DOE OSTI2020
Ta6Mn2FeO18 is beta Vanadium nitride-derived structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are six inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share a cornercorner with one MnO6 octahedra, corners with three equivalent FeO6 octahedra, corners with four TaO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one MnO6 octahedra. The corner-sharing octahedra tilt angles range from 40–54°. There are a spread of Ta–O bond distances ranging from 1.99–2.03 Å. In the second Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with two equivalent MnO6 octahedra, corners with two equivalent FeO6 octahedra, corners with four TaO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one MnO6 octahedra. The corner-sharing octahedra tilt angles range from 41–54°. There are a spread of Ta–O bond distances ranging from 1.98–2.03 Å. In the third Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share a cornercorner with one MnO6 octahedra, corners with three equivalent FeO6 octahedra, corners with four TaO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one MnO6 octahedra. The corner-sharing octahedra tilt angles range from 41–54°. There are a spread of Ta–O bond distances ranging from 1.99–2.03 Å. In the fourth Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra, corners with four MnO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one MnO6 octahedra. The corner-sharing octahedra tilt angles range from 40–55°. There are three shorter (2.00 Å) and three longer (2.01 Å) Ta–O bond lengths. In the fifth Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra, corners with four MnO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 40–54°. There are a spread of Ta–O bond distances ranging from 1.99–2.02 Å. In the sixth Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra, corners with four MnO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 41–54°. There are a spread of Ta–O bond distances ranging from 1.98–2.03 Å. There are three inequivalent Mn2+ sites. In the first Mn2+ site, Mn2+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with eight TaO6 octahedra and edges with two TaO6 octahedra. The corner-sharing octahedra tilt angles range from 51–54°. There are a spread of Mn–O bond distances ranging from 2.17–2.22 Å. In the second Mn2+ site, Mn2+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with eight TaO6 octahedra and edges with two equivalent TaO6 octahedra. The corner-sharing octahedra tilt angles range from 52–55°. There are a spread of Mn–O bond distances ranging from 2.17–2.23 Å. In the third Mn2+ site, Mn2+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with eight TaO6 octahedra and edges with two equivalent TaO6 octahedra. The corner-sharing octahedra tilt angles range from 51–54°. There are two shorter (2.17 Å) and four longer (2.22 Å) Mn–O bond lengths. Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with eight TaO6 octahedra and edges with two TaO6 octahedra. The corner-sharing octahedra tilt angles range from 50–54°. There are a spread of Fe–O bond distances ranging from 2.12–2.22 Å. There are fourteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the tenth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the eleventh O2- site, O2- is bonded in a trigonal planar geometry to two equivalent Ta5+ and one Mn2+ atom. In the twelfth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the thirteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ta5+ and one Fe2+ atom. In the fourteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Fe2+ atom.