COHERENCE ASSEMBLY PHENOMENON IN THE TYPICAL STRUCTURES OF HETEROPOLYNIOBATES
S. V. Borisov, S. A. Magarill, N. V. Pervukhina
Nikolaev Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: crystallographic analysis, coherence assembly, cation framework, building blocks, polyoxoniobates, menezesite, aspedamite
Abstract
Crystallographic analysis has provided evidence for single cation frameworks formed from preordered cation positions in the individual building blocks (modules) constituting the basis of structures. We propose to call this phenomenon coherence assembly . According to the mechanical wave concept of the crystalline state, coherence assembly dictates the rules of mutual packing of “rigid” structural fragments. This study investigates the typical structures of heteropolyniobates: Na12[Ti2O2][SiNb12O40]×4H2O (I), menezesite Ba2MgZr4[BaNb12O42]×12H2O (II), and the menezesite-isostructural aspedamite □12(Fe3+,Fe 2+)3Nb4×[Th(Nb,Fe3+)12O42]×(H2O,OH)12 (III).
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