Structure Prediction Using Our Semiempirical Structure Map: The Crystal Structure of the New Arsenide ZrTiAs

Recently, a novel structure map was presented for metal-rich pnictides and chalcogenides M2Q (M = valence-electron poor transition metal, Q = pnicogen or chalcogen). Herewith, we introduce ZrTiAs, which crystallizesin perfect agreement with our structure mapin the La2Sb type. While Zr2As apparently forms the Zr2P type, the (to date) hypothetical “Ti2As” could not have been prepared yet. ZrTiAs was obtained by arc-melting Zr, Ti, and TiAs2. This arsenide crystallizes in the tetragonal space group I4/mmm, with lattice dimensions of a = 379.28(6) pm, c = 1480.2(3) pm, and V = 212.94(7) 106 pm3 (Z = 4). In contrast to (Zr,Ti)Sb, ZrTiAs comprises complete ordering of the Zr and Ti atoms. However, the Zr atom in ZrTiAs may in part be replaced by Ti, i.e., a phase range of Zr1-δTi1+δAs exists with (at least) 0 ≤ δ ≤ 0.42(1). The ZrTiAs structure exhibits strong Zr−As, Ti−As, and Ti−Ti bonds, and to a minor extent Zr−Zr and Zr−Ti bonding interactions.