Melting and Structural Evolution of Palladium and Graphite-supported Palladium Nanoclusters: A Molecular Dynamics Simulation Study

The thermal behavior of palladium nanoclusters of different sizes, in free space and on a graphite surface, was studied using molecular dynamics simulations. The Sutton-Chen many-body potential function was utilized for the metal, and the structured graphite surface was represented by a simple Lennard-Jones model. Changes in thermodynamic and structural properties upon heating and cooling in the temperature range of 300 K to 1400 K were studied. Melting (and wetting, in the graphite-supported case) behavior was characterized by calculating a number of thermodynamic, structural and dynamic properties. Surface melting was found in both cases which developed into the bulk. The energy transfer mechanisms between the pre-melted surface and solid core was studied through calculations of diffusion coefficients in radial shells and the calculation of velocity auto-correlation functions of the atoms in each of these shells.