Eu 2 Li(C 3 )H: A Carbide Hydride Phase Incorporating Eu 2+

High Resolution Image Download MS PowerPoint Slide Reactions between carbon and lithium hydride in a mixed metal europium/lithium flux led to the synthesis of Eu 2 Li(C 3 )H. At room temperature, the compound crystallizes in the tetragonal space group P 4/ mbm (no. 127, Z = 2; Ca 2 Li(C 3 )H type) and undergoes a second-order structural phase transition below ∼250 K to an orthorhombic low-temperature modification (no. 55, Pbam; Z = 4), crystallizing in a new structure type. The phase transition was monitored by using single-crystal X-ray diffraction (SCXRD) and temperature-dependent high-resolution powder diffraction data. Infrared (IR) spectroscopy and gaschromatographic analysis (GC) of the hydrolysis products confirm the existence of a first europium compound with an allylenide anion (C 3 4– ). Magnetic susceptibility measurements and 151 Eu Mössbauer spectroscopy reveal the presence of divalent europium, suggesting a charge-balanced carbide hydride (Eu 2+ ) 2 (Li + )(C 3 4– )(H – ). A transition to a (soft) ferromagnetic ground state is observed below 42 K. In situ high-pressure, high-temperature (HPHT) investigations indicate a surprisingly high stability of Eu 2 Li(C 3 )H and yield a bulk modulus K 0 = 65 GPa. Quantum chemical calculations (DFT + U ) reveal a pseudogap at the Fermi level and allow the classification as a rare-earth metal Zintl phase exhibiting both ionic and covalent bonding contributions.