Materials Data on KRbMg6O7 by Materials Project

RbKMg6O7 crystallizes in the tetragonal P4mm space group. The structure is two-dimensional and consists of one RbKMg6O7 sheet oriented in the (0, 0, 1) direction. Rb1+ is bonded in a 5-coordinate geometry to four equivalent O2- atoms. All Rb–O bond lengths are 2.67 Å. K1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are four shorter (2.51 Å) and one longer (3.17 Å) K–O bond lengths. There are four inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Mg–O bond lengths are 2.08 Å. In the second Mg2+ site, Mg2+ is bonded in a rectangular see-saw-like geometry to four equivalent O2- atoms. All Mg–O bond lengths are 2.08 Å. In the third Mg2+ site, Mg2+ is bonded in a square co-planar geometry to four O2- atoms. There are a spread of Mg–O bond distances ranging from 2.05–2.07 Å. In the fourth Mg2+ site, Mg2+ is bonded in a rectangular see-saw-like geometry to four O2- atoms. There are two shorter (2.07 Å) and two longer (2.08 Å) Mg–O bond lengths. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to four equivalent Mg2+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one K1+ and four equivalent Mg2+ atoms. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to four equivalent Mg2+ atoms. In the fourth O2- site, O2- is bonded to two equivalent K1+ and three Mg2+ atoms to form a mixture of corner and edge-sharing OK2Mg3 trigonal bipyramids. In the fifth O2- site, O2- is bonded to two equivalent Rb1+ and three Mg2+ atoms to form distorted ORb2Mg3 trigonal bipyramids that share corners with five OK2Mg3 trigonal bipyramids and edges with four equivalent ORb2Mg3 trigonal bipyramids.