Vibrational spectra obtained from high quality potential energy surfaces spanned by low level normal coordinates: application to CHFClI and CDFClI

Abstract

The impact of approximate normal coordinates for spanning high level potential energy surfaces on vibrational frequencies is studied within the framework of vibrational SCF and configuration interaction calculations (VCI). The use of low level normal coordinates avoids expensive geometry optimizations and harmonic frequency calculations and thus allows for a significant reduction in CPU time. Benchmark calculations are provided for a set of molecules ranging from 5 to 7 atoms. An application to CHFClI and CDFClI shows that this approximation still allows for very accurate results. These molecules are of particular interest for studying parity violation effects.

Acknowledgements

This work was performed within the Collaborative Research Centre SFB 706 (Selective Catalytic Oxidations Using Molecular Oxygen; Stuttgart) and funded by the German Research Foundation. The authors thank Professor P. Botschwina for helpful discussions and Dr J. Crassous for a copy of the Raman spectrum of CHFClI. P. Schwerdtfeger acknowledges financial support from Marsden fund and the ISAT Linkage fund (Wellington).