DOE OSTI2020
NaSr2AlP3 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 2-coordinate geometry to six P+2.67- atoms. There are a spread of Na–P bond distances ranging from 2.90–3.31 Å. In the second Na1+ site, Na1+ is bonded in a distorted T-shaped geometry to three P+2.67- atoms. There are two shorter (2.75 Å) and one longer (3.02 Å) Na–P bond lengths. There are three inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded in a 7-coordinate geometry to seven P+2.67- atoms. There are a spread of Sr–P bond distances ranging from 3.09–3.47 Å. In the second Sr2+ site, Sr2+ is bonded to six P+2.67- atoms to form SrP6 octahedra that share corners with two equivalent SrP6 octahedra, corners with two equivalent AlP4 tetrahedra, edges with two equivalent SrP6 octahedra, and edges with two equivalent AlP4 tetrahedra. The corner-sharing octahedral tilt angles are 37°. There are two shorter (3.04 Å) and four longer (3.20 Å) Sr–P bond lengths. In the third Sr2+ site, Sr2+ is bonded to six P+2.67- atoms to form SrP6 octahedra that share corners with two equivalent SrP6 octahedra, corners with two equivalent AlP4 tetrahedra, edges with two equivalent SrP6 octahedra, and edges with four AlP4 tetrahedra. The corner-sharing octahedral tilt angles are 37°. There are a spread of Sr–P bond distances ranging from 3.06–3.21 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four P+2.67- atoms to form AlP4 tetrahedra that share edges with four SrP6 octahedra and an edgeedge with one AlP4 tetrahedra. There are a spread of Al–P bond distances ranging from 2.37–2.56 Å. In the second Al3+ site, Al3+ is bonded to four P+2.67- atoms to form AlP4 tetrahedra that share corners with four SrP6 octahedra, edges with two equivalent SrP6 octahedra, and edges with two AlP4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–52°. There are a spread of Al–P bond distances ranging from 2.37–2.45 Å. There are five inequivalent P+2.67- sites. In the first P+2.67- site, P+2.67- is bonded in a 7-coordinate geometry to two Na1+, three Sr2+, and two Al3+ atoms. In the second P+2.67- site, P+2.67- is bonded in a 8-coordinate geometry to three Na1+, four Sr2+, and one Al3+ atom. In the third P+2.67- site, P+2.67- is bonded in a 7-coordinate geometry to six Sr2+ and one P+2.67- atom. The P–P bond length is 2.28 Å. In the fourth P+2.67- site, P+2.67- is bonded in a 1-coordinate geometry to six Sr2+, one Al3+, and one P+2.67- atom. The P–P bond length is 2.27 Å. In the fifth P+2.67- site, P+2.67- is bonded in a 6-coordinate geometry to two equivalent Na1+, four Sr2+, and two equivalent Al3+ atoms.