Two new titanium molybdenum arsenides:: Ti2MoAs2 and Ti3MoAs3, ternary substitution variants Of V3As2 and β-V4As3

The title compounds were prepared by arc-melting pre-annealed mixtures of Ti, Mo, and As. Both Ti2MoAs2 and Ti3MoAs3 adopt structures formed by the corresponding binary vanadium arsenides, V3As2 and beta-V4As3. Ti2MoAs2 crystallizes in the tetragonal space group P4/m, with a = 9.706(4) angstrom, c = 3.451(2) angstrom, V = 325.1(3) angstrom(3) (Z = 4), and Ti3MoAs3 in the monoclinic space group C2/m, with a = 14.107(3) angstrom, b = 3.5148(7) angstrom, c = 9.522(2) angstrom, beta = 100.66(3)degrees, V = 464.0(2) angstrom(3) (Z = 4). In both cases, the metal atoms form infinite chains of trans edge-condensed octahedra, and the As atoms are located in (capped) trigonal prismatic voids. While most metal atom sites exhibit mixed Ti/Mo occupancies, the Mo atoms prefer the sites with more metal atom and fewer As atom neighbors. Ti2MoAs2 and Ti3MoAs3 are metallic entropy-stabilized materials that decompose upon annealing at intermediate temperatures. (C) 2005 Elsevier Inc. All rights reserved.