Theoretical and Solid-State NMR Study of Acetylene Adsorption on Nano-Sized MgO

Abstract

We present a combined density functional theory, gauge-including atomic orbital (GIAO), in situ 13C MAS NMR, and in situ infrared study of acetylene adsorption on nano-sized MgO powder. Geometries were optimized using the hybrid B3LYP exchange-correlation functional and triple-ζ basis sets. By utilizing models of the surface ranging in size from Mg4O4 to Mg8O8, we optimized geometries for a variety of surface-bound species on corner and edges sites. No stable dissociation products on the flat, (100)-like surface of an Mg12O12 cluster could be obtained theoretically, in agreement with a previous ultrahigh vacuum surface science experiment. We also present GIAO-restricted Hartree−Fock predictions of the 13C chemical shifts of all species and their vibrational frequencies. The agreement between theory and experiment is outstanding. Both the theoretical and experimental results strongly support the formation of an acetylide on the MgO surface, while an alternative vinylidene species is not present. A minority...