Materials Data on KMg6BO8 by Materials Project
KMg6BO8 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. K1+ is bonded to six O2- atoms to form KO6 octahedra that share corners with two equivalent MgO6 octahedra, corners with four equivalent KO6 octahedra, and edges with eight equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.24 Å) and two longer (2.35 Å) K–O bond lengths. There are three inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent KO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with eight equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (1.91 Å) and four longer (2.24 Å) Mg–O bond lengths. In the second Mg2+ site, Mg2+ is bonded in a distorted square co-planar geometry to four equivalent O2- atoms. All Mg–O bond lengths are 2.24 Å. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form distorted MgO6 octahedra that share corners with six equivalent MgO6 octahedra, edges with two equivalent KO6 octahedra, and edges with six MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–25°. There are a spread of Mg–O bond distances ranging from 1.96–2.31 Å. B3+ is bonded in a distorted linear geometry to six O2- atoms. There is two shorter (1.47 Å) and four longer (2.24 Å) B–O bond length. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded to one K1+ and five Mg2+ atoms to form distorted OKMg5 octahedra that share corners with six equivalent OKMg5 octahedra and edges with eight OK2Mg2B2 octahedra. The corner-sharing octahedra tilt angles range from 0–20°. In the second O2- site, O2- is bonded in a distorted single-bond geometry to four equivalent Mg2+ and one B3+ atom. In the third O2- site, O2- is bonded to two equivalent K1+, two equivalent Mg2+, and two equivalent B3+ atoms to form OK2Mg2B2 octahedra that share corners with six OK2Mg2B2 octahedra and edges with eight OKMg5 octahedra. The corner-sharing octahedral tilt angles are 0°. In the fourth O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six OK2Mg2B2 octahedra and edges with eight OKMg5 octahedra. The corner-sharing octahedral tilt angles are 0°. In the fifth O2- site, O2- is bonded to two equivalent K1+, two equivalent Mg2+, and two equivalent B3+ atoms to form OK2Mg2B2 octahedra that share corners with six OMg6 octahedra and edges with eight OKMg5 octahedra. The corner-sharing octahedral tilt angles are 0°. Both O–Mg bond lengths are 1.96 Å.