PNNL

Abstract

Twin structures possess distinct physical and chemical properties by virtue of their specific twin configuration. However, twinning and de-twinning processes are not fully understood at the atomic scale. Integrating in situ high resolution transmission electron microscopy and molecular dynamic simulations, we find tensile strain in the asymmetrical five-fold twins of Au nanoparticles leads to twin boundary migration through dislocation sliding along twin boundaries and dislocation reactions at the five-fold axis under an electron beam. Migration of one or two layers of twin planes corresponds to one energy barrier, but overall the total energy, including surface, lattice strain, and twin boundary energy, is relaxed after consecutive twin boundary migration, leading to a detwinning process. In addition, surface rearrangement of five-fold twinned nanoparticles can aide in the de-twinning process.