Inclusion of the most important multi-particle interactions in the AMBER force field and optimization of energy parameters of the revised force field

A new functional form for force field of non-covalent interactions is developed. Besides traditional members, it involves induced (by partial charges) polarization of all atoms as well as three-particle dispersion interactions of atoms with covalent bonds. The corresponding new members are added to a standard AMBER force field. Within this unified functional form of the force field, parameters of all types of non-covalent interactions are optimized using data on molecular crystals. A noticeable increase in correlation coefficient between calculated and experimental energy of cohesion of molecules in molecular crystals is shown.