H(3) (+) as a trap for noble gases--2: structure and energetics of XH(3) (+) complexes from X=neon to xenon.

The affinity of H(3) (+) to combine with noble gases X has been investigated from neon to xenon using ab initio coupled cluster [CCSD and CCSD(T)] and density functional BH&HLYP levels of theory. For all noble gases, the stable structures belong to a C(2v) symmetry with an apex of the H(3) (+) triangle pointing to the noble gas. The structure of the complexes changes gradually from a practically pure Ne-H(3) (+) arrangement to a situation close to XeH(+)-H(2). A topological analysis of the electron localization function is used to illustrate the changes in the bonding along the series. The lowest dissociation energies of NeH(3) (+) and ArH(3) (+) ( approximately 1 and approximately 7 kcalmol) correspond to the breaking of the complexes according to X+H(3) (+), while the lowest dissociation energies of KrH(3) (+) and XeH(3) (+) ( approximately 8 and approximately 3 kcalmol) correspond to the breaking according to XH(+)+H(2). Rotational constants and harmonic frequencies are reported. Apart from XeH(3) (+) whose dipole moment (mu=2.6 D) may not be large enough, all the other complexes with dipole moments in the range of 6-8 D should be reasonable targets for detection by microwave spectroscopy. The present calculations are intended to stimulate both laboratory experiments and spatial observations since the possible sequestration of noble gases by H(3) (+) may have strong implications on the composition of astrophysical objects.