follow k as well. moldft reprojects it inside its
        // protocol loop (SCF.h, MolecularEnergy::value); nemo projected it once
        // outside the ladder, so a k change left it behind -- and Nemo::localize
        // hands it to the Localizer next to the freshly reprojected nemos.
        const int k=FunctionDefaults<3>::get_k();
        if (calc->ao.size()>0 and calc->ao.front().k()!=k) {
            if (world.rank()==0 and get_calc_param().print_level()>2)
                print("reprojecting the AO basis from k =",calc->ao.front().k(),"to k =",k);
            calc->ao.clear();
            world.gop.fence();
            calc->ao=calc->project_ao_basis(world,calc->aobasis);
        }
 
    }
 
    /// solve the HF equations
    double solve(const SCFProtocol& proto);
 
    /// given nemos, compute the HF energy using the regularized expressions for T and V
    std::vector<double> compute_energy_regularized(const vecfuncT& nemo, const vecfuncT& Jnemo,
            const vecfuncT& Knemo, const vecfuncT& Unemo) const;
 
    /// compute the reconstructed orbitals, and all potentials applied on nemo
 
    /// to use these potentials in the fock matrix computation they must
    /// be multiplied by the nuclear correlation factor
    /// @param[in]  nemo    the nemo orbitals
    /// @param[out] Jnemo   Coulomb operator applied on the nemos
    /// @param[out] Knemo   exchange operator applied on the nemos
    /// @param[out] pcmnemo PCM (solvent) potential applied on the nemos
    /// @param[out] Unemo   regularized nuclear potential applied on the nemos
    /// @param[out] xcflux  the vector field Y_i that the orbital update pushes
    ///                     through the Green's function, see
    ///                     XCOperator::weak_xc_terms. Assigned in the weak form
    ///                     only and left EMPTY otherwise, which is how the caller
    ///                     tells the two forms apart.
    /// @param[out] fock_xc the xc block of the Fock matrix. In the weak form it
    ///                     cannot be recovered from xcnemo any more, because what
    ///                     is missing from xcnemo is exactly the term that has no
    ///                     multiplicative representation. Assigned in the weak
    ///                     form only and left untouched otherwise.
    void compute_nemo_potentials(const vecfuncT& nemo,
            vecfuncT& Jnemo, vecfuncT& Knemo, vecfuncT& xcnemo, vecfuncT& pcmnemo,
            vecfuncT& Unemo, std::vector<vecfuncT>& xcflux, tensorT& fock_xc) const {
        compute_nemo_potentials_impl(nemo, Jnemo, Knemo, xcnemo, pcmnemo, Unemo,
                xcflux, fock_xc, true);
    }
 
    /// compute all potentials applied on nemo, without the weak-form split
 
    /// The pre-weak-form signature, kept for callers that have no use for the
    /// flux. It never opts in to the weak form, whatever `xc_weak_gga` says, so
    /// xcnemo always carries the complete multiplicative xc potential and the
    /// xc block of the Fock matrix can be read off it as before. Silently
    /// discarding xcflux instead would drop the semilocal term.
    void compute_nemo_potentials(const vecfuncT& nemo,
            vecfuncT& Jnemo, vecfuncT& Knemo, vecfuncT& xcnemo, vecfuncT& pcmnemo,
            vecfuncT& Unemo) const {
        std::vector<vecfuncT> xcflux;
        tensorT fock_xc;
        compute_nemo_potentials_impl(nemo, Jnemo, Knemo, xcnemo, pcmnemo, Unemo,
                xcflux, fock_xc, false);
    }
 
    /// implementation of both compute_nemo_potentials forms
 
    /// @param[in]  allow_weak  opt in to the weak form; it is then used iff
    ///                         the `xc_weak_gga` parameter asks for it
    void compute_nemo_potentials_impl(const vecfuncT& nemo,
            vecfuncT& Jnemo, vecfuncT& Knemo, vecfuncT& xcnemo, vecfuncT& pcmnemo,
            vecfuncT& Unemo, std::vector<vecfuncT>& xcflux, tensorT& fock_xc,
            const bool allow_weak) const;
 
    /// return the Coulomb potential
    real_function_3d get_coulomb_potential(const vecfuncT& psi) const;
 
    /// compute the incomplete hessian
 
    /// incomplete hessian is the nuclear-nuclear contribution, and the
    /// contribution from the second derivative of the nuclear potential,
    /// and also the derivative of the nuclear correlation factor.
    /// i.e. all contributions that *do not* contain the regularized perturbed
    /// density, but it will contain parts of the perturbed density
    Tensor<double> make_incomplete_hessian() const;
 
    /// compute the complementary incomplete hessian
 
    /// @param[in]  xi the response functions including the parallel part
    Tensor<double> make_incomplete_hessian_response_part(
            const std::vector<vecfuncT>& xi) const;
 
    /// compute the constant term for the CPHF equations
 
    /// mainly all terms with the nuclear correlation factor's derivatives
    vecfuncT make_cphf_constant_term(const size_t iatom, const int iaxis,
            const vecfuncT& R2nemo, const real_function_3d& rhonemo) const;
 
public:
 
    bool is_dft() const {return calc->xc.is_dft();}
 
    bool do_pcm() const {return get_calc_param().pcm_data() != "none";}
    
    /// the asymptotic correction is defunct: its `ac_data` parameter was removed,
    /// and the code paths guarded by do_ac() are kept but never taken. It was
    /// never reconciled with the weak xc form, whose Fock block is built from the
    /// uncorrected potential.
    bool do_ac() const {return false;}
 
    AC<3> get_ac() const {return ac;}
 
    bool do_symmetry() const {return (symmetry_projector.get_pointgroup()!="C1");}
 
protected:
 
    /// localize the nemo orbitals
    vecfuncT localize(const vecfuncT& nemo, const double dconv, const bool randomize) const;
protected:
    /// return the threshold for vanishing elements in orbital rotations
    double trantol() const {
        return calc->vtol / std::min(30.0, double(get_calc()->amo.size()));
    }
 
    void make_plots(const real_function_3d &f,const std::string &name="function")const{
        double width = FunctionDefaults<3>::get_cell_min_width()/2.0 - 1.e-3;
        plot_plane(world,f,name);
        coord_3d start(0.0); start[0]=-width;
        coord_3d end(0.0); end[0]=width;
        plot_line(("line_"+name).c_str(),1000,start,end,f);
    }
 
    /// save a function
    template<typename T, size_t NDIM>
    void save_function(const std::vector<Function<T,NDIM> >& f, const std::string name) const;
 
    /// load a function
    template<typename T, size_t NDIM>
    void load_function(std::vector<Function<T,NDIM> >& f, const std::string name) const;
 
};
 
/// save a function
template<typename T, size_t NDIM>
void Nemo::save_function(const std::vector<Function<T,NDIM> >& f, const std::string name) const {
    if (world.rank()==0) print("saving vector of functions",name);
    archive::ParallelOutputArchive<archive::BinaryFstreamOutputArchive> ar(world, name.c_str(), 1);
    ar & f.size();
    for (const Function<T,NDIM>& ff:f)  ar & ff;
}
 
/// load a function
template<typename T, size_t NDIM>
void Nemo::load_function(std::vector<Function<T,NDIM> >& f, const std::string name) const {
    if (world.rank()==0) print("loading vector of functions",name);
    archive::ParallelInputArchive<archive::BinaryFstreamInputArchive> ar(world, name.c_str(), 1);
    std::size_t fsize=0;
    ar & fsize;
    f.resize(fsize);
    for (std::size_t i=0; i<fsize; ++i) ar & f[i];
}
 
}
 
#endif /* NEMO_H_ */