Water in contact with a solid surface may have properties substantially different from bulk ones, depending on the surface hydrophobicity/hydrophilicity, as well as on the surface charge. In this talk I will present a combined simulation and experimental approach aiming to understand structural and dynamical properties of water at the interface with calcium/fluorite over a wide range of pH conditions. Density functional theory (DFT) -based molecular dynamics simulations are used to compute phase-resolved Sum Frequency Generation (SFG) spectra and to provide a molecular interpretation of the experimental spectra and a microscopic description of the interfaces. In a second part of the talk, I will also present our approach to understand vibrational energy relaxation at interfaces using non-equilibrium molecular dynamics simulations and suitable descriptors based on projected vibrational density of states. The data from the simulations permit to interpret the experimental pump-probe SFG spectra. We find that the energy relaxation, mostly mediated by an OH-OH stretching coupling, is highly heterogeneous and strongly depends on the environment, where a strong hydrogen bond network can transport energy with a timescale of 200 fs, whereas a weaker network can slow down the transport of a factor 2-3. Differences between interfacial and bulk water relaxation will be discussed.

Water at fluorite/water interface: Structure and vibrational spectroscopy from <i>ab initio </i>simulations

2019 Fall National Meeting

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Water at fluorite/water interface: Structure and vibrational spectroscopy from ab initio simulations