The crystal structure of a low-silica dehydrated NaX zeolite

The crystal structure of a low-silica and fully dehydrated NaX zeolite, the synthetic analogue of natural faujasite, with approximate chemical composi tion Na93Al93Si99O384 (Si/Al = 1.06) as determined by microprobe and NMR an alysis, has been determined using single-crystal Cu(K alpha) X-ray diffract ion (a = 25.104(3) Angstrom). X-ray data reduction clearly shows that this crystal has Fd (3) over bar symmetry, as confirmed by the large difference between the Si-O and Al-O distances which indicates a substantial ordering of the Si and Al atoms in tetrahedral sites. All Na+ cations have been loca ted, with refined occupancies of 97 % (site I'), 93 % (site II), 16% (site III'a) and 18% (site III'b); these sites are also those found in a fully de hydrated T1X zeolite.