Abnormally high melting temperature of the Sn₁₀ cluster

Abstract

We study the melting of the Sn₁₀ cluster with ab initio isokinetic molecular dynamics. The electron localization function is used to probe the bonding character, which is found to be covalent. We use the multiple-histogram technique to calculate the ionic entropy and specific heat, from a total simulation time of more than 2 ns. The specific heat shows a shoulder around 500 K due to a permutational rearrangement of atoms that preserves the trigonal prism core of the ground state. Only at much higher temperatures T≳1500K does this core distort and break up, yielding a peak in the specific heat around 2300 K. These findings suggest a natural explanation for the recently observed high melting temperatures of small Sn clusters.