DOE OSTI2020
SrZn2(AsO4)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Sr2+ is bonded to seven O2- atoms to form distorted SrO7 hexagonal pyramids that share corners with five ZnO4 tetrahedra, corners with five AsO4 tetrahedra, an edgeedge with one ZnO4 tetrahedra, and an edgeedge with one AsO4 tetrahedra. There are a spread of Sr–O bond distances ranging from 2.58–2.79 Å. There are two inequivalent Zn2+ sites. In the first Zn2+ site, Zn2+ is bonded to four O2- atoms to form ZnO4 tetrahedra that share corners with three equivalent SrO7 hexagonal pyramids and corners with four AsO4 tetrahedra. There are a spread of Zn–O bond distances ranging from 1.94–2.00 Å. In the second Zn2+ site, Zn2+ is bonded to four O2- atoms to form ZnO4 tetrahedra that share corners with two equivalent SrO7 hexagonal pyramids, corners with four AsO4 tetrahedra, and an edgeedge with one SrO7 hexagonal pyramid. There are a spread of Zn–O bond distances ranging from 1.96–2.02 Å. There are two inequivalent As5+ sites. In the first As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with two equivalent SrO7 hexagonal pyramids, corners with four ZnO4 tetrahedra, and an edgeedge with one SrO7 hexagonal pyramid. There is two shorter (1.72 Å) and two longer (1.73 Å) As–O bond length. In the second As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with three equivalent SrO7 hexagonal pyramids and corners with four ZnO4 tetrahedra. There is one shorter (1.71 Å) and three longer (1.73 Å) As–O bond length. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Sr2+, one Zn2+, and one As5+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Sr2+, one Zn2+, and one As5+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Sr2+, one Zn2+, and one As5+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Sr2+, one Zn2+, and one As5+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Sr2+, one Zn2+, and one As5+ atom. In the sixth O2- site, O2- is bonded in a trigonal planar geometry to one Sr2+, one Zn2+, and one As5+ atom. In the seventh O2- site, O2- is bonded in a bent 120 degrees geometry to one Zn2+ and one As5+ atom. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Sr2+, one Zn2+, and one As5+ atom.