Dependence of self-diffusion coefficient, surface energy, on size, temperature, and Debye temperature on size for aluminum nanoclusters

Molecular dynamics simulations are performed to investigate the surface energy and self-diffusion coefficient in aluminum nanoclusters (AlN) as a function of temperature, T (T = 300–1100 K), and size (N = 108–4000 atoms, with N the number of atoms in the cluster), with the self-diffusion coefficient compared with the bulk limit. Debye temperature, cohesive energy, and average coordination number of AlN are also explored as a function of the cluster size. The surface energy decreases as a function of size as well as temperature, and becomes very small at sizes larger than N ≥ 2000, while the average coordination number and the Debye temperature increase as a function of nanocluster size. The self-diffusion coefficient decreases with increasing size as N−2/3, while increasing as a function of temperature, and exhibits values substantially larger than in the bulk, quantitatively confirming the much greater structural freedom encountered of nanoscale systems.