Orientational pair correlation function of liquid water from a reverse Monte Carlo study

A reverse Monte Carlo simulation of liquid water at room temperature is made by fitting the partial pair correlation functions of our model system to those obtained from neutron scattering experiments. The atoms in a molecule are held together by non-rigid bonds under geometric constraints. In order to study the structure of the converged configurations, a spherical harmonic expansion of the orientational pair correlation function is made and the first few coefficients are compared to those extracted from neutron scattering data. Two possible intramolecular sets of constraints are discussed. One is entirely based on the experimental partial pair correlation functions and the other is an almost-rigid bonds model using the intramolecular vibrational force constants taken from a molecular dynamics simulation.