A refinement of the cation positions in synthetic zeolite type A

The structure of anhydrous synthetic sodium zeolite type A has been refined by the method of least squares. The refined structure has essentially the same Si, A1 and O positions, as given by Reed & Breck (1956), but the 8 Nai ions near the six-membered oxygen rings randomly occupy 24 fold positions of the space group and the 4 Nail ions near the eight-membered oxygen rings randomly occupy another set of 24 fold positions. For the refined structure R =0-16 versus 0-21 for the former model. That the cation positions were in error in the former model was suggested by the calculation of a eoulombic potential map for the structure with the omission of cations.