Formation of regular polyicosahedral and defected crystalline structures in growing Lennard-Jones clusters

Abstract

Formation of solid structure and its subsequent enlargement have been analysed in simulated growth of Lennard-Jones (LJ) clusters from vapour. Four series of the Monte Carlo simulations, carried out for constant temperature T⁎=0.25, 0.30, 0.35 and 0.40 in reduced units, were started from LJ13 icosahedral cluster used as a seed in a supersaturated LJ vapour. In the first simulation stage, all the 504 simulated clusters (over 100 growth runs for every analysed temperature) achieved the size N≈1000. Structural analysis and visualisation showed that at this size many of the obtained clusters (i.e. 10%, 29%, 34% and 66%, respectively, for the above temperatures) were well ordered. They were found to have regular internal structure mainly of regular polyicosahedral and layered fcc/hcp structure. In the second simulation stage practically all the obtained clusters were grown until N=3300 was reached, while in the third stage the selected regular structures attain N=9800. Visualisation of the internal structure of the growing regular clusters from their solidification up to the final size N≈9800 revealed that (i) the layered fcc/hcp structure maintains layered character if fcc layers are relatively thin, and (ii) r-PIC clusters initially keep the structure during the growth, but its subsequent growth leads to the formation of disordered regions.