Synthesis and crystal structures of RERhIn (RE=Sm, Tb, Ho, Er, Tm, Yb, Lu)

The intermetallic rare earth metal compounds RERhIn (RE=Sm, Tb, Ho, Er, Tm, Yb and Lu) were synthesized from the elements by arc-melting, by reactions in sealed niobium tubes in a high-frequency furnace, or by induction melting in glassy carbon crucibles. All compounds were investigated by X-ray powder diffraction and the structures have been refined on the basis of single-crystal diffractometer data: ZrNiAl type, P6̄2m, a=750.93(8), c=397.52(4) pm, wR2=0.027, 273 Fo 2 values for SmRhIn, a=748.0(2), c=390.4(1) pm, wR2=0.054, 238 Fo2 values for TbRhIn, a=747.21(6), c=385.72(3) pm, wR2=0.036, 223 Fo2 values for HoRhIn, a=746.5(1), c=384.01(9) pm, wR2=0.040, 337 Fo2 values for ErRhIn, a=747.17(8), c=380.47(6) pm, wR2=0.029, 335 Fo2 values for TmRhIn, with 14 variables per refinement, and TiNiSi type, Pnma, a=692.9(3), b=414.1(2), c=849.0(3) pm, wR2=0.082, 591 Fo2 values for YbRhIn, a=690.3(1), b=413.12(8), c=848.2(2) pm, wR2=0.044, 589 Fo2 values for LuRhIn, with 20 variables per refinement. In both structure types, the rhodium and indium atoms build a three-dimensional [RhIn] network with strong Rh–In and In–In bonding in which the rare earth metal atoms fill distorted hexagonal channels. The switch in crystal structure from TmRhIn to YbRhIn is ascribed to geometrical effects. The crystal chemistry of these intermetallic compounds is briefly discussed.