Crystal structure of SrΛ2TRNbOΛ6 compounds (TR=Sm, Tm)

Crystal structure of Sr2SmNbO6 and Sr2TmNbO6 compounds (automatic diffractometer CAD4, total number of reflections - 1911 and 1030 respectively) was determined. For Sr2SmNbO6 a=5.844, b=5.934, c=8.313 A, β=90.13 deg, V=288.A3, z=2, space group P2 sub(1/n), rho calculated = 5.96 g/cm3; for Sr2TmNbO6 a=5.790, b=5.811, c=8.203 A, V=276.0 A3. z=2, space group Psub(2nn), rho calculated=6.45 g/cm3. The refinement of coord.nates and thermal parameters of structures by the least square method in the anisotropic approximation resulted in R=0.062 and Rsub(ω)=0.073 in the first case and R=0.051 and Rsub(ω)=0.065 in the second case. It is shown that the structures crystallize in the crystal type of distorted cryolite