Exploring the potential energy surface of Au55 magic cluster to study thermodyn properties

Abstract

For the large size nanoclusters (equivalent diameter of 1.0 nm to 4.0 nm), finding the global minimum (GM) is a major challenge in chemistry, physics and biosciences due to high computational cost required to explore their potential energy surface (PES). The structure, reactivity, properties and spectra of the chemical system can be easily studied with the help of PES. Herein, we have done the PES fitting using two body function i.e. spherical harmonics based descriptor integrated with artificial neural network (ANN). We have performed the molecular dynamics (MD) simulations and GM optimization for Au55 by using ANN and found that the GM is an amorphous molecular structure rather than icosahedron geometry (ICO). Using DFT, we have confirmed that the predicted GM is 2.22 eV lower in energy than ICO. The predicted GM consists of 8 atoms in the core and 47 atoms on the surface. A brief study on fluxional nature and probability of low-lying isomers of Au55 is performed and it is concluded that Au55 has a dynamic surface which can be helpful in the study of reaction dynamics. Also, GM structure is stable up to a high temperature of 750 K.