Materials Data on Ca9Mg(PO4)7 by Materials Project
Ca9Mg(PO4)7 crystallizes in the trigonal R3c space group. The structure is three-dimensional. there are three inequivalent Ca sites. In the first Ca site, Ca is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Ca–O bond distances ranging from 2.39–2.98 Å. In the second Ca site, Ca is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Ca–O bond distances ranging from 2.34–2.78 Å. In the third Ca site, Ca is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Ca–O bond distances ranging from 2.38–2.67 Å. Mg is bonded to six O atoms to form MgO6 octahedra that share corners with six PO4 tetrahedra. There are three shorter (2.08 Å) and three longer (2.10 Å) Mg–O bond lengths. There are three inequivalent P sites. In the first P site, P is bonded to four O atoms to form PO4 tetrahedra that share a cornercorner with one MgO6 octahedra. The corner-sharing octahedral tilt angles are 44°. There are a spread of P–O bond distances ranging from 1.54–1.57 Å. In the second P site, P is bonded in a tetrahedral geometry to four O atoms. All P–O bond lengths are 1.56 Å. In the third P site, P is bonded to four O atoms to form PO4 tetrahedra that share a cornercorner with one MgO6 octahedra. The corner-sharing octahedral tilt angles are 46°. There are a spread of P–O bond distances ranging from 1.54–1.57 Å. There are ten inequivalent O sites. In the first O site, O is bonded in a 4-coordinate geometry to two equivalent Ca, one Mg, and one P atom. In the second O site, O is bonded in a single-bond geometry to one P atom. In the third O site, O is bonded in a 1-coordinate geometry to three Ca and one P atom. In the fourth O site, O is bonded in a 1-coordinate geometry to three Ca and one P atom. In the fifth O site, O is bonded in a 1-coordinate geometry to three Ca and one P atom. In the sixth O site, O is bonded in a 3-coordinate geometry to two Ca and one P atom. In the seventh O site, O is bonded in a 1-coordinate geometry to three Ca and one P atom. In the eighth O site, O is bonded in a 1-coordinate geometry to three Ca and one P atom. In the ninth O site, O is bonded in a 4-coordinate geometry to two equivalent Ca, one Mg, and one P atom. In the tenth O site, O is bonded in a 1-coordinate geometry to three Ca and one P atom.