DOE OSTI2020
Nb6Pd2Se15 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are six inequivalent Nb+4.33+ sites. In the first Nb+4.33+ site, Nb+4.33+ is bonded to seven Se2- atoms to form distorted NbSe7 pentagonal bipyramids that share edges with two NbSe7 pentagonal bipyramids, edges with two NbSe6 pentagonal pyramids, and faces with two NbSe7 pentagonal bipyramids. There are a spread of Nb–Se bond distances ranging from 2.62–2.82 Å. In the second Nb+4.33+ site, Nb+4.33+ is bonded to seven Se2- atoms to form distorted NbSe7 pentagonal bipyramids that share edges with two NbSe7 pentagonal bipyramids, edges with two NbSe6 pentagonal pyramids, and faces with two NbSe7 pentagonal bipyramids. There are a spread of Nb–Se bond distances ranging from 2.62–2.82 Å. In the third Nb+4.33+ site, Nb+4.33+ is bonded to seven Se2- atoms to form distorted NbSe7 pentagonal bipyramids that share edges with two NbSe7 pentagonal bipyramids, edges with two NbSe6 pentagonal pyramids, and faces with two NbSe7 pentagonal bipyramids. There are a spread of Nb–Se bond distances ranging from 2.64–2.79 Å. In the fourth Nb+4.33+ site, Nb+4.33+ is bonded to six Se2- atoms to form distorted NbSe6 pentagonal pyramids that share edges with two NbSe7 pentagonal bipyramids and edges with two NbSe6 pentagonal pyramids. There are a spread of Nb–Se bond distances ranging from 2.61–2.63 Å. In the fifth Nb+4.33+ site, Nb+4.33+ is bonded to six Se2- atoms to form distorted NbSe6 pentagonal pyramids that share edges with two NbSe7 pentagonal bipyramids and edges with two NbSe6 pentagonal pyramids. There are a spread of Nb–Se bond distances ranging from 2.60–2.64 Å. In the sixth Nb+4.33+ site, Nb+4.33+ is bonded to six Se2- atoms to form distorted NbSe6 pentagonal pyramids that share edges with two NbSe7 pentagonal bipyramids and edges with two NbSe6 pentagonal pyramids. There are a spread of Nb–Se bond distances ranging from 2.60–2.64 Å. There are three inequivalent Pd2+ sites. In the first Pd2+ site, Pd2+ is bonded in a square co-planar geometry to four Se2- atoms. There are two shorter (2.47 Å) and two longer (2.48 Å) Pd–Se bond lengths. In the second Pd2+ site, Pd2+ is bonded in a square co-planar geometry to four Se2- atoms. There are two shorter (2.47 Å) and two longer (2.48 Å) Pd–Se bond lengths. In the third Pd2+ site, Pd2+ is bonded in a distorted square co-planar geometry to four Se2- atoms. There are two shorter (2.62 Å) and two longer (2.63 Å) Pd–Se bond lengths. There are fifteen inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to two Nb+4.33+ and one Pd2+ atom. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to two Nb+4.33+ and one Pd2+ atom. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to two Nb+4.33+ and one Pd2+ atom. In the fourth Se2- site, Se2- is bonded in a 3-coordinate geometry to two Nb+4.33+ and one Pd2+ atom. In the fifth Se2- site, Se2- is bonded in a 3-coordinate geometry to two Nb+4.33+ and one Pd2+ atom. In the sixth Se2- site, Se2- is bonded in a 3-coordinate geometry to two Nb+4.33+ and one Pd2+ atom. In the seventh Se2- site, Se2- is bonded in a 3-coordinate geometry to three Nb+4.33+ atoms. In the eighth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Nb+4.33+ atoms. In the ninth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Nb+4.33+ atoms. In the tenth Se2- site, Se2- is bonded in a 4-coordinate geometry to three Nb+4.33+ and one Pd2+ atom. In the eleventh Se2- site, Se2- is bonded in a 4-coordinate geometry to three Nb+4.33+ and one Pd2+ atom. In the twelfth Se2- site, Se2- is bonded in a distorted trigonal non-coplanar geometry to three Nb+4.33+ atoms. In the thirteenth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Nb+4.33+ atoms. In the fourteenth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Nb+4.33+ atoms. In the fifteenth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Nb+4.33+ atoms.