A molecular-dynamics study of thermal and physical properties of platinum nanoclusters

Metallic nanoclusters are interesting because of their utility in catalysis and sensors. The thermal and physical characteristics of metallic Pt nanoclusters with different sizes were investigated via molecular-dynamics simulations using Quantum Sutton-Chen (QSC) potential. This force field accurately predicts solid and liquid states properties as well as melting of the bulk platinum. Molecular dynamic simulations of Pt nanoclusters with 256, 456, 500, 864, 1372, 2048, 2916, 4000, 5324, 6912, 8788 atoms have been carried out at various temperatures. The Pt-Pt radial distribution function, internal energy, heat capacity, enthalpy, entropy of the nanoclusters were calculated at some temperatures. These properties are used to characterize the physical phase and also to determine the melting transition of each nanocluster. The melting point predicted by the various properties is consistent with each other and shows that the melting temperature increases with the particle size, approaching to the bulk limit for the largest one. The size dependence of the melting point has been reported, both experimentally and theoretically for the atomic nanoclusters. We have found that the melting of the platinum nanoclusters commences at the surface and the relation T m , N = T m , bulk − α N − 1 / 3 between the melting point of nanocluster (Tm,N) and that of the bulk (Tm,bulk) holds. The extrapolation of Tm,N versus N−1/3 gives Tm,bulk = 2058.1 K which is in a good agreement with the experimental value of 2041 K.