Magnesium‐Tin Substitution in NiMg2

Abstract

AbstractThe binary intermetallic compound NiMg2 (own structure type) forms a pronounced solid solution NiMg2−xSnx. The structure of NiMg1.85(1)Sn0.15(1) was refined on the basis of single crystal X‐ray data: P6422, a = 520.16(7), c = 1326.9(1) pm, wR2 = 0.0693, 464 F2 values, and 20 variables. With increasing magnesium/tin substitution, the structure type changes. Crystals with x = 0.22 and 0.40 adopt the orthorhombic CuMg2 type: Fddd, a = 911.0(2), b = 514.6(1), c = 1777.0(4) pm, wR2 = 0.0427, 394 F2 values for NiMg1.78(1)Sn0.22(1), and a = 909.4(1), b = 512.9(1), c = 1775.6(1) pm, wR2 = 0.0445, 307 F2 values for NiMg1.60(1)Sn0.40(1) with 19 variables per refinement. The nickel atoms build up almost linear chains with Ni–Ni distances between 260 and 263 pm in both modifications where each nickel atom has coordination number 10 with two nickel and eight Mg/Sn neighbors. Both magnesium sites in the NiMg2 and CuMg2 type structures show Mg/Sn mixing. The Ni polyhedra are condensed leading to dense layers which show a different stacking sequence in both structure types. The crystal chemical peculiarities of these intermetallics are briefly discussed.