DOE OSTI2020
Na2FeCd2(PO4)3 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.31–2.76 Å. In the second Na1+ site, Na1+ is bonded to eight O2- atoms to form distorted NaO8 hexagonal bipyramids that share corners with two equivalent PO4 tetrahedra, edges with two equivalent FeO6 octahedra, edges with three CdO6 octahedra, and edges with three PO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.58–2.83 Å. In the third Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.33–2.69 Å. Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six PO4 tetrahedra, an edgeedge with one NaO8 hexagonal bipyramid, and an edgeedge with one CdO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.98–2.17 Å. There are three inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded to six O2- atoms to form distorted CdO6 octahedra that share corners with six PO4 tetrahedra, an edgeedge with one NaO8 hexagonal bipyramid, an edgeedge with one FeO6 octahedra, and an edgeedge with one CdO6 octahedra. There are a spread of Cd–O bond distances ranging from 2.18–2.40 Å. In the second Cd2+ site, Cd2+ is bonded to six O2- atoms to form distorted CdO6 octahedra that share corners with six PO4 tetrahedra, an edgeedge with one NaO8 hexagonal bipyramid, and edges with two equivalent CdO6 octahedra. There are a spread of Cd–O bond distances ranging from 2.32–2.39 Å. In the third Cd2+ site, Cd2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Cd–O bond distances ranging from 2.31–2.88 Å. There are four inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent FeO6 octahedra and corners with four CdO6 octahedra. The corner-sharing octahedra tilt angles range from 49–61°. There is two shorter (1.55 Å) and two longer (1.57 Å) P–O bond length. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent FeO6 octahedra, corners with two equivalent CdO6 octahedra, and an edgeedge with one NaO8 hexagonal bipyramid. The corner-sharing octahedra tilt angles range from 47–54°. There is two shorter (1.53 Å) and two longer (1.58 Å) P–O bond length. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one NaO8 hexagonal bipyramid, corners with two equivalent FeO6 octahedra, and corners with three CdO6 octahedra. The corner-sharing octahedra tilt angles range from 35–62°. There are a spread of P–O bond distances ranging from 1.55–1.59 Å. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent FeO6 octahedra, corners with three CdO6 octahedra, and an edgeedge with one NaO8 hexagonal bipyramid. The corner-sharing octahedra tilt angles range from 40–64°. There are a spread of P–O bond distances ranging from 1.54–1.58 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Fe3+, and one P5+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, two Cd2+, and one P5+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to one Na1+, two Cd2+, and one P5+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, one Fe3+, one Cd2+, and one P5+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Cd2+, and one P5+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Fe3+, and one P5+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+, one Cd2+, and one P5+ atom. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+, one Cd2+, and one P5+ atom. In the ninth O2- site, O2- is bonded in a 1-coordinate geometry to one Fe3+, one Cd2+, and one P5+ atom. In the tenth O2- site, O2- is bonded in a 3-coordinate geometry to one Fe3+, one Cd2+, and one P5+ atom. In the eleventh O2- site, O2- is bonded in a 3-coordinate geometry to one Fe3+, one Cd2+, and one P5+ atom. In the twelfth O2- site, O2- is bonded in a 1-coordinate geometry to one Na1+, two Cd2+, and one P5+ atom.