A comparative study on the twinning boundaries of five-fold twinned copper and gold nanorods

Abstract

Five-fold twinned copper and gold nanorods are important materials in heterogeneous catalysis. However, knowledges on the twinning boundary structures and their catalytic activities are quite limited. In this work, we conducted large-scale structure searching on the basis of forcefield potential and evolutionary algorithm, and precise quantum calculations on electronic structures and chemisorption energies using first-principles density functional theory. We determined the optimal twinning structures of the five-fold twinned copper and gold nanorods and analyzed their geometric differences via computing the standard deviation of metal bond lengths and the degrees of order. It was found that Au twinning boundary has a generally more regular structure but could involve noticeable point or line defects in some local areas, whereas Cu shows an incompact structure with fewer defects in the twinning region. Further by surface adsorption calculations using probe molecules of benzene and CO2, we show different degrees of chemisorption enhancement at various sites in or beside the twinning boundaries. Together with calculated charge transfer between adsorbates and metals or among different twinning regions, our results may provide some useful insights into the structural and chemisorption characteristics of twinned nanomaterials.