Inclusion of charge and polarizability fluxes provides needed physical accuracy in molecular mechanics force fields

Abstract Physical accuracy in MM calculations requires maximally correct forces in addition to structures and energies. This requires inclusion of charge and polarizability fluxes in the energy function. Using our spectroscopically determined force field, which is designed to include these, we present three examples of the improved physical predictions that result from the incorporation of charge fluxes: the reproduction of the water angle opening on going from the isolated molecule to the liquid, the reproduction of the ψ peptide torsion potential with only a single threefold (almost zero barrier) Fourier term, and reproduction of the quantum-mechanical MD ϕ , ψ map of a dipeptide analog.