Edge energy calculations in Al and Ni ultra-thin nanowires by molecular dynamics simulations

Abstract

Cohesive energy of metallic nanowires is strongly related to the energetic cost associated to surfaces and edges. In this work equilibrium configurations of aluminum and nickel FCC nanowires are studied in order to determine the edge energy associated to several different edge configurations. The T=4K equilibrium configurations of the nanowires under study are obtained by means of a molecular dynamics optimization of the cohesive energy as a function of nanowire strain. The cohesive energy is computed using Embedded Atom Method (EAM) semi-empirical potentials. We define an equation of state, which describes the nanowire cohesive energy for different radii as a balance between bulk cohesive energy and the (negative) surface and edge energies associated to the different exposed atoms. From this equation of state we are able to determine the edge energies for different edge geometries. Our simulations show that atomic rearrangements take place at the edge positions. These rearrangements contribute to decrease the energetic cost of these low coordinated configurations.