Spatial correlation of dipole fluctuations in liquid water

Abstract

The molecular dipole moments and local environments of water in its liquid phase were examined for a series of first-principles Gibbs ensemble Monte Carlo simulations along the vapour–liquid coexistence curve using the Becke–Lee–Yang–Parr (BLYP) and Perdew–Burke–Ernzerhof (PBE) exchange/correlation density functionals. Molecular dipole moments were computed using maximally localized Wannier functions with the Berry phase scheme, while the structure was analysed with respect to tetrahedral order parameter and hydrogen bonding. Increasing the temperature results in a decrease of both the average molecular dipole moment and the local structure, although the width of the dipole distribution remains fairly constant. A correlation is found between the extent of the local structure and the magnitude of the molecular dipole moment, but this correlation is limited to the first solvation shell.

Acknowledgements

We thank Larry Fried and Charlie Westbrook for their ongoing support of this work. We also thank Juerg Hutter, Joost VandeVondele and Matthias Krack for many stimulating discussions. Financial support from the National Science Foundation (CTS-0553911), a 3M Foundation Graduate Fellowship (MJM), and a Department of Energy Computational Science Graduate Fellowship (MJM) are gratefully acknowledged. Part of this work was performed under the auspices of the US Department of Energy by the University of California Lawrence Livermore National Laboratory (LLNL) under contract No. W-7405-Eng-48. Computer resources were provided by Livermore Computing and the Minnesota Supercomputing Institute.