Simulation of self-organization processes in crystal-forming systems: Supramolecular cyclic R6 cluster precursors and self-assembly of TeO2-TEL (Tellurite) and TeO2-PAR (Paratellurite) structures

Abstract

The supramolecular chemistry of oxides of sp elements (SO2, SeO2, and TeO2) is considered. The self-assembly of TeO2-TEL (Tellurite) and TeO2-PAR (Paratellurite) crystal structures is simulated. Methods of combinatorial and topological analysis (TOPOS program package) are applied which are based on constructing a basis 3D network of the structure in the form of a graph, the sites of which correspond to the positions of centroids of TeO2 molecules and the edges characterize bonds between them. The topological type of the basis 2D network in the TeO2-TEL structure corresponds to graphite (C-GRA), while in the TeO2-PAR structure the basis network corresponds to the 3D diamond network (C-DIA). A nanocluster precursor of cyclic type (R6) composed of six covalently bound TeO2 molecules (chair conformation) is established for both structures. The desymmetrization of the cyclic structure of the R6 cluster in TeO2-PAR is related to the formation of Te-Te bonds with lengths of 3.824 and 4.062 A. The symmetry and topology code of the processes of self-assembly of 3D structures from nanocluster precursors is completely reconstructed into the form “primary chain → microlayer → microframework.” In both structures R6 clusters form 2D packings with a coordination number of 6. The cluster self-assembly model explains the specific features of the morphogenesis of TeO2-TEL and TeO2-PAR (phases with low and high crystallization temperatures, respectively): platelike shape, perfect cleavage in the (110) plane, and preferred growth in the primar-chain direction [100] in the former case and growth in the direction of the primary [001] axis with the preferred formation of tetragonal prism faces (110) in the latter case.