DOE OSTI2020
Na7Au5S6 crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. there are four inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to four equivalent Au1+ and four S2- atoms to form NaAu4S4 hexagonal bipyramids that share corners with four equivalent NaAu4S4 hexagonal bipyramids, edges with two equivalent NaAu3S4 pentagonal bipyramids, and faces with two equivalent NaAu3S4 pentagonal bipyramids. There are two shorter (3.18 Å) and two longer (3.23 Å) Na–Au bond lengths. There are two shorter (2.87 Å) and two longer (2.95 Å) Na–S bond lengths. In the second Na1+ site, Na1+ is bonded in a 6-coordinate geometry to two Au1+ and four S2- atoms. There are one shorter (3.27 Å) and one longer (3.32 Å) Na–Au bond lengths. There are a spread of Na–S bond distances ranging from 2.80–2.97 Å. In the third Na1+ site, Na1+ is bonded to three Au1+ and four S2- atoms to form distorted NaAu3S4 pentagonal bipyramids that share corners with two equivalent SNa6Au pentagonal bipyramids, corners with three equivalent NaAu3S4 pentagonal bipyramids, an edgeedge with one NaAu4S4 hexagonal bipyramid, and a faceface with one NaAu4S4 hexagonal bipyramid. There are one shorter (3.13 Å) and two longer (3.25 Å) Na–Au bond lengths. There are a spread of Na–S bond distances ranging from 2.84–2.90 Å. In the fourth Na1+ site, Na1+ is bonded in a 6-coordinate geometry to two Au1+ and four S2- atoms. There are one shorter (3.08 Å) and one longer (3.16 Å) Na–Au bond lengths. There are a spread of Na–S bond distances ranging from 2.89–2.98 Å. There are three inequivalent Au1+ sites. In the first Au1+ site, Au1+ is bonded in a 5-coordinate geometry to three Na1+ and two S2- atoms. Both Au–S bond lengths are 2.33 Å. In the second Au1+ site, Au1+ is bonded in a 5-coordinate geometry to three Na1+ and two S2- atoms. There are one shorter (2.33 Å) and one longer (2.34 Å) Au–S bond lengths. In the third Au1+ site, Au1+ is bonded in a distorted body-centered cubic geometry to six Na1+ and two equivalent S2- atoms. Both Au–S bond lengths are 2.34 Å. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded to six Na1+ and one Au1+ atom to form distorted SNa6Au pentagonal bipyramids that share corners with two equivalent NaAu3S4 pentagonal bipyramids, corners with three equivalent SNa6Au pentagonal bipyramids, and edges with three equivalent SNa6Au pentagonal bipyramids. In the second S2- site, S2- is bonded in a 6-coordinate geometry to four Na1+ and two Au1+ atoms. In the third S2- site, S2- is bonded in a 6-coordinate geometry to four Na1+ and two Au1+ atoms.