Materials Data on KAlAs2O7 by Materials Project
KAlAs2O7 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to eight O2- atoms to form distorted KO8 hexagonal bipyramids that share corners with two equivalent AlO6 octahedra, corners with six AsO4 tetrahedra, edges with two equivalent AlO6 octahedra, and edges with two equivalent AsO4 tetrahedra. The corner-sharing octahedral tilt angles are 52°. There are a spread of K–O bond distances ranging from 2.82–3.20 Å. In the second K1+ site, K1+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of K–O bond distances ranging from 2.81–3.30 Å. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one KO8 hexagonal bipyramid, corners with six AsO4 tetrahedra, and an edgeedge with one KO8 hexagonal bipyramid. There are a spread of Al–O bond distances ranging from 1.90–1.95 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 a cornercorner with one KO8 hexagonal bipyramid, corners with three equivalent AlO6 octahedra, a cornercorner with one AsO4 tetrahedra, and an edgeedge with one KO8 hexagonal bipyramid. The corner-sharing octahedra tilt angles range from 42–49°. There are a spread of As–O bond distances ranging from 1.69–1.82 Å. In the second As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with two equivalent KO8 hexagonal bipyramids, corners with three equivalent AlO6 octahedra, and a cornercorner with one AsO4 tetrahedra. The corner-sharing octahedra tilt angles range from 34–52°. There are a spread of As–O bond distances ranging from 1.69–1.80 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two K1+, one Al3+, and one As5+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two K1+, one Al3+, and one As5+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Al3+, and one As5+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one K1+ and two As5+ atoms. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+, one Al3+, and one As5+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+, one Al3+, and one As5+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one K1+, one Al3+, and one As5+ atom.