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The intermetallic compound LiMnBi was synthesized by the two-step solid-state reaction from the elements. A synthesis temperature of 850 K was selected based on in situ high-temperature powder X-ray diffraction data. LiMnBi crystalizes in the layered-like PbClF structure type (a = 4.3131(7) Å, c = 7.096(1) Å at 100 K, P4/nmm space group, Z = 2). The LiMnBi structure is built of alternating [MnBi] and Li layers, as determined from single-crystal X-ray diffraction data. Magnetic property measurements and solid-state 7Li nuclear magnetic resonance data collected for polycrystalline LiMnBi samples indicate the long-range antiferromagnetic ordering of the Mn sublattice at ∼340 K, with no superconductivity detected down to 5 K. LiMnBi is air- and water-sensitive. Under aerobic conditions, Li can be extracted from the LiMnBi structure to form Li2O/LiOH and MnBi (NiAs structure type, P63/mmc). The obtained MnBi polymorph was previously reported to be one of the strongest rare-earth-free ferromagnets, yet its bulk synthesis in powder form is cumbersome. The proposed magneto-structural transformation from ternary LiMnBi to ferromagnetic MnBi involves condensation of the MnBi4 tetrahedra upon Li deintercalation and is exclusive to LiMnBi. In contrast, ferromagnetic MnBi cannot be obtained from either isostructural NaMnBi and KMnBi or from the structurally related CaMn2Bi2. Such a distinctive transformation in the case of LiMnBi is presumed to be due to its fitting reactivity to yield MnBi and a favorable interlayer distance between [MnBi] layers, while the interlayer distance in NaMnBi and KMnBi structural analogues is unfavorably long. The studies of delithiation from layered-like LiMnBi under different chemical environments indicate that the yield of MnBi depends on the type of solvent used and the kinetics of the reaction. A slow rate and mild reaction media lead to a high fraction of the MnBi product. The saturation magnetization of the “as-prepared” MnBi is ∼50% of the expected value of 81.3 emu/g. Overall, this study adds a missing member to the family of ternary pnictides and illustrates how soft-chemistry methods can be used to obtain “difficult-to-synthesize” compounds. 

With the motivation of searching for new superconductors in the Mg–B system, we performed ab initio evolutionary searches for all the stable compounds in this binary system in the pressure range of 0–200 GPa. We found previously unknown, yet thermodynamically stable, compositions MgB 3 and Mg 3 B 10 . Experimentally known MgB 2 is stable in the entire pressure range 0–200 GPa, while MgB 7 and MgB 12 are stable at pressures below 90 GPa and 35 GPa, respectively. We predict a reentrant behavior for MgB 4 , which becomes unstable against decomposition into MgB 2 and MgB 7 at 4 GPa and then becomes stable above 61 GPa. We find ubiquity of phases with boron sandwich structures analogous to the AlB 2 -type structure. However, with the exception of MgB 2 , all other magnesium borides have low electron–phonon coupling constants λ of 0.32–0.39 and are predicted to have T c below 3 K. 

We explored the B–C–O system at pressures in the range 0–50 GPa by ab initio variable-composition evolutionary simulations in the hope of discovering new stable superhard materials. A new tetragonal thermodynamically stable phase B 4 CO 4 , space group I 4̄, and two low-enthalpy metastable compounds (B 6 C 2 O 5 , B 2 CO 2 ) have been discovered. Computed phonons and elastic constants show that these structures are dynamically and mechanically stable both at high pressure and zero pressure. B 4 CO 4 is thermodynamically stable at pressures above 23 GPa, but should remain metastable under ambient conditions. Its computed hardness is about 38–41 GPa, which suggests that B 4 CO 4 is potentially superhard.