The Heusler phases LiRh2Si and LiRh2Ge: Synthesis, structure and properties

The isostructural Heusler phases LiRh₂Si and LiRh₂Ge have been synthesized from the elements and an excess of lithium at 1000 °C. Both materials adopt the CuMn₂Al crystal structure, space group Fm−3m (No. 225) with the room temperature lattice parameter a=5.747(1) Å Vol=189.866(1) Å³] and a=5.847(1) Å Vol=199.88(6) Å³] for LiRh₂Si and LiRh₂Ge, respectively. X-ray analyses suggest mixed site occupancy of the form Li_1−xRh₂Si_1+x (x<0.4), but not for LiRh₂Ge. Both materials are diamagnetic, χ_mol(LiRh₂Si)=−6×10⁻⁵ cm³(mole)⁻¹ and χ_mol(LiRh₂Ge)=−10×10⁻⁵ cm³(mole)⁻¹ and metallic with room temperature resistivities of approximately 19 and 32 μΩ cm, respectively. These properties are consistent with the calculated electronic structure.