Semiempirical study of rare gas and rare gas–hydrogen ionic clusters: R+<i>n</i>, (R<i>n</i>H)+, and (R<i>n</i>H2)+ for R≡Ar, Xe

Abstract

The ionic rare gas clusters Ar+n and Xe+n and rare gas–hydrogen clusters (ArnH)+, (ArnH2)+, (XenH)+ and (XenH2)+ are studied by the semiempirical diatomics-in-ionic-systems (DIIS) method. The Ar+n clusters (n&amp;gt;3) are seen to have a structure of a linear Ar+3 core surrounded by n−3 neutral or almost neutral Ar atoms. For Xe+n (n&amp;gt;3), a symmetrical Xe+4 ionic core with the geometry of regular pyramid is formed. The rare gas–hydrogen clusters with one H atom have a simple Rk(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 ArnH+2 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.