The structural type and related concepts of crystal chemistry
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TAL CHEMISTRY Dedicated to the memory of G.B. Bokiі on the occasion of his 100th birthday
The Structural Type and Related Concepts of Crystal Chemistry V. S. Urusov Moscow State University, Moscow, 119992 Russia email: [email protected] Received March 19, 2009
Abstract—A detailed historical review is presented and the difficulties arising when defining such a funda mental concept as structural type in crystal chemistry are analyzed. Particular attention is paid to the genetic relationship between different structural types and to the criteria of choosing between them. Many other terms and concepts of modern crystal chemistry defined for completeness. PACS numbers: 61.50.Ah DOI: 10.1134/S106377450905006X
Among the approximately 400 scientific publica tions by G.B. Bokiі [1], the titles of no less than 60 contain words such as systematics, nomenclature, classification, and thesaurus. Many of his reports and speeches, which are fondly remembered by the author of this paper, were devoted to these problems. Bokiі’s contribution to this subject is noted in the preface to this jubilee issue. For this reason I decided to focus again on one of the central concepts of structural crys tal chemistry: structural type (ST), which lies in the basis of systematics but nevertheless remains one of the most uncertain and debated, alongside other con cepts, that is related to it genetically and through mutual transitions.
more numerous artificial (according to Bokiі) or, in other words, functional classifications order informa tion, organize empirical facts, and pave the way for discovering new laws. Therefore, they play an impor tant role in all natural sciences, where empirical knowledge and observations are accumulated with increasing rate and often advance the development of models, hypotheses, and theories. Bokiі was an active founder of the theory of informatics and made a signif icant contribution to the solution of related problems in at least two sciences: mineralogy and structural crystal chemistry. Similar to the fundamental taxon of mineral species (MS) in mineralogy, the ST concept in crystal chemis
The fact that all fundamental scientific concepts are constantly analyzed and revised indicates that the corresponding field of science is actively developing and rising to ever higher levels of cognition. Even the classifications that Bokiі referred to as natural (he assigned, along with the periodical law of chemical elements, 32 symmetry classes, 47 simple forms of finite crystals, and 230 space groups of crystal struc tures to such classifications) are subjected now and then to a deeper reconsideration and elaboration. One example of such expansion and deepening of the knowledge of these classifications is the derivation of 146 physically different simple forms of crystals by Bokiі in 1940, which was immediately included in a wellknown crystallography textbook [2]. Another example was a way to distribute chemical elements over subgroups in the Periodic Table proposed by Bokiі based on a crystallochemical ana
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