A comparison between crystallographic and theoretical structures for three hypervalent RSnCl(3) compounds

Three compounds of the general formula RSnCl₃, where R contains an additional potential donor atom (i.e. O or Cl), have been subjected to ab initio geometry optimisation calculations. The interatomic parameters of the optimised geometries (calculated using Hartree-Fock (HF) theory, Density Functional Theory (DFT) and hybrid HF/DFT (B3LYP) theories, each employing the LanL2DZ basis set) are compared with previously determined crystallographic results. The study shows that Sn...O hypervalent interactions persist in the theoretical gas phase structures emphasising the chemical importance of such interactions. By contrast, intramolecular Sn...Cl interactions seen in the solid state do not persist in the theoretical structures suggesting that these may arise as a result of crystal packing effects

The Australian Chemistry Enhanced Laboratory Learning Project: Catalysing Effective Laboratory-Based Teaching and Learning

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Discrete Component Analysis

This article presents a unified theory for analysis of components in discrete data, and compares the methods with techniques such as independent component analysis, non-negative matrix factorisation and latent Dirichlet allocation. The main families of algorithms discussed are a variational approximation, Gibbs sampling, and Rao-Blackwellised Gibbs sampling. Applications are presented for voting records from the United States Senate for 2003, and for the Reuters-21578 newswire collection