DOE OSTI2020
Ca2Mn3Si3O14 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to seven O2- atoms to form distorted CaO7 pentagonal bipyramids that share corners with five SiO4 tetrahedra, an edgeedge with one CaO6 octahedra, edges with four MnO6 octahedra, and an edgeedge with one SiO4 tetrahedra. There are a spread of Ca–O bond distances ranging from 2.29–2.61 Å. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with two equivalent MnO6 octahedra, corners with six SiO4 tetrahedra, edges with two equivalent MnO6 octahedra, and an edgeedge with one CaO7 pentagonal bipyramid. The corner-sharing octahedral tilt angles are 58°. There are a spread of Ca–O bond distances ranging from 2.18–2.62 Å. There are three inequivalent Mn4+ sites. In the first Mn4+ site, Mn4+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with four SiO4 tetrahedra, edges with two equivalent MnO6 octahedra, and edges with two equivalent CaO7 pentagonal bipyramids. There are a spread of Mn–O bond distances ranging from 1.90–2.12 Å. In the second Mn4+ site, Mn4+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with four SiO4 tetrahedra, edges with two equivalent CaO6 octahedra, edges with two equivalent MnO6 octahedra, and edges with two equivalent CaO7 pentagonal bipyramids. There are a spread of Mn–O bond distances ranging from 1.88–2.18 Å. In the third Mn4+ site, Mn4+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with two equivalent CaO6 octahedra, corners with four SiO4 tetrahedra, and edges with two equivalent MnO6 octahedra. The corner-sharing octahedral tilt angles are 58°. There are a spread of Mn–O bond distances ranging from 1.91–1.98 Å. There are three inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two equivalent MnO6 octahedra, corners with three equivalent CaO6 octahedra, corners with three equivalent CaO7 pentagonal bipyramids, and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 32–65°. There are a spread of Si–O bond distances ranging from 1.59–1.70 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one CaO6 octahedra, corners with six MnO6 octahedra, and corners with two equivalent CaO7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 50–68°. There are a spread of Si–O bond distances ranging from 1.62–1.70 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two equivalent CaO6 octahedra, corners with four MnO6 octahedra, a cornercorner with one SiO4 tetrahedra, and an edgeedge with one CaO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 49–63°. There is two shorter (1.63 Å) and two longer (1.65 Å) Si–O bond length. There are eleven inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to one Ca2+, one Mn4+, and one Si4+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one Mn4+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, two equivalent Mn4+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Ca2+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to one Ca2+ and two Si4+ atoms. In the sixth O2- site, O2- is bonded in a water-like geometry to two equivalent Mn4+ atoms. In the seventh O2- site, O2- is bonded in a water-like geometry to two equivalent Mn4+ atoms. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Mn4+ and one Si4+ atom. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to two Ca2+, one Mn4+, and one Si4+ atom. In the tenth O2- site, O2- is bonded in a trigonal non-coplanar geometry to one Ca2+ and two equivalent Mn4+ atoms. In the eleventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+, two equivalent Mn4+, and one Si4+ atom.