Grain size effects on lateral islands in hard-sphere crystals

Due to the lateral stacking disorder, random hexagonally closed- packed hard- sphere crystals consist of lateral islands with different lateral positions A, B, and C, and as a consequence, different stacking. We investigate the extent of lateral stacking disorder as a function of grain size, and as a function of the fraction of FCC- stacked particles a by laser scanning confocal microscopy and Monte Carlo simulations. We compare the simulations and microscopy data to relate stacking islands ( 2D domains with identical stacking type and direction) to lateral islands. Small crystals mainly contain single hexagonal planes, whereas larger crystals consist of a much larger number of lateral islands. Furthermore, the typical stacking island size is related to the FCC fraction. At high a, more FCC islands nucleate, and these are more likely to combine into larger islands than the HCP islands.