Structural and Electronic Properties of Different Terminations for Quartz (001) Surfaces as Well as Water Molecule Adsorption on It: A First-Principles Study

摘要

Structural and electronic properties of Si termination, O-middle termination, and O-rich terminations of a quartz (001) surface as well as water molecule adsorption on it were simulated by means of density functional theory (DFT). Calculated results show that the O-middle termination exposing a single oxygen atom on the surface is the most stable model of quartz (001) surface, with the lowest surface energy at 1.969 J·m ?2 , followed by the O-rich termination and Si termination at 2.892 J·m ?2 and 2.896 J·m ?2 , respectively. The surface properties of different terminations mainly depend on the surface-exposed silicon and oxygen atoms, as almost all the contributions to the Fermi level (E F ) in density of states (DOS) are offered by the surface-exposed atoms, especially the O2p state. In the molecular adsorption model, H 2 O prefers to adsorb on the surface Si and O atoms, mainly via O 1 –H 1 bond at 1.259 ? and Si 1 –O w at 1.970 ? by Van der Waals force and weak hydrogen bond with an adsorption energy of ?57.89 kJ·mol ?1 . In the dissociative adsorption model, the O-middle termination is hydroxylated after adsorption, generating two new Si–OH silanol groups on the surface and forming the O w H 2 ···O 4 hydrogen bond at a length of 2.690 ?, along with a large adsorption energy of ?99.37 kJ·mol ?1 . These variations in the presence of H 2 O may have a great influence on the subsequent interfacial reactions on the quartz surface.