A HELICAL FACE-SHARING TETRAHEDRON CHAIN WITH IRRATIONAL TWIST, STELLA-QUADRANGULA, AND RELATED MATTERS

Aggregates in which tetrahedra share faces are rare; this paper describes the electronic structure of some one-dimensional chains of this type. The archetype is gracefully winding triple helix with irrational twist, also described by R. Buckminster Fuller as a tetrahelix. We examine some realizations of this structure exemplified by stoichiometries such as BR, PtCO, CuI, and Tal. Optimum electron counts for approaching stability in this structural type are given. A related tetracapped tetrahedral building block, the Stella quadrangula or tetraederstern, is also the subject of calculations. Undeformed, it cannot propagate in space, but a relatively small distortion of all tetrahedra leads to a reasonably common stacking unit. © 1990, American Chemical Society. All rights reserved.