Theoretical Study of Doubly Resonant Sum-Frequency Vibrational Spectroscopy for 1,1′-Bi-2-naphthol Molecules on Water Surface

Abstract

By combining molecular dynamics (MD) simulation and density functional theory (DFT) calculations, we investigate the surface doubly resonant sum-frequency vibrational spectroscopy (SFVS) for a monolayer of R-1,1′-bi-2-naphthol (R-BN) molecules on water surface. MD simulations indicate that the R-BN molecules stand perpendicularly on the water surface due to hydrogen bonding with the water molecules. DFT and time-dependent density functional theory (TDDFT) methods are employed to obtain potential energy shifts, transition dipoles, and their derivatives, which are then used to calculate both the Franck–Condon and Herzberg–Teller terms to the surface hyperpolarizabilities. The theoretical SFVS agrees well with the experimental result. The origin of the SFVS peaks and symmetry properties of the hyperpolarizabilities tensor are also analyzed, which indicates that theoretical computations can obtain the most important components that are helpful for experimental SFVS analysis. The current work shows that theoretical calculations can provide useful detailed molecular information, such as molecular structure, orientation, and excited structure at interfaces, in studies of surface doubly resonant SFVS.