DOE OSTI2020
Pb3Te2(O3Br)2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a 4-coordinate geometry to four O2- and four Br1- atoms. There are two shorter (2.46 Å) and two longer (2.65 Å) Pb–O bond lengths. There are one shorter (3.34 Å) and three longer (3.39 Å) Pb–Br bond lengths. In the second Pb2+ site, Pb2+ is bonded in a 5-coordinate geometry to five O2- and three Br1- atoms. There are a spread of Pb–O bond distances ranging from 2.44–2.71 Å. All Pb–Br bond lengths are 3.45 Å. In the third Pb2+ site, Pb2+ is bonded in a 9-coordinate geometry to eight O2- and one Br1- atom. There are a spread of Pb–O bond distances ranging from 2.57–3.06 Å. The Pb–Br bond length is 3.40 Å. There are two inequivalent Te4+ sites. In the first Te4+ site, Te4+ is bonded to four O2- atoms to form distorted edge-sharing TeO4 trigonal pyramids. There are two shorter (1.96 Å) and two longer (2.09 Å) Te–O bond lengths. In the second Te4+ site, Te4+ is bonded in a 3-coordinate geometry to three O2- and one Br1- atom. There is one shorter (1.88 Å) and two longer (1.91 Å) Te–O bond length. The Te–Br bond length is 3.43 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Pb2+ and two equivalent Te4+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to three Pb2+ and one Te4+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three Pb2+ and one Te4+ atom. In the fourth O2- site, O2- is bonded to three Pb2+ and one Te4+ atom to form distorted edge-sharing OTePb3 tetrahedra. There are two inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a 5-coordinate geometry to four Pb2+ and one Te4+ atom. In the second Br1- site, Br1- is bonded in a 8-coordinate geometry to four Pb2+ atoms.