Stability of the binary colloidal crystals AB2 and AB13 -: art. no. 031407

Suspensions of binary mixtures of hard-sphere poly-methylmethacrylate colloidal particles were studied at six different size ratios alpha. The main aim was to determine the range of size ratios over which the binary colloidal crystals AB(2) and AB(13) are stable. Combining these results with those of earlier work, we found stability of AB(2) for 0.60 greater than or similar to alpha greater than or similar to 0.425, in good agreement with theoretical predictions by computer simulation and cell model methods. AB(13) was observed for 0.62 greater than or similar to alpha greater than or similar to 0.485, the lower limit being significantly smaller than the theoretical prediction of about 0.525. Rough measurements of crystallization rates showed that AB(2) tended to crystallize fastest at small size ratios, whereas the opposite was true for AB(13). These findings should provide a guide to the optimum conditions for materials applications of these binary colloidal crystals.