Diffusion as a Cause of Heat Capacity Growth of Nanocrystalline Palladium

Using molecular dynamics method the heat capacity of ideal fcc palladium clusters of 6 nm in diameter has been investigated in the temperature range from 150 to 300 K. At 150 K the value obtained for palladium nanoparticles exceeds that of the corresponding bulk material by 12–16%. It was also found that the difference becomes less noticeable under growing the temperature. To explain the disagreement of our results with the available experimental data on compactificated palladium additional investigations were carried out on palladium clusters with the density corresponding to 80% of the bulk value. On the basis of the simulation results a conclusion has been made that the growth of the heat capacity of compactificated materials is not determined by growing the heat capacity of separate clusters. In all probability, the nature of the significant overestimation of the heat capacity of compactificated nanomaterials relates to their disordered state.