Ab initiostudy of linear atomic chains in copper nanowires

Abstract

Recently experimental and theoretical results established that copper nanowires (NWs) evolve to form linear atomic chains when pulled along the [100], [110], and [111] crystallographic directions. Since that, copper NWs became an exciting alternative to produce nanocontacts. In the present study, we used ab initio calculations based on density-functional theory within the local density and generalized gradient approximations to investigate the electronic structure of copper NWs obtained from previous tight-binding molecular dynamics (TBMD) simulations. The TBMD structures obtained just before rupture were used for the ab initio calculations. By pulling the NWs quasistatically in these cases, we also observed their breaking at similar distances as in the TBMD, regardless of the exchange-correlation potential used. The pulling forces before rupture were also presented for TBMD and ab initio calculations and they are in good agreement. Finally, we present a detailed analysis of the electronic structure of selected atoms from the NWs linear atomic chains and tips before rupture. Our results show that the electronic properties are bulklike for atoms with coordination six or more. However, lower coordinated atoms from tips and linear atomic chains have their electronic properties characterized by sharper $d$ and $s$ states shifted toward the Fermi energy.