SELF-ASSEMBLY DRIVEN CRYSTALLIZATION IN KEPLARATE-TYPE POLYOXOMETALATES

In this paper, we present direct evidences for two-stage mechanism of crystallization of patchy colloids from replica exchange Monte Carlo simulations. The patchy model colloid mimics the structure and interactions of a certain class of polyoxometalates (POM). We find that individual colloids self-assemble into two-dimensional sheets in hexagonal close-packed structure, and these sheets themselves stack to form crystals. The simulation explains the formation of hollow shelllike objects in POM solution [T. Liu, B. Imber, E. Diemann, G. Liu, K. Cokleski, H. Li, Z. Chen and A. Muller, J. Am. Chem. Soc. 128, 15914 (2006)]. Simulation also predicted the formation of pentagonal caps that are essential for the formation of hollow, closed shells of POMs. Similar twostep crystallization of apoferritin protein was earlier found in experiments [S. T. Yau and P. G. Vekilov, Nature 406, 494 (2000)]. The simulation study suggests nonclassical route to crystallization in patchy colloids.