An Empirical Three-Body Potential for Tetrahedral Liquids

A simple three-body empirical potential function is proposed for computational studies of liquid water and other liquids possessing tetrahedral coordination. The potential is derived from a linear combination of nearly degenerate structural forms. The potential presented has three types of minima associated with the structure of liquid water; one nearest neighbor and two next-nearest-neighbor minima. The inner minima corresponds to the hydrogen bonded distance of 2.78{\AA} present in liquid water whilst the other two minima represent the non-hydrogen bonded neighbor normally present at a tetrahedral distance of 4.5{\AA} but which begins to occupy an interstitial distance of 3.4{\AA} with increased pressure, increased temperature, increased confinement, and changes in pH. The 3.4{\AA} distance is populated at the expense of the 4.5{\AA} distance and it is these two explicit bonding distances in the liquid which gives rise to the anomalous behavior of liquid water.