title: Anion photoelectron spectroscopy and density functional investigation of vanadium carbide clusters.
abstract: The influence of source conditions on vanadium-carbon cluster formation in a methane-vanadium plasma is explored and analyzed by photoelectron spectroscopy, revealing that the metal-carbon ratio has substantial influence over the cluster products. Experiments that employ large methane content produce carbon-rich mono- and divanadium carbides. The carbon-rich clusters show a preference for the formation of cyclic neutral and linear ionic structures. When the methane concentration is decreased, VmCn clusters are formed with m = 1-4 and n = 2-8. The photoelectron spectra of clusters formed under these conditions are indicative of a three-dimensional network. We have measured a significantly lower vertical electron affinity for the VC2, V2C3, and V4C6 clusters compared with proximate species. Interestingly, the VC2 species is a proposed building block of the M8C12 Met-Car cluster, and the 2,3 and 4,6 clusters correspond to the 1/4 and 1/2 Met-Car cages, respectively. This correlation is taken as evidence of their importance in the formation of the larger Met-Car species. These results are supported by density functional theory (DFT) calculations carried out at the PBE/GGA level.
authors.affiliation: Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: K L
authors.initials: KL
authors.lastname: Knappenberger
authors.forename: C E
authors.initials: CE
authors.lastname: Jones
authors.forename: M A
authors.initials: MA
authors.lastname: Sobhy
authors.forename: I
authors.initials: I
authors.lastname: Iordanov
authors.forename: J
authors.initials: J
authors.lastname: Sofo
authors.forename: A W
authors.initials: AW
authors.lastname: Castleman