Enumeration of Subperiodic Zeolitic Tetrahedral Frameworks. III. Layers, Rods, Tubes, and Clusters

We describe a new database of 4-coordinated hypothetical
“subperiodic”
zeolitic frameworks, comprising 0-periodic (clusters), 1-periodic
(rods and tubes), and 2-periodic (layers) structures. The structures
are found by a combinatorial search over 4-coordinated directed graphs,
given the space group and the number of unique tetrahedral vertices,
as in our earlier database. However, the filters are now reversed
to reject the 3-periodic zeolites. Being fully 4-coordinated, these
subperiodic structures require no hydroxyl terminations at their free
surfaces when realized as SiO2 silicates. The layers closely
resemble thin zeolites and are particularly interesting candidates
for synthesis. The layer structures offer a rich library of structural
possibilities for low-energy termination of the free surfaces of the
known zeolites while maintaining full tetrahedral coordination. We
present two examples of possible (001)-surface reconstructions for
the LTL framework.