DOE OSTI2020
BiTeO3I crystallizes in the tetragonal P4/nmm space group. The structure is two-dimensional and consists of one BiOI sheet oriented in the (0, 0, 1) direction and two BiTe2O5I sheets oriented in the (0, 0, 1) direction. In the BiOI sheet, Bi3+ is bonded in a 4-coordinate geometry to four equivalent O2- and four equivalent I1- atoms. All Bi–O bond lengths are 2.35 Å. All Bi–I bond lengths are 3.39 Å. O2- is bonded to four equivalent Bi3+ atoms to form a mixture of edge and corner-sharing OBi4 tetrahedra. I1- is bonded in a 4-coordinate geometry to four equivalent Bi3+ atoms. In each BiTe2O5I sheet, Bi3+ is bonded to twelve O2- atoms to form distorted BiO12 cuboctahedra that share corners with four equivalent BiO12 cuboctahedra, faces with four equivalent BiO12 cuboctahedra, and faces with four equivalent TeO5 square pyramids. There are a spread of Bi–O bond distances ranging from 2.56–2.83 Å. There are two inequivalent Te4+ sites. In the first Te4+ site, Te4+ is bonded to five O2- atoms to form distorted TeO5 square pyramids that share corners with four equivalent TeO5 square pyramids and faces with four equivalent BiO12 cuboctahedra. There are one shorter (2.00 Å) and four longer (2.04 Å) Te–O bond lengths. In the second Te4+ site, Te4+ is bonded in a 4-coordinate geometry to four equivalent O2- and four equivalent I1- atoms. All Te–O bond lengths are 2.18 Å. All Te–I bond lengths are 3.47 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to four equivalent Bi3+ and one Te4+ atom. In the second O2- site, O2- is bonded to two equivalent Bi3+, two equivalent Te4+, and two equivalent I1- atoms to form a mixture of distorted edge, face, and corner-sharing OBi2Te2I2 tetrahedra. Both O–I bond lengths are 3.53 Å. In the third O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Bi3+ and two equivalent Te4+ atoms. I1- is bonded in a 8-coordinate geometry to four equivalent Te4+ and four equivalent O2- atoms.