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 He2Xn+ (where X=B–Ne, Al–Ar and n=1–3) were studied using the CCSD(T) method 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 highest level of theory employed, the CCSD(T)_FC/cc-pVQZ model, was used to elucidate trends in bond lengths, dissociation energies and harmonic frequencies. The more highly charged species were found to have shorter bond lengths than the singly charged species. The ground states of the helide cations were often those with longer bond lengths when compared with the excited state ions.