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Topological relation between the LaIrSi- and the EuNiGe-type structures in ternary phasesMPdSi (M= Ca, Eu, Sr, Ba)

Journal of Solid State Chemistry
Publication Date
DOI: 10.1016/0022-4596(91)90079-w
  • Mathematics


Abstract The LaIrSi-type structures has been established for SrPdSi ( cP12, P2 13, a = 650.0(1) pm, R = 4.40%) by a single crystal investigation and for EuPdSi ( a = 641.9(1) pm) and BaPdSi ( a = 666.2(1) pm) by Guinier powder experiments in Rietveld technique. In the LaIrSi-type structure a three-dimensional net is built up in which each transition metal atom has three Si neighbors (and vice versa). This net is a slightly distorted version of the ideal (10,3)a-net and projects as 4.8 2-net. For CaPdSi ( mP12, P2 1 n , a = 588.2(1), b = 575.3(1), c = 734.7(1) pm , β = 109.63(1)°, R = 2.05%) the EuNiGe-type structure has been derived by a single crystal investigation. Again, each transition metal atom has three Si neighbors (and vice versa), but now layers of distorted 4.8 2-nets are formed. This net is reminiscent of the (10,3)d-net and shows a topological relation to the (10,3)a-net found in the LaIrSi-type structure. The nets differ in the chirality of their constituent screws of three-connected atoms. Due to the denser packing of the EuNiGe-type structure in comparison to the LaIrSi-type structure a high pressure transformation of the second to the first is favored.

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