Neutral Tantalum−Carbide Clusters:  A Multiphoton Ionization and Density Functional Theory Study

Abstract

Neutral tantalum−carbide clusters, Ta m C n (m = 1−6, n = 1−7), have been formed in a supersonic expansion following the reaction of tantalum and acetylene in a laser ablation source. These clusters have been subjected to multiphoton ionization at 532 and 355 nm and the mass spectra recorded in a reflectron time-of-flight mass spectrometer. The cluster distributions show a drop 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 distorted cube of stoichiometry Ta4C4. The structure of Ta4C4 is shown to be a distorted 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 there is competition for the carbon atoms to bond to either the face or the edge of the tantalum triangle.

Threshold photoionization and density functional theory studies of bimetallic-carbide nanocrystals and fragments: Ta3ZrCy (y=–4)

“…Our group has previously conducted an experimental and computational examination of the Ta 4 C y ͑y =0-4͒ clusters, 14,15 the results of which supported the 2 ϫ 2 ϫ 2 nanocrystal structure of Ta 4 C 4 determined via IR-REMPI spectroscopy. 4 In this paper we report the generation of bimetallic tantalum-zirconium-carbide clusters of the form Ta x ZrC y using a double ablation cluster source.…”

Spectroscopic observation of gold-dicarbide: Photodetachment and velocity map imaging of the AuC2 anion

“…Gold-carbide clusters were produced within a Smalley-type laser ablation source modelled on our existing designs. 24 The source was operated with benzene seeded in helium gas to produce the metal-carbon products. The clusters exit the source and expand towards a two stage WileyMcLaren type time of flight where anion species are pulse extracted orthogonally into a drift region.…”

Electronic structure of cubic HfxTa1–xCy carbides from X-ray spectroscopy studies and cluster self-consistent calculations

“…The crystal structure of HfC x belongs also to the NaCl-type with the homogeneity range corresponding to 0.56 ≤ x ≤ 1.00 [10]. Tantalum and hafnium carbides reveal some interesting properties in nano-size states: tantalum and hafnium are capable of forming cluster ions Ta m C n + (m = 1-11, n = 1-26) and Hf 8 C 12 + [11][12][13], while neutral clusters Ta m C n (m = 1-6, n = 1-7) were obtained by Heaven et al [14] in a supe-0925-8388/$ -see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2007.08.018 rionic expansion following the reaction of tantalum in a laser absorption source.…”

“…doi:10.1016/j.jallcom.2007.08.018 rionic expansion following the reaction of tantalum in a laser absorption source. Density functional theory calculations [14] reveal that the smaller Ta m C n clusters tend to form fragments of face-centred cubes, leading to the formation of a distorted Ta 4 C 4 cube. Additionally, as it has been established by Fukunada et al [15], in TaC x nanorods and nanoparticles, the superconducting properties correlate with the lattice parameter.…”