Crystallochemical model and prediction for zeolite-type structures

Abstract

A model for zeolite-type structures, which considers anion coordinations, is established on the basis of crystallochemical rules. Careful observation of 42 structures of zeolite-type minerals verifies the model. The numerical analysis which follows takes account of a scheme for charge transfer in the structures and allows structural chemical conditions to be established for these structures using simple numerical expressions. Accordingly, the atom coordinations in structures can be calculated directly from the chemical composition, which means that prediction of the atom coordinations in zeolite-type structures is now possible. In this paper, this prediction is carried out for some 30 known zeolite-type structures whose cavities, beside water oxygens or other anions, are filled with one type of cavity cation. The results are compared with the observations. It is shown that even the coordination of the cavity cation can be predicted within a fairly good approximation. For zeolite types with an interrupted framework, breaking of the tetrahedral framework is shown to be a consequence of charge equilibrium between the tetrahedral framework and the anions in cavities. A global structural analysis of zeolite-type structures has attracted greater interest as more and more synthetic or natural zeolite-type structures have become known. Refinements of several of these structures are, however, often incomplete because of disorder. At this stage of knowledge, the model and following numerical formulations may find several applications: i.e. in evaluating structures from chemical formulae, for the determination of possible order in disordered structures, for the synthesis of new materials, and for classification. This is a first attempt to define whole structures from chemical compositions using numerical expressions.

Ab initio prediction of low-temperature phase diagrams in the Al–Ga–In–As system, MAs–M′As (M, M′ = Al, Ga or In) and AlAs–GaAs–InAs, via the global study of energy landscapes

“…17 For more details regarding energy landscapes and chemical systems, we refer to the literature. [13][14][15]18 Based more or less explicitly on these general concepts, there have been many efforts to study the energy landscape of solids and extract information relevant for, especially, structure prediction, [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] structure determination, [6][7][8][9][10]37 and phase diagram computation; for reviews see e.g.refs. 1-3, 13, 15, 18, and 60-63.…”

Hydrous Phases and Hydrogen Bonding at High Pressure

“…As Hawthorne (1992) points out, one of the principal consequences of the presence of OH -in crustal oxide and oxy-salt minerals is to limit the dimensionality of the structures that host them. Along with those minerals quoted by (Hawthorne 1992(Hawthorne , 1994, interrupted microporous frameworks are also excellent examples of this phenomenon (Parise 1984, Engel 1991, Bedard et al 1993, Tazzoli et al 1995. The terminal OH -group is common in clays and the hydroxides related to the CdI 2 structure are particularly useful low-dimensional materials for the study of hydrogen bonding.…”