Mw. Heaven et al., Neutral tantalum-carbide clusters: A multiphoton ionization and density functional theory study, J PHYS CH A, 104(15), 2000, pp. 3308-3316
Neutral tantalum-carbide clusters, TamCn (m = 1-6, n = 1-7), have been form
ed in a supersonic expansion following the reaction of tantalum and acetyle
ne in a laser ablation source. These clusters have been subjected to multip
hoton ionization at 532 and 355 nm and the mass spectra recorded in a refle
ction lime-of-night mass spectrometer. The cluster distributions show a dro
p off after m = 4 suggesting the stabilization of clusters containing four
tantalum atoms. We have investigated the structures of these clusters using
density functional theory and shown that the smaller clusters tend to Form
fragments of face-centered cubes, culminating in the formation of a distor
ted cube of stoichiometry Ta4C4. The structure of Tr4C4 is shown to be a di
storted tetrahedron, or "butterfly", made up of four tantalum atoms with a
carbon atom bonded to each face. The theoretical calculations also indicate
that clusters containing three tantalum atoms form a triangle and that the
re is competition for the carbon atoms to bond to either the face or the ed
ge of the tantalum triangle.