DOE OSTI2020
NaEu2AlP3 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 P3- atoms. There are a spread of Na–P bond distances ranging from 2.80–3.29 Å. In the second Na1+ site, Na1+ is bonded to four P3- atoms to form distorted NaP4 trigonal pyramids that share corners with four equivalent EuP6 octahedra, corners with two equivalent EuP7 pentagonal bipyramids, corners with five AlP4 tetrahedra, edges with two equivalent EuP6 octahedra, and faces with two equivalent EuP7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 48–89°. There are a spread of Na–P bond distances ranging from 2.66–3.14 Å. There are three inequivalent Eu+2.50+ sites. In the first Eu+2.50+ site, Eu+2.50+ is bonded to seven P3- atoms to form distorted EuP7 pentagonal bipyramids that share corners with seven EuP6 octahedra, corners with three AlP4 tetrahedra, a cornercorner with one NaP4 trigonal pyramid, edges with two EuP6 octahedra, edges with two equivalent EuP7 pentagonal bipyramids, edges with two AlP4 tetrahedra, a faceface with one EuP6 octahedra, faces with three equivalent EuP7 pentagonal bipyramids, and a faceface with one NaP4 trigonal pyramid. The corner-sharing octahedra tilt angles range from 27–52°. There are a spread of Eu–P bond distances ranging from 3.14–3.23 Å. In the second Eu+2.50+ site, Eu+2.50+ is bonded to six P3- atoms to form EuP6 octahedra that share corners with two equivalent EuP6 octahedra, corners with eight equivalent EuP7 pentagonal bipyramids, corners with two equivalent AlP4 tetrahedra, edges with two equivalent EuP6 octahedra, edges with two equivalent EuP7 pentagonal bipyramids, edges with two equivalent AlP4 tetrahedra, edges with two equivalent NaP4 trigonal pyramids, and faces with two equivalent EuP7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 38°. There are two shorter (2.96 Å) and four longer (3.13 Å) Eu–P bond lengths. In the third Eu+2.50+ site, Eu+2.50+ is bonded to six P3- atoms to form EuP6 octahedra that share corners with two equivalent EuP6 octahedra, corners with six equivalent EuP7 pentagonal bipyramids, corners with two equivalent AlP4 tetrahedra, corners with four equivalent NaP4 trigonal pyramids, edges with two equivalent EuP6 octahedra, edges with two equivalent EuP7 pentagonal bipyramids, and edges with four AlP4 tetrahedra. The corner-sharing octahedral tilt angles are 38°. There are a spread of Eu–P bond distances ranging from 2.99–3.12 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four P3- atoms to form AlP4 tetrahedra that share corners with four EuP6 octahedra, corners with two equivalent EuP7 pentagonal bipyramids, corners with two equivalent NaP4 trigonal pyramids, edges with two equivalent EuP6 octahedra, edges with two equivalent EuP7 pentagonal bipyramids, and edges with two AlP4 tetrahedra. The corner-sharing octahedral tilt angles are 52°. There are three shorter (2.38 Å) and one longer (2.46 Å) Al–P bond lengths. In the second Al3+ site, Al3+ is bonded to four P3- atoms to form AlP4 tetrahedra that share corners with four equivalent EuP7 pentagonal bipyramids, corners with three equivalent NaP4 trigonal pyramids, edges with four EuP6 octahedra, edges with two equivalent EuP7 pentagonal bipyramids, and an edgeedge with one AlP4 tetrahedra. There are a spread of Al–P bond distances ranging from 2.34–2.46 Å. There are five inequivalent P3- sites. In the first P3- site, P3- is bonded in a 7-coordinate geometry to two Na1+, three Eu+2.50+, and two Al3+ atoms. In the second P3- site, P3- is bonded in a 6-coordinate geometry to two equivalent Na1+, four Eu+2.50+, and two equivalent Al3+ atoms. In the third P3- site, P3- is bonded in a 1-coordinate geometry to six Eu+2.50+, one Al3+, and one P3- atom. The P–P bond length is 2.32 Å. In the fourth P3- site, P3- is bonded in a 8-coordinate geometry to three Na1+, four Eu+2.50+, and one Al3+ atom. In the fifth P3- site, P3- is bonded in a 8-coordinate geometry to one Na1+, six Eu+2.50+, and one P3- atom.