Stabilizing the LaCoAl4 structure through indium-magnesium substitution in CeRhIn4-xMgx (x=0.79 and 0.84) - An indide with magnesium centered indium cubes

摘要

The intermetallic compounds CeRhIn4-xMg, (X = 0.79 and 0.84) were prepared from the elements in sealed tantalum ampoules in a high-frequency furnace. The samples were investigated by X-ray powder and single crystal diffraction: LaCoAl4 type, Pmma, a = 829.5(2), b = 433.56(9), c = 740.2(2) pm, wR2 = 0.0458, 651 F-2 values, 25 variables for CeRhIn3.21Mg0.79 and a = 831.44(10), b = 433.49(10), c = 741.04(10) pm, wR2 = 0.0543, 915 F-2 values, 25 variables for CeRhIn3.16Mg0.84. The indium atoms build up two-dimensional networks perpendicular to the b axis in an AA stacking sequence leaving slightly distorted trigonal, square and pentagonal prismatic voids for the rhodium, magnesium, and cerium atoms. Both square prismatic voids show small magnesium/indium mixing. The shortest interatomic distances occur for the Rh-Mg contacts (257 pm). Together, the rhodium, indium, and magnesium atoms build up three-dimensional [Rhln(4-x)Mg(x)] networks in which the cerium atoms fill distorted pentagonal channels.