Calculations/Dipolar-Gas-Simulator/+VariationalSolver2D/@Calculator/calculateVariationalEnergy.m

function E = calculateVariationalEnergy(this, psi, Params, ell, Transf, V)
                               
    g_eff       = Params.gs      * (1/(sqrt(2*pi)*ell));
    gamma_eff   = Params.gammaQF * (sqrt(2/5)/(pi^(3/4)*ell^(3/2)));
    Ez          = (0.25/ell^2) + (0.25*Params.gz*ell^2);
    
    % Parameters
    KEop        = 0.5*(Transf.KX.^2+Transf.KY.^2);
    normfac     = Params.Lx*Params.Ly/numel(psi);

    % DDIs
    VDk         = this.calculateVDkWithCutoff(Transf, Params, ell); % VDk depends on the variational parameters. THIS HAS TO BE RECALCULATED HERE FOR THE CONSTRAINED OPTIMIZATION TO WORK!
    frho        = fftn(abs(psi).^2);
    Phi         = real(ifftn(frho.*VDk));
    Eddi        = 0.5*Params.gdd*Phi.*abs(psi).^2/(sqrt(2*pi)*ell);
    Eddi        = sum(Eddi(:))*Transf.dx*Transf.dy;
    
    % Kinetic energy
    Ekin        = KEop.*abs(fftn(psi)*normfac).^2;
    Ekin        = sum(Ekin(:))*Transf.dkx*Transf.dky/(2*pi)^2;
    
    % Potential energy
    Epot        = V.*abs(psi).^2;
    Epot        = sum(Epot(:))*Transf.dx*Transf.dy;

    % Contact interactions
    Eint        = 0.5*g_eff*abs(psi).^4;
    Eint        = sum(Eint(:))*Transf.dx*Transf.dy;
    
    % Quantum fluctuations
    Eqf         = 0.4*gamma_eff*abs(psi).^5;
    Eqf         = sum(Eqf(:))*Transf.dx*Transf.dy;
    
    % Total
    E           = Ez*Params.N + Ekin + Epot + Eint + Eddi + Eqf;
    
end