First-principles study on sum-frequency generation spectroscopy of methanol adsorbed on TiO2(110) surface: Effects of substrate and molecular coverages

Zhitao Shen; Chih-Kai Lin; Chaoyuan Zhu; Sheng Hsien Lin

doi:10.1063/1.5088885

First-principles study on sum-frequency generation spectroscopy of methanol adsorbed on TiO₂(110) surface: Effects of substrate and molecular coverages

J Chem Phys. 2019 May 14;150(18):184112. doi: 10.1063/1.5088885.

Authors

Zhitao Shen¹, Chih-Kai Lin², Chaoyuan Zhu¹, Sheng Hsien Lin¹

Affiliations

¹ Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan.
² Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan.

PMID: 31091896
DOI: 10.1063/1.5088885

Abstract

In this work, starting from the general theory of sum-frequency generation (SFG), we proposed a computational strategy utilizing density functional theory with periodic boundary conditions to simulate the vibrational SFG of molecules/solid surface adsorption system. The method has been applied to the CH₃OH/TiO₂(110) system successfully. Compared with the isolated molecule model, our theoretical calculations showed that the TiO₂ substrate can significantly alter the second-order susceptibilities of a methanol molecule which is directly related to the SFG intensity. In addition, the SFG spectra have obvious changes while the methanol coverage increases, especially for the OH vibration peaks. Our theoretical spectra agree reasonably well with experimental measurements at 1 ML coverage, and an interesting peak which is absent in the theoretical spectra is tentatively assigned to some CH₃ stretch vibration of methanol adsorbed on the oxygen vacancy of TiO₂.