  A general Monte Carlo simulation method of calculating the elastic constants
of polydisperse hard-sphere colloidal crystal was developed. The elastic
constants of a size polydisperse hard sphere fcc crystal is calculated. The
pressure and three elastic constants(C11, C12 and C44) increase significantly
with the polydispersity. It was also found from extrapolation that there is a
mechanical terminal polydispersity above which a fcc crystal will be
mechanically unstable.
