DOE OSTI2020
Na3Pr(AsO4)2 crystallizes in the orthorhombic Pca2_1 space group. The structure is three-dimensional. there are six 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 2.34–2.87 Å. In the second 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 2.30–2.91 Å. In the third Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 octahedra that share corners with six AsO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.31–2.60 Å. In the fourth Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.30–2.71 Å. In the fifth 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 2.39–2.86 Å. In the sixth Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 octahedra that share corners with six AsO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.31–2.61 Å. There are two inequivalent Pr3+ sites. In the first Pr3+ site, Pr3+ is bonded in a 7-coordinate geometry to eight O2- atoms. There are a spread of Pr–O bond distances ranging from 2.39–3.01 Å. In the second Pr3+ site, Pr3+ is bonded in a 7-coordinate geometry to eight O2- atoms. There are a spread of Pr–O bond distances ranging from 2.40–2.99 Å. There are four inequivalent As5+ sites. In the first As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with three NaO6 octahedra. The corner-sharing octahedra tilt angles range from 44–69°. There is one shorter (1.71 Å) and three longer (1.73 Å) As–O bond length. In the second As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with three NaO6 octahedra. The corner-sharing octahedra tilt angles range from 8–38°. All As–O bond lengths are 1.72 Å. In the third As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with three NaO6 octahedra. The corner-sharing octahedra tilt angles range from 8–38°. There is three shorter (1.72 Å) and one longer (1.73 Å) As–O bond length. In the fourth As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with three NaO6 octahedra. The corner-sharing octahedra tilt angles range from 45–68°. There are a spread of As–O bond distances ranging from 1.71–1.74 Å. There are sixteen inequivalent O2- sites. In the first O2- site, O2- is bonded to three Na1+ and one As5+ atom to form distorted corner-sharing ONa3As tetrahedra. In the second O2- site, O2- is bonded in a 1-coordinate geometry to four Na1+, one Pr3+, and one As5+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one Na1+, one Pr3+, and one As5+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to three Na1+, one Pr3+, and one As5+ atom. In the fifth O2- site, O2- is bonded to two Na1+, one Pr3+, and one As5+ atom to form distorted corner-sharing ONa2PrAs tetrahedra. In the sixth O2- site, O2- is bonded to three Na1+ and one As5+ atom to form distorted corner-sharing ONa3As tetrahedra. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to three Na1+, one Pr3+, and one As5+ atom. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Na1+, one Pr3+, and one As5+ atom. In the ninth O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, two Pr3+, and one As5+ atom. In the tenth O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, two Pr3+, and one As5+ atom. In the eleventh O2- site, O2- is bonded to two Na1+, one Pr3+, and one As5+ atom to form distorted corner-sharing ONa2PrAs tetrahedra. In the twelfth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Pr3+, and one As5+ atom. In the thirteenth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Pr3+, and one As5+ atom. In the fourteenth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Pr3+, and one As5+ atom. In the fifteenth O2- site, O2- is bonded in a 1-coordinate geometry to three Na1+, one Pr3+, and one As5+ atom. In the sixteenth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Pr3+, and one As5+ atom.