Ab initio investigation of the electronic structure and stabilities of triatomic helide ions: He2Xn+ clusters (where X = B-Ne, Al-Ar and n = 1-2)

The electronic structure and molecular properties of helides of the form He 2Xn+ (where X = B-Ne, AI-Ar and n = 1-3) were studied using the CCSD(T) met hod in conjunction with the series of correlation-consistent basis sets of descending in quality from cc-pVQZ, aug-cc-pVTZ, cc-pVTZ to cc-pVDZ. The hi ghest level of theory employed, the CCSD(T)_FC/ccpVQZ model, was used to el ucidate trends in bond lengths, dissociation energies and harmonic frequenc ies. The more highly charged species were found to have shorter bond length s than the singly charged species. The ground states of the helide cations were often those with longer bond lengths when compared with the excited st ate ions. (C) 1999 Elsevier Science BV. All rights reserved.