Symmetry and topology code of cluster self-assembly of icosahedral framework structures of boron and borides

Abstract

The topological types of suprapolyhedral clusters composed of i-B12 icosahedra have been modeled. The models of icosahedral supraclusters have been used in analysis of the crystal structures of boron and borides (the TOPOS program package). To identify nanocluster precursors in crystal structures, there have been used special algorithms for partitioning structural graphs into disjoint substructures and constructing a basis 3D network of the structure as a graph with the nodes corresponding to the positions of the centroids of the cluster precursors. The cluster self-assembly have been modeled for 25 types of icosahedral framework structures of boron—B12-hR 12, (B12)2(B2)2-oP 28, (B12)4B2-P50, B196-tP 196, and B333-hR 333; binary borides—(B12)O2-hR 14, (B12)P2-hR 14, and (B12)(CBC)-hR 15; templated metal borides—Na2(B12)2B6-oI 64, Mg2(B12)B2-oI 68, Tb(B12)(B4)-mI 60, Al4(B12)4B8-oC 88, (B12)4(Si4)4-oI 64, (B12)4B2Be4-tP 58, Ti2(B12)4B2-tP 52, Sc12B180-tP 192, Cu4Sc12B180-tP 192, Si1.5Sc9B178-tP 216, Mg28B360-oP 388, Al28B352-oP 384, Si28B352-oP 306, Y24(B156)8(B39)8-cF1944, Sc10B315-hR339, and Li24B315-hR336. The symmetry and topology code of the crystal structure self-assembly from nanocluster precursors in the form of primary chain → microlayer → microframework has been completely restored. Frequency analysis of various topological and symmetry pathways for the formation and evolution of cluster precursors makes it possible to elucidate crystal-formation trends in inorganic systems at the microscopic level.