Potential Zeolites Related to Faujasite: Structures and Energetics

We describe five new zeolitic framework types, fav, faw, fax, fay, and sod-t, that are structurally related to faujasite. They are derived from isomorphic expansions of the tetrahedral nets associated with selected Frank-Kasper phases. Each tetrahedral vertex of the net is replaced by a sodalite cage (S) and each edge by a hexagonal prism (P), in effect replacing each vertex with an SP4 tetrahedron. Faujasite itself, framework type FAU, is an SP4 expansion of the diamond net. In the Frank-Kasper phases, the periodic incorporation of icosahedra, which can be subdivided into 20 almost-regular tetrahedral volumes, tends to minimize distortion of the associated tetrahedral SP4 framework, ensuring low framework energies. The computed framework energy of silicate fav compares most favorably with that for FAU and EMT, presenting an appealing zeolite synthesis target.