Cohesive energy and surface energy of fcc metallic nanocrystals

The model for the surface energy of fcc metallic nanoparticles is developed based on the model for size-dependent cohesive energy and surface bond deficit consideration for the nanoparticles. Firstly, through the study the surface/volume ratio and surface CN(coordinate number) of the Wulff structure, the cohesive energy of interior atoms is determined. It is found that as same as the cohesive energy for the whole particles, the cohesive energy of interior atoms also decrease with the decreasing size. Considering the weakness of the cohesive energy and the increase of the surface bonds defect, size dependent surface energy of fec metallic nanoparticles is determined. It is found that the surface energy have reduction firstly and turn back to increase when the size approach to critical size of particles. The reduction of surface energy is mainly due to the decrease of cohesive energy. The following increase of surface energy is due to the decrease of surface CN. Our prediction for the surface energy is agreed with the simulation results for metallic nanoparticles.