DOI: 10.17188/1269393
title: Materials Data on KNa7Pb2O7 by Materials Project

description: KNa7Pb2O7 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. K1+ is bonded to six O2- atoms to form distorted KO6 octahedra that share corners with two equivalent KO6 octahedra, corners with two equivalent PbO4 tetrahedra, corners with four NaO4 tetrahedra, a cornercorner with one NaO4 trigonal pyramid, edges with three equivalent KO6 octahedra, edges with two equivalent PbO4 tetrahedra, and edges with four NaO4 tetrahedra. The corner-sharing octahedral tilt angles are 7°. There are a spread of K–O bond distances ranging from 2.73–3.04 Å. There are seven inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to four O2- atoms to form NaO4 trigonal pyramids that share a cornercorner with one PbO4 tetrahedra, corners with two equivalent NaO4 tetrahedra, corners with three equivalent NaO4 trigonal pyramids, and edges with two equivalent NaO4 trigonal pyramids. There are a spread of Na–O bond distances ranging from 2.31–2.44 Å. In the second Na1+ site, Na1+ is bonded to four O2- atoms to form NaO4 tetrahedra that share corners with three equivalent KO6 octahedra, corners with two equivalent NaO4 tetrahedra, corners with four equivalent PbO4 tetrahedra, a cornercorner with one NaO4 trigonal pyramid, edges with three equivalent KO6 octahedra, and an edgeedge with one NaO4 tetrahedra. The corner-sharing octahedra tilt angles range from 20–87°. There are a spread of Na–O bond distances ranging from 2.36–2.42 Å. In the third Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.33–2.97 Å. In the fourth Na1+ site, Na1+ is bonded to four O2- atoms to form NaO4 tetrahedra that share a cornercorner with one KO6 octahedra, corners with two equivalent NaO4 tetrahedra, corners with three equivalent PbO4 tetrahedra, corners with five NaO4 trigonal pyramids, an edgeedge with one KO6 octahedra, and an edgeedge with one NaO4 trigonal pyramid. The corner-sharing octahedral tilt angles are 33°. There are a spread of Na–O bond distances ranging from 2.30–2.44 Å. In the fifth Na1+ site, Na1+ is bonded to four O2- atoms to form NaO4 trigonal pyramids that share a cornercorner with one PbO4 tetrahedra, a cornercorner with one NaO4 trigonal pyramid, an edgeedge with one NaO4 tetrahedra, and edges with three NaO4 trigonal pyramids. There are a spread of Na–O bond distances ranging from 2.37–2.46 Å. In the sixth Na1+ site, Na1+ is bonded in a trigonal planar geometry to three O2- atoms. There are one shorter (2.34 Å) and two longer (2.35 Å) Na–O bond lengths. In the seventh Na1+ site, Na1+ is bonded to four O2- atoms to form NaO4 trigonal pyramids that share a cornercorner with one KO6 octahedra, corners with two equivalent PbO4 tetrahedra, corners with four NaO4 tetrahedra, corners with four NaO4 trigonal pyramids, and an edgeedge with one NaO4 trigonal pyramid. The corner-sharing octahedral tilt angles are 21°. There are a spread of Na–O bond distances ranging from 2.35–2.46 Å. There are two inequivalent Pb3+ sites. In the first Pb3+ site, Pb3+ is bonded in a distorted T-shaped geometry to three O2- atoms. There are a spread of Pb–O bond distances ranging from 2.21–2.23 Å. In the second Pb3+ site, Pb3+ is bonded to four O2- atoms to form PbO4 tetrahedra that share corners with two equivalent KO6 octahedra, corners with seven NaO4 tetrahedra, corners with four NaO4 trigonal pyramids, and edges with two equivalent KO6 octahedra. The corner-sharing octahedra tilt angles range from 35–79°. There are two shorter (2.11 Å) and two longer (2.12 Å) Pb–O bond lengths. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent K1+, two Na1+, and one Pb3+ atom. In the second O2- site, O2- is bonded to five Na1+ and one Pb3+ atom to form a mixture of corner, edge, and face-sharing ONa5Pb octahedra. The corner-sharing octahedra tilt angles range from 41–58°. In the third O2- site, O2- is bonded to three equivalent K1+, two equivalent Na1+, and one Pb3+ atom to form a mixture of distorted corner and edge-sharing OK3Na2Pb octahedra. The corner-sharing octahedra tilt angles range from 7–70°. In the fourth O2- site, O2- is bonded in a 6-coordinate geometry to one K1+, four Na1+, and one Pb3+ atom. In the fifth O2- site, O2- is bonded to five Na1+ and one Pb3+ atom to form distorted ONa5Pb octahedra that share corners with four OK3Na2Pb octahedra, edges with three ONa5Pb octahedra, and a faceface with one ONa5Pb octahedra. The corner-sharing octahedra tilt angles range from 41–70°. In the sixth O2- site, O2- is bonded to five Na1+ and one Pb3+ atom to form a mixture of corner and edge-sharing ONa5Pb octahedra. The corner-sharing octahedra tilt angles range from 41–63°. In the seventh O2- site, O2- is bonded to five Na1+ and one Pb3+ atom to form a mixture of corner and edge-sharing ONa5Pb octahedra. The corner-sharing octahedra tilt angles range from 41–63°.