Framework structures derived from a novel type of trigonal secondary building unit with on-axis T atoms: the tridymite group

Abstract

An infinite series of secondary building units generated around a trigonal axis, with the top and/or bottom T atom coinciding with the symmetry axis allows the systematic enumeration of a novel class of (4; 2)-connected 3D framework structures. Known members of this group are the framework topologies of tridymite, cristobalite, MAPSO-46 (AFS), CoAPO-50 (AFY) and beryllophosphate-H (BPH). Adjacent T atoms on a trigonal axis with a T-O-T bond angle of 180 o (T2 unit) present in all structures confer some specific properties on this class of compounds. AbstractForty-two hypothetical 3 D nets are derived by applying four types of transformations (or combinations thereof) to the previously described tridymite group of structures. Two novel transformations are proposed, one preserving the (hexagonal or orthorhombic) symmetry and another converting the hexagonal symmetry into orthorhombic.Correspondingly, groups of hypothetical 3D framework structures are derived. The properties of frameworks belonging to these groups are compared and discussed.

How Many Networks Can Be Made from Four-Coordinate Atoms?

“…However, they admit certain shortcomings in their procedure and state that their list is not complete. Unfortunately, Dress et al [8] do not comment on this; they also do not cite the numerous earlier papers dealing with the systematic classification and numbering of structural possibilities of zeolites (and other networks), for example by Smith [11] or by Bosmans and Andries [12] (see refs. [10] and [12] for many other citations).…”

Wie viele kristalline Netzwerke aus vierfach koordinierten Atomen gibt es?

“…ten, die sich mit der systematischen Klassifizierung und Abzählung der Strukturmöglichkeiten von Zeolithen (und anderen Netzwerken) befassen, z. B. von Smith et al [11] oder von Bosmans und Andries [12] (zahlreiche weitere Zitate siehe unter Lit. [10] und [12] [13] in die für uns besser zugängliche Kristallographen-Sprache übersetzt und die Anwendung auch gleich bei Schichtsilicaten, den Stapelvarianten von dichtesten Kugelpackungen und den Substitutionsderivaten des Wurtzit-Typs vorgeführt; [14] weitere Ausführungen dazu siehe auch unter Lit.…”