Inner Energy Relaxation and Growth of Nano-Size Particles

Abstract

In this study, molecular dynamics simulations were conducted to investigate the relaxation of the internal energy in nano-sized particles and its impact on the nucleation of atomic clusters. Quantummechanical potentials were utilized to analyze the growth and collision relaxation of the internal energy of ArnH + clusters in a metastable Ar gas. The results revealed that small nano-clusters are formed in highly excited rotational-vibrational states, and the relaxation of internal energy and growth of these nascent clusters are concurrent processes with a strong mutual influence. Under nonequilibrium growth conditions, the relaxation of internal energy can delay the cluster growth process. The rates of cluster growth and internal energy relaxation were found to be influenced by energytransfer collisions between cluster particles and free Ar atoms of the bath gas. Furthermore, the non-equilibrium growth and internal energy relaxation of small nano-clusters were found to depend on the structure of the cluster's atomic shells. An ensemble of molecular dynamics simulations were conducted to investigate the growth, time-evolution of kinetic and total energies of ArnH + clusters with specified n ≤ 11, and the results were explained by collisional relaxation processes described by the Boltzmann equation. Finally, the general relationship between the rates of internal energy relaxation and non-equilibrium growth of nano-particles is discussed.