DOE OSTI2020
Na5AuSe12 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. there are five inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six Se+0.83- atoms to form a mixture of distorted edge and corner-sharing NaSe6 octahedra. There are a spread of Na–Se bond distances ranging from 3.00–3.61 Å. In the second Na1+ site, Na1+ is bonded to five Se+0.83- atoms to form distorted NaSe5 trigonal bipyramids that share corners with two equivalent NaSe6 octahedra, an edgeedge with one NaSe6 octahedra, and an edgeedge with one NaSe5 square pyramid. The corner-sharing octahedra tilt angles range from 25–26°. There are a spread of Na–Se bond distances ranging from 2.87–3.20 Å. In the third Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five Se+0.83- atoms. There are a spread of Na–Se bond distances ranging from 2.95–3.48 Å. In the fourth Na1+ site, Na1+ is bonded to five Se+0.83- atoms to form NaSe5 square pyramids that share corners with two equivalent NaSe6 octahedra, an edgeedge with one NaSe6 octahedra, and an edgeedge with one NaSe5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 24–25°. There are a spread of Na–Se bond distances ranging from 2.96–3.08 Å. In the fifth Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six Se+0.83- atoms. There are a spread of Na–Se bond distances ranging from 2.87–3.51 Å. Au5+ is bonded in a rectangular see-saw-like geometry to four Se+0.83- atoms. There are three shorter (2.55 Å) and one longer (2.56 Å) Au–Se bond lengths. There are twelve inequivalent Se+0.83- sites. In the first Se+0.83- site, Se+0.83- is bonded in a 5-coordinate geometry to four Na1+ and one Se+0.83- atom. The Se–Se bond length is 2.39 Å. In the second Se+0.83- site, Se+0.83- is bonded in a 2-coordinate geometry to two Na1+, one Au5+, and one Se+0.83- atom. The Se–Se bond length is 2.42 Å. In the third Se+0.83- site, Se+0.83- is bonded in a 5-coordinate geometry to four Na1+ and one Se+0.83- atom. The Se–Se bond length is 2.38 Å. In the fourth Se+0.83- site, Se+0.83- is bonded in a 4-coordinate geometry to two Na1+, one Au5+, and two Se+0.83- atoms. There are one shorter (2.40 Å) and one longer (3.76 Å) Se–Se bond lengths. In the fifth Se+0.83- site, Se+0.83- is bonded in a 5-coordinate geometry to three Na1+, one Au5+, and two Se+0.83- atoms. There are one shorter (2.40 Å) and one longer (3.17 Å) Se–Se bond lengths. In the sixth Se+0.83- site, Se+0.83- is bonded in a 2-coordinate geometry to two Na1+, one Au5+, and one Se+0.83- atom. The Se–Se bond length is 2.41 Å. In the seventh Se+0.83- site, Se+0.83- is bonded in a 2-coordinate geometry to two Se+0.83- atoms. In the eighth Se+0.83- site, Se+0.83- is bonded in a 2-coordinate geometry to two Se+0.83- atoms. The Se–Se bond length is 2.40 Å. In the ninth Se+0.83- site, Se+0.83- is bonded in a 4-coordinate geometry to four Na1+ and one Se+0.83- atom. The Se–Se bond length is 2.41 Å. In the tenth Se+0.83- site, Se+0.83- is bonded in a 3-coordinate geometry to one Na1+ and two Se+0.83- atoms. In the eleventh Se+0.83- site, Se+0.83- is bonded in a 2-coordinate geometry to one Na1+ and four Se+0.83- atoms. In the twelfth Se+0.83- site, Se+0.83- is bonded in a 5-coordinate geometry to four Na1+ and one Se+0.83- atom.