Lateral interaction and spectroscopic constants of CO adsorbed on ZnO

The adsorption of carbon monoxide on a six-layer supercell ZnO( 10 1 ¯ 0 ) was studied using DFT with periodic methodology, PW91 as functional and plane waves as basis set. Furthermore, vibrational energies and spectroscopic constants for the Zn–C interaction were determined. The geometric parameters of adsorbed CO are in accordance with available experimental and theoretical data. Carbon monoxide adsorption sites as a function of coverage were also studied, showing CO vibrational frequency decrease with coverage increases in agreement with experimental results. The adsorption energy shows a decrease with coverage, from 60.9 to 50.8 kJ mol −1 , which is supported by experimental data. Structural analyses indicated that the change found in the adsorption energy and the associated frequency shift is explained by the surface relaxation upon adsorption. We have reported the calculated spectroscopic constants for CO adsorption, for the first time in the literature. Vibrational frequency found from potential energy curve has the same behavior of adsorption energies. Density of states analysis of CO adsorption also showed agreement with experimental results. A decrease of 4σ–5σ gap was obtained, resulting from the stabilization of both peaks in agreement with experimental results.