The structure of water at interfaces through ab initio simulations of non-linear spectroscopy*

Hydrogen evolution through heterogeneous catalysis is an increasingly widespread method of storing energy generated from renewable sources, and as such is becoming a central part of green energy grids. Understanding the structure of water at solid surfaces is vital to find more efficient and cost-effective catalysts of this reaction, and sum-frequency generation spectroscopy provides a surface-specific method of investigating these structures.[1] We present a new framework for ab initio calculations of the sum-frequency response of water-solid interfaces, avoiding the need for an arbitrary molecular decomposition of the polarizability and dipole moment of the system by evaluating these quantities using real space integrals.[2] This allows us to investigate the effect of this decomposition on the sum-frequency response of the much-studied water/vacuum interface. This approach also enables us to account explicitly for the contribution of the solid to the polarizability and dipole moment of the interface, which are commonly neglected. We demonstrate the impact of these contributions on the sum-frequency response of water/metal oxide interfaces.

[1] A. Morita, J. Hynes, J. Phys. Chem. B 106, 673 (2002)

[2] H. Shang et al, New J. Phys. 20, 073040 (2018)