LiCa₃As₂H and Ca₁₄As₆X₇ (X = C, H, N): Two New Arsenide Hydride Phases Grown from Ca/Li Metal Flux

The reaction of arsenic with sources of light elements in a Ca/Li melt leads to the formation of two new arsenide hydride phases. The predominant phase Ca14As6X7 (X = C4–, N3–, H–) exhibits a new tetragonal structure type in the space group P4/mbm (a = 15.749(1) Å, c = 9.1062(9) Å, Z = 4, R1 = 0.0150). The minor phase LiCa3As2H also has a new structure type in the orthorhombic space group Pnma (a = 11.4064(7) Å, b = 4.2702(3) Å, c = 11.8762(8)­Å, Z = 4, R1 = 0.0135). Both phases feature hydride and arsenide anions separated by calcium cations. The red color of these compounds indicates they should be charge-balanced. DOS calculations on LiCa3As2H confirm a band gap of 1.4 eV; UV–vis spectroscopy on Ca14As6X7 shows a band gap of 1.6 eV. Single-crystal neutron diffraction studies were necessary to determine the mixed occupancy of carbon, nitrogen, and hydrogen anions on the six light-element sites in Ca14As6X7; these data indicated an overall stoichiometry of Ca14As6C0.445N1.135H4.915.