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 ASmGeSe4 (A = K, Rb, Cs). Using a constant reactant stoichiometry,
we relate the monoclinic KLaGeSe4 structure type to the orthorhombic CsSmGeS4 structure type. KSmGeSe4 [in
space group P21 with cell parameters a = 6.774(1) Å, b = 6.994(1) Å, c = 8.960(2) Å, β = 108.225(3)°, and V
= 403.2(1) Å3 (Z = 2)], RbSmGeSe4 [in space group P212121 with cell parameters a = 6.7347(8) Å, b = 7.0185(9)
Å, c = 17.723(2) Å, and V = 837.7(2) Å3 (Z = 4)], and CsSmGeSe4 [in space group P212121 with cell parameters
a = 6.707(2) Å, b = 7.067(2) Å, c = 18.334(6) Å, and V = 869.1(5) Å3 (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 NaSmGeSe4 was found
with the cell parameters a = 6.897(2) Å, b = 9.919(2) Å, c = 11.183(2) Å, α = 84.067(4)°, β = 88.105(4)°, γ
= 73.999(4)°, and V = 731.5(3) Å3. In addition to single-crystal diffraction, Raman and diffuse reflectance UV−visible spectroscopic measurements have been used to characterize these compounds.