Anharmonic vibrational spectroscopy calculations for novel rare-gas-containing compounds: HXeH, HXeCl, HXeBr, and HXeOH

A first-principles calculation of vibrational spectroscopy of HXeH, HXeCl, HXeBr, and HXeOH molecules is performed by combining ab initio codes with t he vibrational self-consistent field (VSCF) method, and with its extension by perturbation theory (CC-VSCF). The MP2/CC-VSCF method is anharmonic, and it is able to reproduce the experimentally observed spectral features of H XeH, HXeCl, HXeBr, and HXeOH. The most intense bands of the HXeY molecules, the Xe-H stretching modes, are found to be highly anharmonic. In general, the other fundamental modes presented anharmonic effects to a lesser extent . New predictions of overtone and combination vibrations are made to help e xperimental investigations of these molecules. It is shown that vibrational spectroscopy calculations are reliable and useful for analyzing the spectr al features of rare-gas-containing molecules. While the results of the MP2/ CC-VSCF calculations are in much better agreement with experiments than the corresponding harmonic frequencies, substantial discrepancies remain. Thes e are mostly due to the large electronic correlation effects in these syste ms, which are not sufficiently well presented at the MP2 level.