Finite Temperature Behavior of Gas Phase Neutral Au_<i>n</i> (3 ≤ <i>n</i> ≤ 10) Clusters: A First Principles Investigation

Abstract

Relativistic density functional theory (DFT) based molecular dynamical simulations are performed on gold clusters with 3–10 atoms (Aun, n = 3–10) with an aim of understanding their finite temperature behavior. Conformations of a cluster coexisting at different temperatures are analyzed. The simulations reveal that the finite temperature behavior of Au clusters can be classified into three regions, viz., a “solid-like” region, a “structural fluctionality” region, and a “liquid-like” state. The structural fluctionality region is when the cluster dynamically interconverts between two conformations through a metastable intermediate. For Aun, n ≤ 7, where the atoms reorient continuously such that two planar conformations coexist. On the other hand, for Aun, n ≥ 8, the cluster behaves as a quasi-planar liquid where the outer edge atoms of the cluster bend and relax alternatively around a central planar region. In liquid-like state the cluster is predominantly in a 3D conformation and transits through various conformations. The onset and duration of each of the above three regions are seen to be size dependent. Au6 is the most stable cluster and remains in its ground state conformation (or solid-like region) up to nearly 1100 K. Au9 is the least stable among the studied clusters with a liquid-like state around room temperature itself. All the clusters with the exception of Au6 enter the liquid-like state at much lower temperatures as compared to that of bulk gold.