SELF-ASSEMBLY DRIVEN CRYSTALLIZATION IN KEPLARATE-TYPE POLYOXOMETALATES

Abstract

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 shell-like 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 two-step crystallization of apoferritin protein was earlier found in experiments [S. T. Yau and P. G. Vekilov, Nature406, 494 (2000)]. The simulation study suggests nonclassical route to crystallization in patchy colloids.