LaPt 2 Ge 2 und EuPt 2 Ge 2 – Neubestimmung der Kristallstrukturen

LaPt 2 Ge 2 and EuPt 2 Ge 2 – Revision of the Crystal Structures LaPt 2 Ge 2 was rechecked by single crystal X‐ray methods resulting in space group P 2 1 / c (in place of P 2 1 ) and the lattice constants a = 9.953(3), b = 4.439(1), c = 8.879Å, β = 90.62(4)°, and Z = 4. In contrast to previous reports the cell volume had to be doubled. The same is true for EuPt 2 Ge 2 ( a = 9.731(1), b = 4.446(1), c = 8.823(1) Å, β = 91.26(1)°). The crystal structures correspond to a monoclinic variant of the tetragonal CaBe 2 Ge 2 type, whereas the distortion can be described as different rotations of the coordination polyhedra around the La and Eu atoms, respectively. It is most likely that the compounds A Pt 2 Ge 2 with A = Ca, Y, La‐Dy undergo phase transitions at higher temperatures forming then the undistorted CaBe 2 Ge 2 type, space group P 4/ nmm . This was confirmed for SmPt 2 Ge 2 ( a = 4.292(1), c = 9.980(1) Å; Z = 2) and might also be the case for A Pt 2 Ge 2 with A = Ca, Nd, Sm, Eu, and Gd.