DOE OSTI2020
Mg3Ti4P6O24 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to five O2- atoms to form MgO5 trigonal bipyramids that share a cornercorner with one MgO6 octahedra, corners with five PO4 tetrahedra, and edges with two TiO6 octahedra. The corner-sharing octahedral tilt angles are 64°. There are a spread of Mg–O bond distances ranging from 2.01–2.15 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent TiO6 octahedra, corners with six PO4 tetrahedra, and corners with two equivalent MgO5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 63°. There are two shorter (2.06 Å) and four longer (2.23 Å) Mg–O bond lengths. There are two inequivalent Ti3+ sites. In the first Ti3+ site, Ti3+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with six PO4 tetrahedra, an edgeedge with one TiO6 octahedra, and an edgeedge with one MgO5 trigonal bipyramid. There are a spread of Ti–O bond distances ranging from 1.93–2.18 Å. In the second Ti3+ site, Ti3+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one MgO6 octahedra, corners with six PO4 tetrahedra, an edgeedge with one TiO6 octahedra, and an edgeedge with one MgO5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 63°. There are a spread of Ti–O bond distances ranging from 1.94–2.17 Å. There are three inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one MgO6 octahedra, corners with five TiO6 octahedra, and a cornercorner with one MgO5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 20–57°. There are a spread of P–O bond distances ranging from 1.50–1.58 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one MgO6 octahedra, corners with three TiO6 octahedra, and corners with two equivalent MgO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 25–58°. There are a spread of P–O bond distances ranging from 1.53–1.57 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one MgO6 octahedra, corners with four TiO6 octahedra, and corners with two equivalent MgO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 32–61°. There are a spread of P–O bond distances ranging from 1.53–1.57 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+, one Ti3+, and one P5+ atom. In the second O2- site, O2- is bonded in a trigonal planar geometry to two Mg2+ and one P5+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Ti3+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ti3+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ti3+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to one Ti3+ and one P5+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+, one Ti3+, and one P5+ atom. In the eighth O2- site, O2- is bonded in a trigonal planar geometry to one Mg2+, one Ti3+, and one P5+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mg2+ and one P5+ atom. In the tenth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+, one Ti3+, and one P5+ atom. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Ti3+ and one P5+ atom. In the twelfth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+, one Ti3+, and one P5+ atom.