Materials Data on Na2NiO2 by Materials Project
Na2NiO2 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first 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 2.31–2.38 Å. In the second Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are two shorter (2.33 Å) and three longer (2.55 Å) Na–O bond lengths. Ni2+ is bonded in a square co-planar geometry to four O2- atoms. There is two shorter (1.92 Å) and two longer (1.93 Å) Ni–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 7-coordinate geometry to five Na1+ and two equivalent Ni2+ atoms. In the second O2- site, O2- is bonded to four Na1+ and two equivalent Ni2+ atoms to form a mixture of corner and edge-sharing ONa4Ni2 octahedra. The corner-sharing octahedral tilt angles are 54°.