Synthesis, Crystal Structure, and Compressibilities of Mn_3-x Ir₅ B_2+x (0≤x≤0.5) and Mn₂ IrB₂

The new ternary transition metal borides Mn_3-x Ir₅ B_2+x (0≤x≤0.5) and Mn₂ IrB₂ were synthesized from the elements under high temperature and high-pressure/high-temperature conditions. Both phases can be synthesized as powder samples in a radio-frequency furnace in argon atmosphere. High-pressure/high-temperature conditions were used to grow single-crystals. The phases represent the first ternary compounds within the system Mn-Ir-B. Mn_3-x Ir₅ B_2+x (0≤x≤0.5) crystallizes in the Ti₃ Co₅ B₂ structure type (P4/mbm; no. 127) with parameters a=9.332(1), c=2.896(2) Å, and Z=2. Mn₂ IrB₂ crystallizes in the β-Cr₂ IrB₂ crystal structure type (Cmcm; no. 63) with parameters a=3.135(3), b=9.859(5), c=13.220(3) Å, and Z=8. The compositions of both compounds were confirmed by EDX measurements and the compressibility was determined experimentally for Mn_3-x Ir₅ B_2+x and by DFT calculations for Mn₂ IrB₂ .