Gas phase ion mobility measurements have been used to examine the geometries of silicon-doped carbon cluster cations, CnSi+ (n = 3−69). The observed isomers resemble those found for pure carbon clusters:  linear chains, monocyclic, bicyclic, and polycyclic rings, graphite sheets, and fullerenes. Generally, the silicon atom substitutes for a carbon atom and has only a minor effect on the structure. The linear chain and monocyclic ring isomers coexist for CnSi+ clusters over a wider range than for pure carbon cluster cations. The results provide the first conclusive experimental evidence that C2n-1Si+ fullerenes with an even number of atoms are closed-cage structures with the silicon atom networked into the cage. For C2nSi+ fullerenes with an odd number of atoms the silicon atom appears to be exohedral.

Structures of Silicon-Doped Carbon Clusters

Density functional calculations with simulated annealing have been performed for singly charged mixed silicon‐carbon cluster anions SinCm− and for neutral SinCm clusters with up to eight atoms. The calculations predict the existence of a number of previously unknown isomers and identify two classes of anion structure: carbon‐rich (chainlike) and silicon‐rich (three‐dimensional), with pronounced differences in the vertical detachment energies (VDE, transitions to states of the neutral clusters). The results provide insight into recent photoelectron detachment measurements on the anions.

Structure and bonding in mixed silicon–carbon clusters and their anions

Fourier transform infrared matrix measurements carried out in conjunction with ab initio calculations reported in a companion paper by Rittby have resulted in the first identification of two fundamental vibrations, the C=C stretching mode ν3(σu)=1955.2 cm−1, and the Si–C stretching mode ν4(σu)=898.9 cm−1, of the SiC3Si cluster formed by trapping the products of the vaporization of silicon/carbon mixtures in Ar at 10 K. The observed frequencies, relative intensities, and 13C, 29Si, and 30Si isotopic shifts for the ν3 and ν4 vibrations are in good agreement with the results of the ab initio calculations at the second‐order many‐body perturbation theory [MBPT(2)] level which predict a linear centrosymmetric geometry for the ground state of SiC3Si. The results of force constant adjustment calculations are consistent with the proposed vibrational assignments and structure.

Vibrational spectra of penta‐atomic silicon–carbon clusters. II. Linear Si2C3

The geometry and vibrational spectrum of the previously not studied silicon–carbon cluster Si2C3 has been investigated Geometries and frequencies for a number of isomeric structures are presented at the Hartree–Fock level In agreement with a concurrent experimental observation the ground state is found to be linear Harmonic frequencies, isotopic shifts, and infrared intensities calculated using many‐body perturbation theory to second order are found to be in good agreement with the experimental results supporting the identification of a new penta‐atomic silicon–carbon cluster The general behavior of penta‐atomic silicon–carbon clusters is discussed and preliminary ground state geometries and harmonic frequencies are presented for Si3C2 and Si4C

An ab initio study of the structure and infrared spectrum of Si2C3

Prediction of Electrolyte Conductivity: Results from a Generalized Molecular Model Based on Ion Solvation and a Chemical Physics Framework

A Fourier transform infrared (FTIR) study has resulted in the first identification of a fundamental vibration of SiC4, the ν1, C■C stretching mode at 20801 cm−1 SiC4 was produced by trapping in Ar at 10 K the products of the vacuum ultraviolet (VUV) photolysis of silane (SiH4) and 1,3‐butadiene (C4H6) or the products from the evaporation of a mixture of Si and C powder The vibrational assignment is confirmed by 13C ‐isotopic data for 20 isotopomers, which is in excellent agreement with the predictions of ab initio calculations

P. A. Withey

Papers

Vibrational spectra of penta‐atomic silicon–carbon clusters. I. Linear SiC4 in Ar at 10 K