Metal Flux Growth of Lanthanide Carbide Hydrides Using Anthracene

Reactions of anthracene in Ln/T eutectic mixtures (Ln = La, Yb; T = Ni, Cu) have produced crystals of new complex lanthanide carbide hydride phases. The thermal decomposition of anthracene provides a source of both carbon and hydrogen. LaCH forms in space group with unit cell parameters a = 7.2736(4) Å, b = 3.7218(2) Å, and c = 13.0727(7) Å. Yb₂CH forms in space group P-3m1 with unit cell parameters a = 3.5659(4) Å and c = 5.8000(8) Å, with a structure related to that of Ho₂CF₂. The presence of hydride in interstitial sites is supported by the formation of different compounds in the absence of hydrogen and by comparison to known hydride structures. ¹H nuclear magnetic resonance (NMR) spectra collected on LaCH show two unique hydride resonances, in agreement with the two available interstitial sites. Density of states calculations show that filling the tetrahedral sites in LaCH with hydrogen increases metallic behavior, while adding hydrogen into the tetrahedral sites in Yb₂CH induces the formation of a band gap.