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

Abstract

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 crystallizesin perfect agreement with our structure mapin 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.