ABSTRACT
The paper explores the interplay between the local environment in liquid water and two key properties of the water molecule, namely its average electronic distribution and the quantum rotational uncertainty of the molecule. A mean-field approach is presented describing the electrostatic environment experienced by water molecule in liquid state, which is used to extract the corresponding hyper- and highorder polarizabilities. It is then shown that the average total dipole moment for the water molecule in the liquid state can be linked to experimental refractive index data by means of a formal framework that relates the temperature dependence of the effective molecular polarizability to the average local electric field experienced by a liquid water molecule over a chosen temperature range. The local environment in liquid water is found to rise to substantially elevated dipole moments, with an almost 10% variation in the dipole being observed over the temperature range 273 to 373 K. The extension of the centroid molecular dynamics (CMD) method to rotational motion of a molecule is also discussed. An algorithm is presented that homogeneously samples the orientational neighborhood associated with the quantum degrees of freedom of a specified orientational centroid; as a critical component of this development a general definition for an orientational centroid (or average rotation) is presented. The application of this methodology in quantum simulations of liquid water is discussed. It is shown that while quantization significantly impacts the bulk properties of water, it is also demonstrated that the local environment in liquid water can influence the quantum dispersion of the molecule in unexpected ways.
