Structure and stability of Na+Xen clusters

Abstract

The structure and stability features of Na+Xe n (n ≤ 54) clusters are theoretically investigated via model potential energy surfaces (PES) and unconstrained global optimization. The potential energy is described in terms of pair-additive potentials including polarization parametrized from accurate ab initio data on Na+Xe, complemented by three-body contributions describing the interaction between the dipoles induced by the sodium ion on the rare gas atoms. We show that the three-body contributions stabilize the linear or planar structures versus more compact shapes for n< 4. At larger sizes, the growth around the square antisprism (SA) or capped square antisprism (CSA) core is favored while icosahedral pattern based isomers exist but not as the lowest ones. A transition in the metal ion coordination from 8 (square antiprism) to 12 (icosahedron) is seen to occur near n = 50. The results are discussed and analyzed in view of existing accurate ab initio calculations on Na+Xe2 and comparisons with similar metal-ion clusters.