Principle of modular crystal structure
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TAL CHEMISTRY
Principle of Modular Crystal Structure V. V. Ivanov and V. M. Talanov South Russian State Technical University, Novocherkassk, 346400 Russia email: [email protected] Received November 19, 2008
Abstract—The principle of modular crystal structure has been formulated and the possibility of choosing a module of a specified structure type for its subsequent modular design is discussed. The modular character istics of some structure types based on cubic close packing (fundamental and basic modules and the module that can be used to obtain a certain variety of modular structures related to the initial parent type) are described. Possible ways to obtain such a module and the algorithm for choosing it are considered. A com parative analysis of the theoretically derived module with the modules of experimentally determined modular structures is performed by the example of spinelloids (materials with spinellike structure). DOI: 10.1134/S1063774510030028
INTRODUCTION
THEORETICAL ANALYSIS
The problem of predicting new crystalline materi als with a specified level of manifestation of the struc turesensitive properties that are necessary for practi cal application can be solved, in particular, by the combinatorial modular design of crystals. One can choose a module in each structure type, i.e., a com pact structural unit of material with a certain crystal lochemical topology and composition, corresponding to one formula unit [1]. A combinatorial enumeration of possible (from the point of view of structural and energy crystal chemistry) ways to match these modules in 3D space without changing their crystallochemical topology, as well as an enumeration of possible ways to aggregate these modules into modular blocks with their subsequent arrangement into layers and the packing of these block layers, leads to the formation of a set of new modifications of the initial structure type [2–9]. The efficiency of such combinatorial modular design depends strongly on the topological character istics of the module chosen.
Modular Characteristics of Structure Type
Note that the modules for the modular design of any structure type can be chosen based on a compara tive analysis of this structure type and the correspond ing modular structures that are experimentally deter mined and described in the literature. It is difficult to choose a priori such a module for a specified structure type in the absence of known corresponding modular structures. The purpose of this study is to justify and develop a possible version of the algorithm of choosing modules for the combinatorial modular design of crystal struc tures and approve the algorithm proposed by the example of spinelloids (crystals containing fragments with spinel structure).
There are two ways to search for the initial module for modular design: empirical and theoretical. The empirical approach suggests a comparative analysis of the known crystal structures with the aim of detecting the structural invariants existing in them, which can be used to model new pr
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