SEMIEMPIRICAL STUDY OF RARE-GAS AND RARE-GAS HYDROGEN IONIC CLUSTERS - AR-N+, XE-N+, (ARNH)+, (XE-NH+), AND (AR-NH-2)+, (XE-NH-2)+

The ionic rare gas clusters Ar(n)+ and Xe(n)+ and rare gas-hydrogen clusters (Ar(n)H)+, (Ar(n)H2)+, (Xe(n)H)+ and (Xe(n)H2)+ are studied by the semiempirical diatomics-in-ionic-systems (DIIS) method. The Ar(n)+ clusters (n > 3) are seen to have a structure of a linear Ar3+ core surrounded by n - 3 neutral or almost neutral Ar atoms. For Xe(n)+ (n > 3), a symmetrical Xe4+ ionic core with the geometry of regular pyramid is formed. The rare gas-hydrogen clusters with one H atom have a simple R(k) (RH)+ structure with k neutral rare gas atoms attracted to the (RH)+ molecule by polarization forces. Two H atoms can bind with Ar atoms to form quasistable clusters Ar(n)H2+ which dissociate to (n - 1) Ar + H + (ArH)+ through a high barrier of roughly 0.75 eV. Two H atoms and one Xe+ ion are shown to form a collinear valence-bound (XeHH)+ cluster whose dissociation energy is 0.46 eV.