DOE OSTI2020
Na2CuO2 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. there are eight inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 5-coordinate geometry to four O2- atoms. There are a spread of Na–O bond distances ranging from 2.28–2.78 Å. In the second Na1+ site, Na1+ is bonded in a distorted trigonal planar geometry to three O2- atoms. There are a spread of Na–O bond distances ranging from 2.24–2.43 Å. In the third 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 2.31–2.88 Å. In the fourth Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 trigonal pyramids that share corners with two CuO4 trigonal pyramids and an edgeedge with one CuO4 trigonal pyramid. There are a spread of Na–O bond distances ranging from 2.21–2.43 Å. In the fifth Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 trigonal pyramids that share corners with two CuO4 trigonal pyramids and an edgeedge with one CuO4 trigonal pyramid. There are a spread of Na–O bond distances ranging from 2.24–2.37 Å. In the sixth 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 2.35–2.82 Å. In the seventh Na1+ site, Na1+ is bonded in a distorted rectangular see-saw-like geometry to four O2- atoms. There are a spread of Na–O bond distances ranging from 2.31–2.58 Å. In the eighth Na1+ site, Na1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Na–O bond distances ranging from 2.26–2.72 Å. There are four inequivalent Cu2+ sites. In the first Cu2+ site, Cu2+ is bonded in a distorted trigonal planar geometry to three O2- atoms. There are a spread of Cu–O bond distances ranging from 1.85–1.94 Å. In the second Cu2+ site, Cu2+ is bonded to four O2- atoms to form distorted CuO4 trigonal pyramids that share corners with two NaO4 trigonal pyramids, an edgeedge with one NaO4 trigonal pyramid, and an edgeedge with one CuO4 trigonal pyramid. There are a spread of Cu–O bond distances ranging from 1.92–2.05 Å. In the third Cu2+ site, Cu2+ is bonded to four O2- atoms to form distorted CuO4 trigonal pyramids that share corners with two NaO4 trigonal pyramids, an edgeedge with one NaO4 trigonal pyramid, and an edgeedge with one CuO4 trigonal pyramid. There are a spread of Cu–O bond distances ranging from 1.92–2.02 Å. In the fourth Cu2+ site, Cu2+ is bonded in a distorted trigonal planar geometry to three O2- atoms. There are a spread of Cu–O bond distances ranging from 1.84–1.93 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded to five Na1+ and one Cu2+ atom to form distorted ONa5Cu octahedra that share corners with four ONa5Cu octahedra and an edgeedge with one ONa4Cu2 octahedra. The corner-sharing octahedra tilt angles range from 33–49°. In the second O2- site, O2- is bonded to four Na1+ and two Cu2+ atoms to form a mixture of distorted corner and edge-sharing ONa4Cu2 octahedra. The corner-sharing octahedra tilt angles range from 33–70°. In the third O2- site, O2- is bonded in a 6-coordinate geometry to four Na1+ and two Cu2+ atoms. In the fourth O2- site, O2- is bonded in a 5-coordinate geometry to three Na1+ and two Cu2+ atoms. In the fifth O2- site, O2- is bonded in a 5-coordinate geometry to three Na1+ and two Cu2+ atoms. In the sixth O2- site, O2- is bonded in a 7-coordinate geometry to five Na1+ and two Cu2+ atoms. In the seventh O2- site, O2- is bonded in a 6-coordinate geometry to four Na1+ and two Cu2+ atoms. In the eighth O2- site, O2- is bonded to five Na1+ and one Cu2+ atom to form distorted corner-sharing ONa5Cu octahedra. The corner-sharing octahedral tilt angles are 49°.