A new approach to pairwise potentials for water-water interactions

The implementation of a theoretical model of a water-water hydrogen bond, which acts with two distinctly differing forces, is made here with the modification of the classical Lennard-Jones potential implemented in 768 molecule ice Ih cell molecular dynamics simulations. Varying forces result from the modified pairwise Lennard-Jones potential in response to the relative orientation of the water dimer it is acting between. Hence, the relatively fixed orientations of the water pairs occurring in ice Ih are taken into account, and the new potential is able to reproduce different energies of hydrogen bond stretching modes - most notably, being able to reproduce two hydrogen bond stretching modes between different water pairs in the simulated system, as observed in inelastic neutron scattering experiments on ices.