Evaluation of the performance of the HCTH exchange-correlation functional using a benchmark of sulfur compounds

The performance of the exchange-correlation density functional HCTH has been assessed using a benchmark of sulfur-containing molecules. Optimised structural parameters, harmonic frequencies and atomisation energies are presented and compared with calculations using the BLYP density functional, the MP2 methodology and appropriate experimental results. It is shown that, for sulfur compounds that do not contain halogens, the HCTH functional predicts geometries that are comparable to both the MP2 method and experiment, and harmonic frequencies are in much closer agreement with experiment than either the BLYP or MP2 methods; the atomisation energies are predicted within a few kcal mol-1 of the calculated MP2 results. The performance regarding sulfur-halogen compounds needs to be improved by the inclusion of F2S and Cl2S into the training set of future HCTH functionals.