On the solid solutions Eu_1-xPt₂In_x, Gd_1-xPt₂In_x, and Tm_1-xNi ₂In_x

The binary cubic Laves phases EuPt₂, GdPt₂, and TmNi₂ form extended solid solutions Eu_1-xPt ₂In_x, Gd_1-xPt₂In_x, and Tm_1-xNi₂In_x. Samples within these homogeneity ranges have been prepared from the elements by arc-melting on water-cooled copper chills or by induction melting in sealed tantalum tubes and subsequent annealing. The indides were characterized by X-ray powder and single crystal diffraction: MgCu₂ type, Fd3m, a = 770.68(6) pm, wR2 = 0.0251, 67 F² values, 6 variables for Eu_0.94(3)Pt₂In _0.06(3), a = 769.16(6) pm, wR2 = 0.0244, 67 F² values, 6 variables for Eu_0.85(2)Pt₂In_0.15(2), a = 760.12(9) pm, wR2 = 0.0693, 65 F² values, 6 variables for Gd _0.79(5)Pt₂In_0.21(5), and MgCu₄Sn type, F43m, a = 700.27(6) pm, wR2 = 0.0368, BASF = 0.13(2), 175 F² values, 8 variables for TmNi₄In. The platinum and nickel atoms build up three-dimensional networks of corner-sharing Pt_4/2 and Ni _4/2 tetrahedra. These networks leave larger voids of coordination number 16 that are filled with the rare earth (RE) and the indium atoms. While the thulium and indium atoms are ordered in TmNi₄In, one observes mixed RE/In occupancies in Eu_0.94(3)Pt₂In _0.06(3), Eu_0.85(2)Pt₂In_0.15(2), and Gd_0.79(5)Pt₂In_0.21(5).