Melting of the Au₂₀ Gold Cluster: Does Charge Matter?

We investigate the dependence upon the charge of the heat capacities of magic gold cluster Au₂₀ obtained from density functional-based tight binding theory within parallel tempering molecular dynamics and the multiple histogram method. The melting temperatures, determined from the heat capacity curves, are found to be 1102 K for neutral Au₂₀ and only 866 and 826 K for Au₂₀⁺ and Au₂₀^-. Both the canonical and the microcanonical aspects of the transition are discussed. A convex intruder, associated with a negative heat capacity, is evidenced in the microcanonical entropy in the case of the neutral cluster but is absent in the melting processes of the ions. The present work shows that a single charge quantitatively affects the thermal properties of the gold 20mer.