DOE OSTI2020
Na3(NbSe2)4Na(NbSe2)2 crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of one Na(NbSe2)2 sheet oriented in the (0, 0, 1) direction and one Na3(NbSe2)4 sheet oriented in the (0, 0, 1) direction. In the Na(NbSe2)2 sheet, Na1+ is bonded in a 6-coordinate geometry to six Se2- atoms. All Na–Se bond lengths are 2.96 Å. There are two inequivalent Nb+3.33+ sites. In the first Nb+3.33+ site, Nb+3.33+ is bonded to six Se2- atoms to form distorted edge-sharing NbSe6 pentagonal pyramids. There are three shorter (2.62 Å) and three longer (2.65 Å) Nb–Se bond lengths. In the second Nb+3.33+ site, Nb+3.33+ is bonded to six Se2- atoms to form distorted edge-sharing NbSe6 pentagonal pyramids. There are three shorter (2.62 Å) and three longer (2.65 Å) Nb–Se bond lengths. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to three equivalent Na1+ and three equivalent Nb+3.33+ atoms to form a mixture of distorted corner, edge, and face-sharing SeNa3Nb3 pentagonal pyramids. The corner-sharing octahedral tilt angles are 41°. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Nb+3.33+ atoms. In the third Se2- site, Se2- is bonded to three equivalent Na1+ and three equivalent Nb+3.33+ atoms to form a mixture of corner, edge, and face-sharing SeNa3Nb3 octahedra. All Se–Nb bond lengths are 2.65 Å. In the fourth Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Nb+3.33+ atoms. All Se–Nb bond lengths are 2.62 Å. In the Na3(NbSe2)4 sheet, there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six Se2- atoms. All Na–Se bond lengths are 2.96 Å. In the second Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six Se2- atoms. There are three shorter (2.95 Å) and three longer (2.96 Å) Na–Se bond lengths. In the third Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six Se2- atoms. All Na–Se bond lengths are 2.96 Å. There are four inequivalent Nb+3.33+ sites. In the first Nb+3.33+ site, Nb+3.33+ is bonded to six Se2- atoms to form distorted edge-sharing NbSe6 pentagonal pyramids. All Nb–Se bond lengths are 2.64 Å. In the second Nb+3.33+ site, Nb+3.33+ is bonded to six Se2- atoms to form distorted edge-sharing NbSe6 pentagonal pyramids. There are three shorter (2.62 Å) and three longer (2.65 Å) Nb–Se bond lengths. In the third Nb+3.33+ site, Nb+3.33+ is bonded to six Se2- atoms to form distorted edge-sharing NbSe6 pentagonal pyramids. All Nb–Se bond lengths are 2.64 Å. In the fourth Nb+3.33+ site, Nb+3.33+ is bonded to six Se2- atoms to form distorted edge-sharing NbSe6 pentagonal pyramids. There are eight inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to three equivalent Na1+ and three equivalent Nb+3.33+ atoms to form a mixture of distorted corner, edge, and face-sharing SeNa3Nb3 pentagonal pyramids. The corner-sharing octahedral tilt angles are 41°. In the second Se2- site, Se2- is bonded to three equivalent Na1+ and three equivalent Nb+3.33+ atoms to form a mixture of distorted corner, edge, and face-sharing SeNa3Nb3 pentagonal pyramids. The corner-sharing octahedral tilt angles are 41°. In the third Se2- site, Se2- is bonded to three equivalent Na1+ and three equivalent Nb+3.33+ atoms to form a mixture of distorted corner, edge, and face-sharing SeNa3Nb3 pentagonal pyramids. The corner-sharing octahedral tilt angles are 41°. In the fourth Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Nb+3.33+ atoms. In the fifth Se2- site, Se2- is bonded to three equivalent Na1+ and three equivalent Nb+3.33+ atoms to form a mixture of corner, edge, and face-sharing SeNa3Nb3 octahedra. The corner-sharing octahedral tilt angles are 46°. In the sixth Se2- site, Se2- is bonded to three equivalent Na1+ and three equivalent Nb+3.33+ atoms to form a mixture of corner, edge, and face-sharing SeNa3Nb3 octahedra. In the seventh Se2- site, Se2- is bonded to three equivalent Na1+ and three equivalent Nb+3.33+ atoms to form a mixture of corner, edge, and face-sharing SeNa3Nb3 octahedra. The corner-sharing octahedral tilt angles are 46°. In the eighth Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Nb+3.33+ atoms.