Materials Data on CaMgPO4F by Materials Project
CaMgPO4F crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Ca2+ is bonded in a 7-coordinate geometry to six O2- and one F1- atom. There are a spread of Ca–O bond distances ranging from 2.41–2.72 Å. The Ca–F bond length is 2.23 Å. Mg2+ is bonded to four O2- and two equivalent F1- atoms to form MgO4F2 octahedra that share corners with two equivalent MgO4F2 octahedra and corners with four equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 45°. There are two shorter (2.12 Å) and two longer (2.14 Å) Mg–O bond lengths. Both Mg–F bond lengths are 1.91 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with four equivalent MgO4F2 octahedra. The corner-sharing octahedra tilt angles range from 39–53°. All P–O bond lengths are 1.56 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Mg2+, and one P5+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Ca2+, one Mg2+, and one P5+ atom. F1- is bonded in a distorted trigonal planar geometry to one Ca2+ and two equivalent Mg2+ atoms.