Cluster self-organization of silicate and germanate systems: Invariant suprapolyhedral cluster precursors and self-assembly of the crystal structures of Li,TR silicates (germanates)

Abstract

The initial stages of formation of suprapolyhedral clusters (containing polyhedra of different types) in an evolving chemical system are considered. The suprapolyhedral clusters of the chain and cyclic types are used for modeling two-dimensional periodic structures. The developed model is used to search for cluster precursors in the structures of Li,TR silicates (germanates) of the known structure types. The complete threedimensional reconstruction of the self-assembly of Li,TR silicates (germanates) is performed using computer methods (with the TOPOS program package) according to the following scheme: cluster precursor → primary chain → microlayer → microframework (supraprecursor) → … framework. Two types of invariant cyclic cluster precursors composed of the TR polyhedra linked by tetrahedra and the TR polyhedra joined by diorthotetrahedra are identified in five and two structures, respectively. It is revealed that the lithium atoms are located at the centers of all clusters. New types of two-dimensional nets with a hierarchical structure formed as a result of the packing of cyclic four-, six-, and eight-node clusters are described.