THE POTENTIAL-ENERGY SURFACE AND VIBRATIONAL-ROTATIONAL ENERGY-LEVELSOF HCP

The potential energy surface of phosphaethyne, HCP, has been determine d from large-scale ab initio calculations using the coupled-cluster me thod, CCSD(T), with basis sets of triple- to quintuple-zeta quality. T he vibrational-rotational energy levels of the HCP molecule have then been calculated using the variational method and have been further cha racterized by the spectroscopic constants determined using the perturb ational approach. The effects of the one-particle basis set and of cor e correlation on the calculated molecular parameters have been investi gated. The spectroscopic constants determined at the most advanced lev el of theory used here are found to be in excellent agreement with exp erimental data. (C) 1997 Elsevier Science B.V.