Materials Data on KMg3Cu(AsO4)3 by Materials Project
KMg3Cu(AsO4)3 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. K1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of K–O bond distances ranging from 2.67–3.00 Å. There are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form distorted MgO6 pentagonal pyramids that share corners with six AsO4 tetrahedra and edges with two equivalent MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.11–2.20 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six AsO4 tetrahedra, an edgeedge with one MgO6 octahedra, and an edgeedge with one MgO6 pentagonal pyramid. There are a spread of Mg–O bond distances ranging from 2.03–2.19 Å. Cu2+ is bonded in a square co-planar geometry to four O2- atoms. There is two shorter (1.95 Å) and two longer (1.97 Å) Cu–O bond length. 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 four equivalent MgO6 octahedra and corners with two equivalent MgO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 60–61°. There is two shorter (1.72 Å) and two longer (1.75 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 four equivalent MgO6 octahedra and corners with two equivalent MgO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 37–61°. There are a spread of As–O bond distances ranging from 1.70–1.74 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one K1+, two Mg2+, and one As5+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one K1+, two Mg2+, and one As5+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent K1+, one Mg2+, and one As5+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+, one Cu2+, and one As5+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+, one Cu2+, and one As5+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Mg2+ and one As5+ atom.