The electrostatic properties of water molecules in condensed phases: an<i>ab initio</i>study

Ab initio calculations are reported for water molecules in several condensed phases, looking particularly at the electrostatic properties of individual molecules. The approach is based on the flux of the electron density gradient to identify the electron distribution of individual molecules. Molecular dipole and quadrupole moments are calculated for molecules in a variety of environments, using configurations generated from classical and ab initio molecular dynamics simulations at 300 K. These make it possible to characterize differences between classical models and ab initio calculations with both fixed and varying molecular geometry. Our main result is an estimate of the average dipole and quadrupole moments for the water molecule in liquid and solid phases.