Abstract
AbstractThe new magnesium based intermetallic compounds Nd4Co2Mg3 and Sm4Co2Mg3 were synthesized by induction melting of the elements in sealed tantalum tubes in a water‐cooled sample chamber. The compounds were studied by X‐ray powder and single crystal diffractometer data: P2/m, a = 765.42(14), b = 380.53(5), c = 832.47(16) pm, β = 109.79(1)°, wR2 = 0.0489, 1026 F2 values for Nd4Co2Mg3, a = 760.12(15), b = 377.11(6), c = 826.84(16) pm, β = 109.68(1)°, wR2 = 0.0518, 731 F2 values for Sm4Co2Mg3 with 30 variable parameters for each refinement. These ternary magnesium compounds crystallize with a new structure type. They are simple 1:3 intergrowth variants of distorted AlB2 and CsCl related slabs of compositions RECo2 and REMg. The Co–Co distance within the AlB2 related slab is 237 pm in Nd4Co2Mg3 and 235 pm in Sm4Co2Mg3. The crystal chemistry of this new structure type is discussed in line with the related structures of Mn2AlB2 and Mo2FeB2 which are 1:1 intergrowth variants of the two slabs.
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