Neue Germanide mit geordneter Ce₃Pt₄Ge₆‐Struktur – Die Verbindungen <i>Ln</i>₃Pt₄Ge₆ (<i>Ln</i>: Pr–Dy)

Abstract

Abstract New Germanides with an Ordered Variant of the Ce 3 Pt 4 Ge 6 Type of Structure – The Compounds Ln 3 Pt 4 Ge 6 ( Ln : Pr–Dy) Six new germanides Ln 3 Pt 4 Ge 6 with Ln = Pr–Dy were synthesized by heating mixtures of the elements at 900 °C, annealing the inhomogeneous powders at 1050‐1100 °C for six days and then cooling down from 700 °C in the course of two months. The crystal structures of Pr 3 Pt 4 Ge 6 ( a = 26.131(5), b = 4.399(1), c = 8.820(2) Å), Sm 3 Pt 4 Ge 6 ( a = 25.974(3), b = 4.356(1), c = 8.748(1) Å), and Dy 3 Pt 4 Ge 6 ( a = 26.079(5), b = 4.311(1), c = 8.729(2) Å) were determined by single crystal X‐ray methods. The compounds are isotypic ( Pnma , Z = 4) and crystallize with an ordered variant of the Ce 3 Pt 4 Ge 6 type of structure ( Cmcm , Z = 2) consisting of CaBe 2 Ge 2 ‐ and YIrGe 2 ‐analogous units. The platinum atoms are located in distorted square pyramids of germanium atoms and build up with them a three‐dimensional network. The coordination polyhedra of the platinum and germanium atoms around the rare‐earth metal atoms are pentagonal and hexagonal prisms. These are completed by some additional atoms resulting in coordination numbers of 14 and 15 respectively. The other germanides were investigated by powder methods resulting in the following lattice constants: a = 26.067(6), b = 4.388(1), c = 8.800(2) Å for Ln = Nd; a = 25.955(7), b = 4.337(1), c = 8.728(2) Å for Ln = Gd; a = 25.944(5), b = 4.322(1), c = 8.698(2) Å for Ln = Tb. The atomic arrangement of Ln 3 Pt 4 Ge 6 is compared with the well‐known monoclinic structure of Y 3 Pt 4 Ge 6 .