DOE OSTI2020
Sc3As2 crystallizes in the tetragonal P4/m space group. The structure is three-dimensional. there are five inequivalent Sc2+ sites. In the first Sc2+ site, Sc2+ is bonded to five As3- atoms to form ScAs5 square pyramids that share corners with four equivalent ScAs6 octahedra, corners with four equivalent ScAs5 square pyramids, corners with four equivalent ScAs5 trigonal bipyramids, an edgeedge with one ScAs6 octahedra, edges with four equivalent ScAs5 square pyramids, edges with two equivalent ScAs5 trigonal bipyramids, and a faceface with one ScAs6 octahedra. The corner-sharing octahedra tilt angles range from 26–55°. There are a spread of Sc–As bond distances ranging from 2.65–2.87 Å. In the second Sc2+ site, Sc2+ is bonded to five As3- atoms to form distorted ScAs5 trigonal bipyramids that share corners with two equivalent ScAs6 octahedra, corners with four equivalent ScAs5 square pyramids, corners with four equivalent ScAs5 trigonal bipyramids, edges with two equivalent ScAs6 octahedra, edges with two equivalent ScAs5 square pyramids, and edges with four equivalent ScAs5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 49°. There are a spread of Sc–As bond distances ranging from 2.73–2.82 Å. In the third Sc2+ site, Sc2+ is bonded to six As3- atoms to form ScAs6 octahedra that share corners with eight equivalent ScAs5 square pyramids, corners with four equivalent ScAs5 trigonal bipyramids, edges with two equivalent ScAs6 octahedra, edges with two equivalent ScAs5 square pyramids, edges with four equivalent ScAs5 trigonal bipyramids, and faces with two equivalent ScAs5 square pyramids. There are two shorter (2.77 Å) and four longer (3.04 Å) Sc–As bond lengths. In the fourth Sc2+ site, Sc2+ is bonded in a square co-planar geometry to four equivalent As3- atoms. All Sc–As bond lengths are 2.69 Å. In the fifth Sc2+ site, Sc2+ is bonded in a square co-planar geometry to four equivalent As3- atoms. All Sc–As bond lengths are 2.92 Å. There are two inequivalent As3- sites. In the first As3- site, As3- is bonded to seven Sc2+ atoms to form a mixture of distorted edge, corner, and face-sharing AsSc7 pentagonal bipyramids. In the second As3- site, As3- is bonded in a 8-coordinate geometry to eight Sc2+ atoms.