DOE OSTI2020
Ba3Zn2As4 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded to seven As+2.50- atoms to form BaAs7 pentagonal bipyramids that share corners with six equivalent BaAs6 octahedra, corners with seven equivalent ZnAs4 tetrahedra, an edgeedge with one BaAs6 octahedra, edges with four equivalent BaAs7 pentagonal bipyramids, edges with three equivalent ZnAs4 tetrahedra, a faceface with one BaAs6 octahedra, and faces with three equivalent BaAs7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 35–53°. There are a spread of Ba–As bond distances ranging from 3.38–3.61 Å. In the second Ba2+ site, Ba2+ is bonded to six As+2.50- atoms to form BaAs6 octahedra that share corners with twelve equivalent BaAs7 pentagonal bipyramids, corners with two equivalent ZnAs4 tetrahedra, edges with two equivalent BaAs6 octahedra, edges with two equivalent BaAs7 pentagonal bipyramids, edges with four equivalent ZnAs4 tetrahedra, and faces with two equivalent BaAs7 pentagonal bipyramids. There are two shorter (3.25 Å) and four longer (3.32 Å) Ba–As bond lengths. Zn2+ is bonded to four As+2.50- atoms to form ZnAs4 tetrahedra that share a cornercorner with one BaAs6 octahedra, corners with seven equivalent BaAs7 pentagonal bipyramids, corners with two equivalent ZnAs4 tetrahedra, edges with two equivalent BaAs6 octahedra, edges with three equivalent BaAs7 pentagonal bipyramids, and edges with two equivalent ZnAs4 tetrahedra. The corner-sharing octahedral tilt angles are 40°. There are a spread of Zn–As bond distances ranging from 2.60–2.71 Å. There are two inequivalent As+2.50- sites. In the first As+2.50- site, As+2.50- is bonded in a 7-coordinate geometry to four Ba2+ and three equivalent Zn2+ atoms. In the second As+2.50- site, As+2.50- is bonded in a 8-coordinate geometry to six Ba2+, one Zn2+, and one As+2.50- atom. The As–As bond length is 2.52 Å.