  Disappearance of a stacking fault in the hard-sphere crystal under gravity,
such as reported by Zhu et al. [Nature 387 (1997) 883], has successfully been
demonstrated by Monte Carlo simulations. We previously found that a less
ordered (or defective) crystal formed above a bottom ordered crystal under
stepwise controlled gravity [Mori et al. J. Chem. Phys. 124 (2006) 174507]. A
defect in the upper defective region has been identified with a stacking fault
for the (001) growth. We have looked at the shrinking of a stacking fault
mediated by the motion of the Shockley partial dislocation; the Shockley
partial dislocation terminating the lower end of the stacking fault glides. In
addition, the presence of crystal strain, which cooperates with gravity to
reduce stacking faults, has been observed.
