DOE OSTI2020
Na2Ba3Sb4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a distorted T-shaped geometry to five Sb2- atoms. There are a spread of Na–Sb bond distances ranging from 3.21–3.75 Å. In the second Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six Sb2- atoms. There are a spread of Na–Sb bond distances ranging from 3.39–3.60 Å. There are three inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded to seven Sb2- atoms to form a mixture of distorted corner, edge, and face-sharing BaSb7 pentagonal bipyramids. There are a spread of Ba–Sb bond distances ranging from 3.60–4.00 Å. In the second Ba2+ site, Ba2+ is bonded to seven Sb2- atoms to form a mixture of distorted corner, edge, and face-sharing BaSb7 pentagonal bipyramids. There are a spread of Ba–Sb bond distances ranging from 3.59–4.03 Å. In the third Ba2+ site, Ba2+ is bonded in a 6-coordinate geometry to six Sb2- atoms. There are a spread of Ba–Sb bond distances ranging from 3.41–3.60 Å. There are four inequivalent Sb2- sites. In the first Sb2- site, Sb2- is bonded in a 8-coordinate geometry to three Na1+, four Ba2+, and one Sb2- atom. The Sb–Sb bond length is 2.90 Å. In the second Sb2- site, Sb2- is bonded in a 9-coordinate geometry to three Na1+, five Ba2+, and one Sb2- atom. In the third Sb2- site, Sb2- is bonded in a 9-coordinate geometry to two Na1+, six Ba2+, and one Sb2- atom. The Sb–Sb bond length is 2.98 Å. In the fourth Sb2- site, Sb2- is bonded in a 9-coordinate geometry to three Na1+, five Ba2+, and one Sb2- atom. The Sb–Sb bond length is 2.91 Å.