Intermolecular dynamical charge fluctuations in water: a signature of the H-bond network

We report a simulation of deuterated water using a Car-Parrinello approach based on maximally localized Wannier functions. This provides local information on the dynamics of the hydrogen-bond network and on the origin of the low-frequency infrared activity. The oscillator strength of the translational modes, peaked around 3c200\u2009\u2009cm-1, is anisotropic and originates from intermolecular\u2014not intramolecular\u2014charge fluctuations. These fluctuations are a signature of a tetrahedral hydrogen-bonding environment