Does hydrogen pre-melt palladium clusters?

We use molecular dynamics simulations to study the influence of an ambient atmosphere on the melting process in the icosahedral palladium clusters Pd13, Pd55 and Pd147. Novel methods to capture the character of melting in finite systems are presented. The signature of melting in clusters heated by inert carrier gas collisions closely resembles that in systems heated in a Nosé-Hoover thermostat. Exposure to hydrogen instead of an inert carrier gas, however, significantly lowers the melting temperature.