On the existence of SH₃, SeH₃, and TeH₃: Discrepancies between all‐electron and pseudopotential calculations

Abstract

Abstract Ab initio calculations using both pseudopotential and double and triple‐ζ all‐electron basis sets, with and without electron correlation (MP2, QCISD), have been performed on the λ 4 ‐sulfanyl (SH 3 ), λ 4 ‐selanyl (SeH 3 ), and λ 4 ‐tellanyl (TeH 3 ) radicals. All‐electron basis sets of double‐ζ quality predict that SH 3 and SeH 3 correspond to transition states on their respective potential energy surfaces. In contrast, the pseudopotentials of Hay and Wadt predict that SH 3 and SeH 3 correspond to local minima at the QCISD level of theory while the pseudopotentials of Christiansen and Stevens predict transition states. By comparison, TeH 3 proved to be a local minimum at all levels of theory. Interestingly, when a very large (triple‐ζ) all‐electron basis set was used, SH 3 proved to be a transition state; however, in this instance the potential energy surface was found to be much flatter than in the case for which a double‐ζ basis set was used, suggesting that further improvements in the basis set may lead to a local minimum. Further improvements in the all‐electron selenium basis also led to a local minimum for SeH 3 at the QCISD level of theory. © 1995 by John Wiley & Sons, Inc.