Molten flux synthesis of an analogous series of layered alkali samarium selenogermanate compounds.

In this work, we used the molten chalcogenide flux synthetic method to form an analogous series of alkali samarium selenogermanates, with the general formula ASmGeSe(4) (A = K, Rb, Cs). Using a constant reactant stoichiometry, we relate the monoclinic KLaGeSe(4) structure type to the orthorhombic CsSmGeS(4) structure type. KSmGeSe(4) [in space group P2(1) with cell parameters a = 6.774(1) A, b = 6.994(1) A, c = 8.960(2) A, beta = 108.225(3) degrees, and V = 403.2(1) A(3) (Z = 2)], RbSmGeSe(4) [in space group P2(1)2(1)2(1) with cell parameters a = 6.7347(8) A, b = 7.0185(9) A, c = 17.723(2) A, and V = 837.7(2) A(3) (Z = 4)], and CsSmGeSe(4) [in space group P2(1)2(1)2(1) with cell parameters a = 6.707(2) A, b = 7.067(2) A, c = 18.334(6) A, and V = 869.1(5) A(3) (Z = 4)] were formed under identical synthetic conditions by changing the identity of the alkali ion from K to Rb or Cs, respectively. Additionally, with the substitution of sodium into the reaction, a triclinic structure with the approximate formula NaSmGeSe(4) was found with the cell parameters a = 6.897(2) A, b = 9.919(2) A, c = 11.183(2) A, alpha = 84.067(4) degrees, beta = 88.105(4) degrees, gamma = 73.999(4) degrees, and V = 731.5(3) A(3). In addition to single-crystal diffraction, Raman and diffuse reflectance UV-visible spectroscopic measurements have been used to characterize these compounds.