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Crystal chemistry of MX · MgX 2 · 6H 2 O type compounds

1988; Wiley; Volume: 563; Issue: 1 Linguagem: Inglês

10.1002/zaac.19885630122

1521-3749

H.‐H. Emons, P. Brand, T. Pohl, K. Köhnke,

Nuclear materials and radiation effects

Abstract The following MX · MgX 2 · 6H 2 O compounds (double salt hexahydrates) were synthesized by variation of the M + and X − ions: CsCl · MgCl 2 · 6 H 2 O, Li(H 2 O)Cl · MgCl 2 · 6H 2 O, NH 4 Br · MgBr 2 · 6 H 2 O, RbBr · MgBr 2 · 6 H 2 O, CsBr. MgBr 2 · 6 H 2 O, KI · MgI 2 · 6 H 2 O, NH 4 I. Mgl 2 · 6 H 2 O and RbI · MgI 2 · 6H 2 O. By X‐ray analysis of powder samples the lattice parameters and the space group were determined. On the basis of the results thus obtained, an identification with structural types was carried out. In accordance with the findings, the structure is made up of (M + )X 6 − octahedra which are linked into perovskite type units by sharing vertices. Their interstices are occupied by the Mg(H 2 O) 6 2+ octahedra. A “tolerance factor” t which has been calculated on the basis of the proportion of radii and which attains values between 1.045 and 1.061 is a criterion for the upper limit of the area of existence of this structure. Carnallite has a higher to value and, therefore, a different structure.