Size-depressed critical temperatures for the order-disorder transition of FePt, CoPt, FePb, Cu2S, and ZnS nanostructures

► We expound size effect on the phase transition temperature of two type nanomaterials. ► Phase transition temperature is proportional to the mean cohesive energy of atoms. ► Size dependence of transition temperature originates from undercoordination atoms. ► Undercoordination atoms at the surface induce the loss in cohesive energy. ► The size induced trend is determined by the skin-to-body volume ratio.