DOE OSTI2020
Bi5O7I crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are five inequivalent Bi3+ sites. In the first Bi3+ site, Bi3+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Bi–O bond distances ranging from 2.30–2.77 Å. In the second Bi3+ site, Bi3+ is bonded in a 4-coordinate geometry to four O2- and four equivalent I1- atoms. There are a spread of Bi–O bond distances ranging from 2.16–2.30 Å. There are two shorter (3.96 Å) and two longer (3.98 Å) Bi–I bond lengths. In the third Bi3+ site, Bi3+ is bonded in a 5-coordinate geometry to five O2- and two equivalent I1- atoms. There are a spread of Bi–O bond distances ranging from 2.15–2.95 Å. Both Bi–I bond lengths are 3.87 Å. In the fourth Bi3+ site, Bi3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Bi–O bond distances ranging from 2.14–2.77 Å. In the fifth Bi3+ site, Bi3+ is bonded in a 4-coordinate geometry to four O2- and two equivalent I1- atoms. There are a spread of Bi–O bond distances ranging from 2.11–2.28 Å. Both Bi–I bond lengths are 3.85 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded to four Bi3+ atoms to form a mixture of distorted edge and corner-sharing OBi4 tetrahedra. In the second O2- site, O2- is bonded in a 2-coordinate geometry to four Bi3+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to four Bi3+ atoms. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to four Bi3+ and two equivalent I1- atoms. There are one shorter (3.86 Å) and one longer (4.08 Å) O–I bond lengths. In the fifth O2- site, O2- is bonded to four Bi3+ atoms to form a mixture of distorted edge and corner-sharing OBi4 tetrahedra. In the sixth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Bi3+ and one I1- atom. The O–I bond length is 3.99 Å. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to four Bi3+ and one I1- atom. The O–I bond length is 4.00 Å. I1- is bonded in a 5-coordinate geometry to eight Bi3+, four O2-, and two equivalent I1- atoms. Both I–I bond lengths are 4.26 Å.