Negative heat capacity of sodium clusters

Abstract

Heat capacities of Na_N, N = 13, 20, 55, 135, 142, and 147, clusters have been investigated using a many-body Gupta potential and microcanonical molecular dynamics simulations. Negative heat capacities around the cluster melting-like transition have been obtained for N = 135, 142, and 147, but the smaller clusters (N = 13, 20, and 55) do not show this peculiarity. By performing a survey of the cluster potential energy landscape (PEL), it is found that the width of the distribution function of the kinetic energy and the spread of the distribution of potential energy minima (isomers), are useful features to determine the different behavior of the heat capacity as a function of the cluster size. The effect of the range of the interatomic forces is studied by comparing the heat capacities of the Na_55 and Cd_55 clusters. It is shown that by decreasing the range of the many-body interaction, the distribution of isomers characterizing the PEL is modified appropriately to generate a negative heat capacity in the Cd_55 cluster.

7 pages, 5 figures, Accepted in Physical Review B

Cited by in corpus (12)

• Geometric magic numbers of sodium clusters: Interpretation of the melting behaviour
• Violation of the Zeroth Law of Thermodynamics in Systems with Negative Specific Heat
• Identifying structural patterns in `disordered' metal clusters
• Melting of aluminium clusters
• On the premelting features in sodium clusters
• Impurity effects on the melting of Ni clusters
• Effect of finite-size heat source's heat capacity on the efficiency of heat engine
• Super-statistical description of thermo-magnetic properties of a system of 2D GaAs quantum dots with gaussian confinement and Rashba spin-orbit interaction
• A generalized quantum microcanonical ensemble
• The electronic structures, the equilibrium geometries and finite temperature properties of Na_n (n=39-55)
• Squeezed ensemble for systems with first-order phase transitions
• Statistical ensembles for phase coexistence states specified by noncommutative additive observables