Using the TOPOS program package, 26-atom nanoclusters of the γ-brass (Cu5Zn8) type (0@4@22 or 0@8@18) were found in 5918 crystal structures of cubic intermetallics. The nanocluster models were built for all the intermetallics using a recently developed algorithm implemented into TOPOS. The relations of the structures based on the 0@4@22 core are explored as a result of migration of atoms between different shells of the nanoclusters. It is shown that the 0@4@22 nanoclusters frequently occur as building units of intermetallics of different composition and structure type. Regularities in chemical composition of 702 γ-brass-type nanoclusters were found within both the nanoclusters approach (multishell structure) and the nested-polyhedra model. A database containing all topological types of γ-brass nanoclusters is created with which one can search for the corresponding atomic configuration in any intermetallics.
In this study, we carried out a topological and geometrical analysis of more than 27 000 intermetallics. More than 2000 topologically different nanoclusters were determined and stored in an electronic database as the Topological Types of Nanoclusters (TTN) collection. Besides the topology of the nanoclusters, the TTN collection contains the information on their occurrence as well as on motifs of their assembly in intermetallics; it is included to the set of the ToposPro topological collections. With the TTN collection we analyzed the topology of local binding and overall topological motifs in the 1528 intermetallics assembled with icosahedron-based building units. Taking the TTN collection as a starting point, we present the concept of a knowledge database and an expert system that can be used to process a huge set of data to find general regularities in the crystal structures of intermetallics and to predict some of their features.
The TOPOS software package has been used to form a database of intermetallic compounds con taining pentagondodecahedral d clusters (528 crystal structures of intermetallic compounds, 111 topological types, and 47 space symmetry groups). On the whole, 606 atomic d configurations have been selected which are described by 14 point symmetry groups. Examples of nanoclusters are presented which are precursors of the crystal structures of intermetallic compounds with the outer shell in the form of deltahedra D, which are formed above dodecahedra. These nanoclusters are identified in the automatic mode of structural data pro cessing: 50 are the numbers of atoms in the shell. Similar delta hedra were found previously in icosahedral nanoclusters (precursors of intermetallic compounds). Structures with the dodecahedral nanocluster precursors containing D42 and D50 deltahedra are approximants of MCd 5.7 (M = Yb or Ca) quasicrystals and belong to the family of MCd 6 (M = Ce,
The compound Au10Mo4Zn89 has been synthesized, and its structure has been analyzed by single-crystal X-ray diffraction. The compound crystallizes in cubic space group F43m (No. 216) with a unit cell that contains 412 atoms. The structure is largely tetrahedrally closely packed, but an octahedral arrangement of atoms is incompatible with tetrahedral close packing. The structure of the ordered Au10Mo4Zn89 compound has been described by using the algorithm of automatic geometric and topological analysis that is implemented in TOPOS as the "Nanoclustering" procedure.
A Fully Ordered Complex Intermetallic Compound Analyzed by TOPOS. -The title compound is synthesized from the elements (silica ampule, 1273 K for 2 h followed by annealing at 703 K for 5 d) and characterized by single crystal XRD, EDX, and TB-LMTO-ASA calculations. Au10Mo4Zn89 crystallizes in the cubic space group F43m with Z = 4. The structure is an ordered superstructure of a γ-brass-related structure and is described by using the algorithm of automatic geometric and topological analysis that is implemented in TOPOS as the "nanoclustering" procedure. -(JANA*, P. P.; PANKOVA, A. A.; LIDIN, S.; Inorg. Chem. 52 (2013) 19, 11110-11117, http://dx.doi.org/10.1021/ic4013312 ; CAS Chem. Cent., Lund Univ., S-221 00 Lund, Swed.; Eng.) -W. Pewestorf 50-006
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