The effects of electronic structure and charged state on thermodynamic properties: an ab initio molecular dynamics investigations on neutral and charged clusters of Na₃₉, Na₄₀, and Na₄₁

Abstract

In this paper we explore the effects of the electronic structure, the charge state, and the nature of energy distribution of isomers on the thermodynamic properties of sodium clusters. The focus of the work is to isolate the effects of these ingredients on thermodynamic behavior by choosing specific clusters. Toward this end we investigate Na₃₉^-, Na₄₀, and Na₄₁⁺, which are the electronic closed shell systems which differ in number of atoms and charge state. We also examine Na₃₉, Na₃₉⁺, Na₄₀⁺, and Na₄₁ clusters having different charges of these clusters. Our density functional molecular dynamics simulations show that all electronic shell-closing clusters have similar melting temperature of ≈ 310 K. Remarkably, it is observed that an addition of even one electron to Na₃₉ increases the melting temperature by about 40 K and makes the specific heat curve sharper. All the cationic clusters show broadened specific heat curves.