Crystal structure of the layered arsenide RbCuAs.

The crystal structure of a new arsenide, RbCuAs (trirubidium tricopper diarsenide), has been established from single-crystal X-ray diffraction data. This compound crystallizes in the KCuP type, with layers of interlinked CuAs units. The partitioning of the available valence electrons yields the charge-balanced composition (Rb)(Cu)(As), placing this phase in a broad field of transition-metal-containing Zintl phases. First-principles calculations confirm a semiconducting ground state, in accordance with electron-counting considerations. Chemical bonding analysis reveals strong covalent Cu-As bonds and ionic Rb...As interactions. In addition, a weak attraction is found between the Cu atoms, possibly pointing toward cuprophilic interactions.