Preference for fcc atom stacking observed during growth of defect-free LJ3281 clusters

Growth simulations of 3-dimensional Lennard-Jones (LJ) clusters/nuclei from the vapor phase were carried out in order to estimate the role of kinetic and energetic effects in determining the internal structure of the clusters. The simulated growth was realized from N = 3281 up to ca. 10000 atoms at two reduced growth temperatures T* = 0.3 and 0.5 and the vapor atom concentration n(v) = 0.002 (in reduced units of LJ system). During growth at the low temperature, clusters evolve from octahedral to an irregular shape, while at the higher one they become spherical. Statistics of newly created structural units shows a strong preference for the formation of fcc units with their number approximately 3-4 times larger than those of the hcp units. The possible explanation of this preference is by: (1) a larger surface diffusion leading to near spherical shape of clusters, (2) an energetic effect caused by different interaction energy of two fcc or hcp layers located on the neighboring {111} planes, and (3) an entropic effect in the form of disappearance of hcp island on the close-packed fcc layers. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.