Author(s): A.A. Al-Aql, Z.H. Dughaish, A. Al-Jufali, K.M. Al-Sheibani, E.M.A. Hameida and A. Flimban
Article publication date: 1996-04-01
Vol. 14 No. 1 (yearly), pp. 249-260.
129
Keywords
crystal structure, chlorine ions, lattice
Abstract
The crystal structure of the compound Cs3Mg2Cl7 is studied and found to consist of layers of distinct double perovskite type formed parallel to the plane (001) and the following layers are displaced by a/√2 in the direction [110].
The compound is tetragonal of the space group 14/mmm and the lattice parameters are:
a=0.505(1)nm
c=2.630(5)nm
The experimental density, Dm= 3.40 g/cm and the theoretical density Dx= 3.45 g/cm. The number of molecules per unit cell Z=2 and the reliability factor Rw= 5.8%.
The Mg++, Cs+ (1) amd Cs+ (2) lie in different layers perpendicular to c-axis with Z=0 for Cs+(2), Z=0.1899 (6) for Cs+ (1) and Z=0.4021 (8) for Mg++. The Mg++ is surrounded approximately octahedrally by six chlorine ions, while Cs+(1) by nine chlorine ions and Cs+ (2) by twelve chlorine ions.