Molecular dynamics simulation of metal cluster cooling and heating in noble gas atmosphere

Metal cluster properties such as ionization potential and reactivity strong ly depend on the temperature of the cluster. Using molecular dynamics simul ation we have investigated how much energy is transferred from noble gas at oms to unsupported Pd-13 clusters in collisions. Furthermore we propose a t wo-term density of states for Pd-13 which leads to excellent prediction of the caloric equation of state obtained in simulations. Knowing the heat cap acity of the cluster, the energy transfer can be converted into change of c luster temperature per collision at constant gas temperature and the coolin g and heating of the cluster can be predicted. The predictions were in good agreement with cooling and heating simulations. Approximately 2000 collisi ons are required to cool Pd-13 from 1500 K to 100 K in a helium gas at 100 K. (C) 1999 Acta Metallurgica Inc.