Theoretical study of the thermally induced structural fluctuations in sub-nanometre size gold clusters

Abstract

A reactive potential model and the classical molecular dynamics method (RMD) have been used to study the structure and energetics of sub-nanometre size gold clusters through well-known structural models reported in the literature for AuN ,w ithN = 19, 20 and 21 atoms. After several simulated-annealing simulations for temperatures up to 1500 K, the AuN clusters clearly evolve to well-defined structures at room temperature. For the studied gold clusters, the low-lying structures are single- and double-icosahedra with mobile atoms on the surface, in agreement with experimental results on sub-nanometre size gold clusters exhibiting shape oscillations at room temperature and also with those involved in the design of molecules based on gold superatoms (J.-I. Nishigaki, K. Koyasu, T. Tsukuda, Chem. Rec. 14, 897 (2014)). The evolution of the structural stability of the AuN clusters under exceptional thermal conditions is analysed by comparing the size and temperature variations of the centrosymmetry parameter and the potential energy. A key understanding of the various possible structural changes undergone by these tiny particles is thus developed. The usefulness of the RMD to study nanometre or sub-nanometre size gold clusters is shown.