Structures of ultrathin copper nanotubes

Abstract

We have performed atomistic simulations for helical multi-shell (HMS) Cu nanowires and nanotubes. Our investigation on HMS Cu nanowires and nanotubes has revealed some physical properties that were not dealt with in previous works that considered metal nanowires. As the diameter of HMS nanowires increases, their cohesive energy per atom decreases but their optimal lattice constants are almost constant. Shell-shell or core-shell interactions mainly affect the lattice constant and the diameter of HMS nanowires or nanotubes. Our molecular dynamics simulations show that parts of ultrathin Cu nanotubes collapse into the empty core at low temperature and this is the main mechanism for the transformation from ultrathin nanotube to nanowire structures. This study shows that HMS Cu nanotubes can retain their own structures when the internal stresses on HMS nanotubes are zero or towards the outside.