Antimony clusters in channels of porous silica ZSM-11

The structure and arrangement of the nanosized antimony clusters synthesized in channels of ZSM-11 porous silica crystals are studied using maximum entropy (MEM) and Rietveld methods. Intercalated antimony atoms are not randomly located in zeolite channels; rather, they form distorted cubic clusters Sb8, with shapes coinciding with that of a fragment of crystalline antimony. The distances between the nearest-neighbor antimony atoms in a cluster are 2.86(6) and 2.88(4) A. The maximum cluster size (4.92 A) matches the minimum free channel diameter of zeolite ZSM-11. The minimum Sb-O distance is 2.68(6) A.