Synthesis and crystal structure of CaAgBi and BaAg1.837Bi2

Two ternary alkali earth silver bismuthides, CaAgBi and BaAg1.837Bi2, have been synthesized by solid-state reactions of the corresponding metals in welded Nb tubes at high temperature. Their structures have been established by single-crystal X-ray diffraction studies. CaAgBi crystallizes in the hexagonal space group P63mc (No.186) with cell parameters of a = b = 4.8113(4) Å, c = 7.8273(9) Å, V = 156.92(3) Å3, and Z = 2. BaAg1.837Bi2 belongs to tetragonal space group P4/nmm (No.129) with cell parameters of a = b = 4.9202(2) Å, c = 11.628(1) Å, V = 281.50(3) Å3, and Z = 2. The structure of CaAgBi is of the LiGaGe type, and features a three-dimensional four-connected (3D4C) anionic network with Ca2+ encapsulated in the channels formed by [Ag3Bi3] six-membered rings. BaAg1.837Bi2 is isostructural with CaBe2Ge2, a variant of the tetragonal ThCr2Si2-type structure. Its structure exhibits a three-dimensional anionic network built of (0 0 1) and (0 0 2) puckered [Ag2Bi2] layers interconnected via additional Ag–Bi bonds along the c-axis. BaAg1.837Bi2 is metallic based on band structure calculations.