Equilibrium structure and vibrational spectra of sila-adamantane

TL;DR

This study investigates the electronic and vibrational properties of sila-adamantane, a silicon analogue of adamantane, using density functional theory, revealing structural and spectral differences from its hydrogenated counterpart.

Contribution

It provides the first detailed computational analysis of sila-adamantane's electronic structure and vibrational spectra, comparing it with the silicon analogue Si10H16.

Findings

Sila-adamantane has an expanded Si10 core compared to Si10H16.

The vibrational spectra show numerous peaks due to ligand substitution.

The Si-C stretch at 664 1/cm matches recent experimental measurements.

Abstract

The recent synthesis of a four-fold silylated sila-adamantane molecule (C$_{24}$H$_{72}$Si$_{14}$, T$_d$), [J. Fischer, J. Baumgartner, and C. Marschner, {\it Science} {\bf 310,} (2005) 825] is the first attempt of making the silicon analogue of adamantane. It has adamantane-like Si$_{10}$ core, capped by methyl and sily-methyl ligands. We report its electronic structure, vibrational spectrum, and the infra-red and Raman spectra calculated within the density functional formalism using large polarized Gaussian basis sets. The properties of sila-adamantane are compared with exact silicon analogue Si10H16 of adamantane. Results show that replacing hydrogens in Si10H16, by methyl and silymethyl ligands results in expansion of the Si10 core and results in large number of peaks in the Raman spectrum. The Si-C stretch at 664 1/cm and methyl deformations frequencies compare well with recent measurements of vibrational frequencies of methylated silicon surface.