Structure of uranium-containing elpasolites M2NaUH6

The compounds M2NaUH6, where M = K, Rb, and Cs and H = Cl and Br, were obtained by melting binary components. The compound Rb2NaUBr6 decomposes into Rb2UBr5 and NaBr. The structure was studied by the polycrystal method: K2NaUCl6 has a hexagonal structure of the α-K2LiAlF6 type, Rb2NaUCl6 is orthorhombic, and Cs2NaUCl6 type is F-cubic. K2NaUBr6 has a tetragonal structure of the Rb2NaTmCl6 type and Cs2NaUBr6 is P-cubic. The regularities in the elpasolite structure are discussed in the light of the method of genetic structure types