DOE OSTI2020
Ta2Tl4Se11 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to seven Se+1.27- atoms to form distorted face-sharing TaSe7 pentagonal bipyramids. There are a spread of Ta–Se bond distances ranging from 2.45–2.87 Å. In the second Ta5+ site, Ta5+ is bonded to seven Se+1.27- atoms to form distorted face-sharing TaSe7 pentagonal bipyramids. There are a spread of Ta–Se bond distances ranging from 2.47–2.85 Å. There are four inequivalent Tl1+ sites. In the first Tl1+ site, Tl1+ is bonded in a 9-coordinate geometry to nine Se+1.27- atoms. There are a spread of Tl–Se bond distances ranging from 3.09–3.89 Å. In the second Tl1+ site, Tl1+ is bonded in a 7-coordinate geometry to six Se+1.27- atoms. There are a spread of Tl–Se bond distances ranging from 3.16–3.54 Å. In the third Tl1+ site, Tl1+ is bonded in a 4-coordinate geometry to four Se+1.27- atoms. There are a spread of Tl–Se bond distances ranging from 3.22–3.37 Å. In the fourth Tl1+ site, Tl1+ is bonded in a 7-coordinate geometry to seven Se+1.27- atoms. There are a spread of Tl–Se bond distances ranging from 3.10–3.73 Å. There are eleven inequivalent Se+1.27- sites. In the first Se+1.27- site, Se+1.27- is bonded in a 5-coordinate geometry to one Ta5+ and four Tl1+ atoms. In the second Se+1.27- site, Se+1.27- is bonded in a 1-coordinate geometry to one Ta5+ and four Tl1+ atoms. In the third Se+1.27- site, Se+1.27- is bonded in a 1-coordinate geometry to one Ta5+ and two Tl1+ atoms. In the fourth Se+1.27- site, Se+1.27- is bonded in a 2-coordinate geometry to two Ta5+ and two equivalent Tl1+ atoms. In the fifth Se+1.27- site, Se+1.27- is bonded in a 4-coordinate geometry to two Ta5+ and two Tl1+ atoms. In the sixth Se+1.27- site, Se+1.27- is bonded in a 5-coordinate geometry to one Ta5+, three Tl1+, and one Se+1.27- atom. The Se–Se bond length is 2.40 Å. In the seventh Se+1.27- site, Se+1.27- is bonded in a distorted single-bond geometry to one Ta5+ and one Se+1.27- atom. In the eighth Se+1.27- site, Se+1.27- is bonded in a 1-coordinate geometry to one Ta5+, two equivalent Tl1+, and one Se+1.27- atom. The Se–Se bond length is 2.41 Å. In the ninth Se+1.27- site, Se+1.27- is bonded in a distorted single-bond geometry to one Ta5+ and three Tl1+ atoms. In the tenth Se+1.27- site, Se+1.27- is bonded in a 1-coordinate geometry to one Ta5+ and two Tl1+ atoms. In the eleventh Se+1.27- site, Se+1.27- is bonded in a 5-coordinate geometry to two Ta5+, two equivalent Tl1+, and one Se+1.27- atom.