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48. Hydrogen bond dynamics in heavy water studied with quantum dynamical simulations.

      F. Paesani, Phys. Chem. Chem. Phys. 13, 19865 (2011). [link]

The structure and dynamics of the hydrogen-bond network in heavy water (D2O) is studied as a function of the

temperature using quantum dynamical simulations. Our approach combines an ab initio-based representation

of the water interactions with an explicit quantum treatment of the molecular motion. A direct connection between

the calculated linear and nonlinear vibrational spectra and the underlying molecular dynamics is made, which

provides new insights into the rearrangement of the hydrogen-bond network in heavy water. A comparison with

previous calculations on liquid H2O suggests that tunneling does not effectively contribute to the dynamics of the

water hydrogen-bond network above the melting point. However, the effects of nuclear quantization are not

negligible at all temperatures and become increasingly important near the melting point, which is in agreement

with recent experimental analysis of the structural properties of liquid water as well as of the proton momentum

distribution in supercooled water.

47. Temperature-dependent infrared spectroscopy of water from a first-principles approach.

      F. Paesani, J. Phys.Chem. A 115, 6861 (2011). [link]

The structure and dynamics of the hydrogen-bond network in water is investigated as a function of the

temperature through the application of a first-principles approach that combines an ab-initio-based water

potential with an explicit quantum treatment of the molecular motion. A molecular-level picture of the

rearrangement of the hydrogen-bond network is derived from the direct analysis of linear and nonlinear

vibrational spectra. The results indicate that good agreement with the available experimental data is obtained

when the temperature scale is defined relative to the corresponding melting points. In particular, the

theoretically predicted energy barriers and time scales associated with the hydrogen-bond dynamics are

closely comparable to the experimental values obtained from two-dimensional and pump-probe infrared

spectra. The present analysis will also serve as a guide for future developments of an improved ab initio-based

model capable to reproduce the properties of water in different environments and under different conditions.