DOE OSTI2020
Sm7O18(Br)3 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional and consists of six hydrobromic acid molecules and one Sm7O18 framework. In the Sm7O18 framework, there are three inequivalent Sm3+ sites. In the first Sm3+ site, Sm3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Sm–O bond distances ranging from 2.33–2.46 Å. In the second Sm3+ site, Sm3+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Sm–O bond distances ranging from 2.41–2.76 Å. In the third Sm3+ site, Sm3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are three shorter (2.45 Å) and six longer (2.50 Å) Sm–O bond lengths. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to three equivalent Sm3+ and one O2- atom. The O–O bond length is 1.47 Å. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Sm3+ and one O2- atom. The O–O bond length is 1.49 Å. In the third O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three equivalent Sm3+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Sm3+ atoms. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to three Sm3+ and one O2- atom. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to four Sm3+ and one O2- atom.