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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Na2U2O7 by Materials Project

Na2U2O7 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to eight O2- atoms to form distorted NaO8 hexagonal bipyramids that share edges with two equivalent NaO8 hexagonal bipyramids, edges with two equivalent UO6 octahedra, edges with four equivalent NaO7 pentagonal bipyramids, and edges with four equivalent UO7 pentagonal bipyramids. There are a spread of Na–O bond distances ranging from 2.55–2.88 Å. In the second Na1+ site, Na1+ is bonded to seven O2- atoms to form distorted NaO7 pentagonal bipyramids that share corners with two equivalent UO6 octahedra, a cornercorner with one UO7 pentagonal bipyramid, edges with four equivalent NaO8 hexagonal bipyramids, edges with two equivalent UO6 octahedra, an edgeedge with one UO7 pentagonal bipyramid, and edges with two equivalent NaO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 52°. There are a spread of Na–O bond distances ranging from 2.41–2.72 Å. There are two inequivalent U6+ sites. In the first U6+ site, U6+ is bonded to seven O2- atoms to form distorted UO7 pentagonal bipyramids that share corners with two equivalent UO6 octahedra, a cornercorner with one NaO7 pentagonal bipyramid, edges with four equivalent NaO8 hexagonal bipyramids, edges with two equivalent UO6 octahedra, an edgeedge with one NaO7 pentagonal bipyramid, and edges with two equivalent UO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 39°. There are a spread of U–O bond distances ranging from 1.86–2.57 Å. In the second U6+ site, U6+ is bonded to six O2- atoms to form UO6 octahedra that share corners with two equivalent UO6 octahedra, corners with two equivalent NaO7 pentagonal bipyramids, corners with two equivalent UO7 pentagonal bipyramids, edges with two equivalent NaO8 hexagonal bipyramids, edges with two equivalent NaO7 pentagonal bipyramids, and edges with two equivalent UO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 51°. There are a spread of U–O bond distances ranging from 1.89–2.21 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to three Na1+ and one U6+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+ and three U6+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three Na1+ and one U6+ atom. In the fourth O2- site, O2- is bonded to one Na1+ and three U6+ atoms to form distorted ONaU3 trigonal pyramids that share corners with two equivalent ONaU3 trigonal pyramids and an edgeedge with one ONa3U tetrahedra. In the fifth O2- site, O2- is bonded to three Na1+ and one U6+ atom to form distorted ONa3U tetrahedra that share corners with two equivalent ONa3U tetrahedra and an edgeedge with one ONaU3 trigonal pyramid.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na2U2O7 by Materials Project

Na2U2O7 crystallizes in the monoclinic Pm space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Na–O bond distances ranging from 2.46–2.75 Å. In the second Na1+ site, Na1+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.61–2.82 Å. There are two inequivalent U6+ sites. In the first U6+ site, U6+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of U–O bond distances ranging from 1.87–2.50 Å. In the second U6+ site, U6+ is bonded to six O2- atoms to form distorted corner-sharing UO6 octahedra. The corner-sharing octahedral tilt angles are 43°. There are a spread of U–O bond distances ranging from 1.90–2.26 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to three Na1+ and one U6+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Na1+ and one U6+ atom. In the third O2- site, O2- is bonded to three Na1+ and one U6+ atom to form distorted corner-sharing ONa3U tetrahedra. In the fourth O2- site, O2- is bonded to three Na1+ and one U6+ atom to form distorted corner-sharing ONa3U tetrahedra. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+ and three U6+ atoms. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+ and three U6+ atoms. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+ and three U6+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na2U2O7 by Materials Project

Na2U2O7 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.37–2.84 Å. In the second Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 octahedra that share corners with four equivalent UO6 octahedra and corners with two equivalent UO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 54°. There are four shorter (2.41 Å) and two longer (2.87 Å) Na–O bond lengths. In the third Na1+ site, Na1+ is bonded in a 6-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.47–3.00 Å. There are two inequivalent U6+ sites. In the first U6+ site, U6+ is bonded to six O2- atoms to form UO6 octahedra that share corners with two equivalent NaO6 octahedra, corners with two equivalent UO6 octahedra, corners with two equivalent UO7 pentagonal bipyramids, and edges with two equivalent UO7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 51–54°. There are a spread of U–O bond distances ranging from 1.90–2.21 Å. In the second U6+ site, U6+ is bonded to seven O2- atoms to form distorted UO7 pentagonal bipyramids that share a cornercorner with one NaO6 octahedra, corners with two equivalent UO6 octahedra, edges with two equivalent UO6 octahedra, and edges with two equivalent UO7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 36–64°. There are a spread of U–O bond distances ranging from 1.87–2.59 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+ and three U6+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+ and three U6+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three Na1+ and one U6+ atom. In the fourth O2- site, O2- is bonded to three Na1+ and one U6+ atom to form a mixture of distorted edge and corner-sharing ONa3U tetrahedra. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to three Na1+ and one U6+ atom.

36 MATERIALS SCIENCE↗