A COMPUTATIONAL STUDY OF THE ROLE OF F- IONS IN THE OCTADECASIL STRUCTURE

We report a study of the structures and energetics of F- ions in the o ctadecasil structure. Our calculations find high stability for fluorid e ions within the double 4-ring (D4R) of this structure; the structure is, however, stable in the absence of these species. We propose that fluoride ions are incorporated during the synthesis of the material an d that the high activation energy for their migration out of the D4R r esults in their retention in the structure after calcination. (C) Else vier Science Inc. 1997