DOE OSTI2020
Ge9(Sb5Te12)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are nine inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded to six Te2- atoms to form distorted GeTe6 octahedra that share corners with five GeTe6 octahedra, edges with two equivalent GeTe6 octahedra, and edges with six SbTe6 octahedra. The corner-sharing octahedra tilt angles range from 10–14°. There are a spread of Ge–Te bond distances ranging from 2.80–3.42 Å. In the second Ge4+ site, Ge4+ is bonded in a 6-coordinate geometry to six Te2- atoms. There are a spread of Ge–Te bond distances ranging from 2.74–3.46 Å. In the third Ge4+ site, Ge4+ is bonded to six Te2- atoms to form GeTe6 octahedra that share corners with four equivalent GeTe6 octahedra, edges with six SbTe6 octahedra, and edges with four equivalent GeTe5 square pyramids. The corner-sharing octahedra tilt angles range from 6–7°. There are a spread of Ge–Te bond distances ranging from 2.88–3.33 Å. In the fourth Ge4+ site, Ge4+ is bonded to six Te2- atoms to form GeTe6 octahedra that share corners with five GeTe6 octahedra, edges with four equivalent GeTe6 octahedra, and edges with eight SbTe6 octahedra. The corner-sharing octahedra tilt angles range from 9–10°. There are a spread of Ge–Te bond distances ranging from 2.85–3.31 Å. In the fifth Ge4+ site, Ge4+ is bonded to six Te2- atoms to form distorted GeTe6 octahedra that share a cornercorner with one SbTe6 octahedra, corners with four equivalent GeTe6 octahedra, edges with two equivalent GeTe6 octahedra, and edges with four equivalent SbTe6 octahedra. The corner-sharing octahedra tilt angles range from 2–12°. There are a spread of Ge–Te bond distances ranging from 2.68–3.38 Å. In the sixth Ge4+ site, Ge4+ is bonded to six Te2- atoms to form distorted GeTe6 octahedra that share corners with five GeTe6 octahedra and edges with eight SbTe6 octahedra. The corner-sharing octahedra tilt angles range from 5–12°. There are a spread of Ge–Te bond distances ranging from 2.78–3.42 Å. In the seventh Ge4+ site, Ge4+ is bonded to five Te2- atoms to form distorted GeTe5 square pyramids that share corners with four SbTe6 octahedra, corners with four equivalent GeTe5 square pyramids, edges with two equivalent SbTe6 octahedra, and edges with four equivalent GeTe6 octahedra. The corner-sharing octahedra tilt angles range from 82–84°. There are a spread of Ge–Te bond distances ranging from 2.65–3.24 Å. In the eighth Ge4+ site, Ge4+ is bonded to six Te2- atoms to form distorted GeTe6 octahedra that share corners with six GeTe6 octahedra and edges with eight SbTe6 octahedra. The corner-sharing octahedra tilt angles range from 4–12°. There are a spread of Ge–Te bond distances ranging from 2.77–3.43 Å. In the ninth Ge4+ site, Ge4+ is bonded to six Te2- atoms to form GeTe6 octahedra that share corners with five GeTe6 octahedra, edges with four equivalent GeTe6 octahedra, and edges with eight SbTe6 octahedra. The corner-sharing octahedra tilt angles range from 7–9°. There are a spread of Ge–Te bond distances ranging from 2.85–3.36 Å. There are ten inequivalent Sb+1.20+ sites. In the first Sb+1.20+ site, Sb+1.20+ is bonded to six Te2- atoms to form SbTe6 octahedra that share corners with five SbTe6 octahedra, corners with two equivalent GeTe5 square pyramids, edges with four GeTe6 octahedra, and edges with four equivalent SbTe6 octahedra. The corner-sharing octahedra tilt angles range from 6–11°. There are a spread of Sb–Te bond distances ranging from 2.87–3.29 Å. In the second Sb+1.20+ site, Sb+1.20+ is bonded to six Te2- atoms to form distorted SbTe6 octahedra that share corners with six SbTe6 octahedra, edges with four GeTe6 octahedra, and edges with four equivalent SbTe6 octahedra. The corner-sharing octahedra tilt angles range from 6–19°. There are a spread of Sb–Te bond distances ranging from 2.81–3.40 Å. In the third Sb+1.20+ site, Sb+1.20+ is bonded to six Te2- atoms to form SbTe6 octahedra that share corners with six SbTe6 octahedra, edges with four equivalent SbTe6 octahedra, and edges with six GeTe6 octahedra. The corner-sharing octahedra tilt angles range from 4–16°. There are a spread of Sb–Te bond distances ranging from 2.82–3.37 Å. In the fourth Sb+1.20+ site, Sb+1.20+ is bonded to six Te2- atoms to form distorted SbTe6 octahedra that share a cornercorner with one GeTe6 octahedra, corners with five SbTe6 octahedra, edges with four equivalent SbTe6 octahedra, and edges with six GeTe6 octahedra. The corner-sharing octahedra tilt angles range from 2–15°. There are a spread of Sb–Te bond distances ranging from 2.79–3.45 Å. In the fifth Sb+1.20+ site, Sb+1.20+ is bonded to six Te2- atoms to form SbTe6 octahedra that share corners with six SbTe6 octahedra and edges with six GeTe6 octahedra. The corner-sharing octahedra tilt angles range from 7–12°. There are a spread of Sb–Te bond distances ranging from 2.86–3.34 Å. In the sixth Sb+1.20+ site, Sb+1.20+ is bonded to six Te2- atoms to form SbTe6 octahedra that share corners with six SbTe6 octahedra, corners with two equivalent GeTe5 square pyramids, edges with four GeTe6 octahedra, and edges with four equivalent SbTe6 octahedra. The corner-sharing octahedra tilt angles range from 6–10°. There are a spread of Sb–Te bond distances ranging from 2.93–3.19 Å. In the seventh Sb+1.20+ site, Sb+1.20+ is bonded to six Te2- atoms to form distorted SbTe6 octahedra that share corners with six SbTe6 octahedra, edges with two equivalent GeTe6 octahedra, and edges with two equivalent GeTe5 square pyramids. The corner-sharing octahedra tilt angles range from 10–19°. There are a spread of Sb–Te bond distances ranging from 2.82–3.44 Å. In the eighth Sb+1.20+ site, Sb+1.20+ is bonded to six Te2- atoms to form distorted SbTe6 octahedra that share corners with six SbTe6 octahedra, edges with four GeTe6 octahedra, and edges with four equivalent SbTe6 octahedra. The corner-sharing octahedra tilt angles range from 8–19°. There are a spread of Sb–Te bond distances ranging from 2.83–3.38 Å. In the ninth Sb+1.20+ site, Sb+1.20+ is bonded to six Te2- atoms to form distorted SbTe6 octahedra that share corners with six SbTe6 octahedra, edges with four equivalent SbTe6 octahedra, and edges with six GeTe6 octahedra. The corner-sharing octahedra tilt angles range from 4–18°. There are a spread of Sb–Te bond distances ranging from 2.78–3.52 Å. In the tenth Sb+1.20+ site, Sb+1.20+ is bonded to six Te2- atoms to form SbTe6 octahedra that share corners with six SbTe6 octahedra, edges with four equivalent SbTe6 octahedra, and edges with six GeTe6 octahedra. The corner-sharing octahedra tilt angles range from 2–7°. There are a spread of Sb–Te bond distances ranging from 3.03–3.15 Å. There are twenty-four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to one Ge4+ and four Sb+1.20+ atoms to form TeGeSb4 square pyramids that share a cornercorner with one TeGe2Sb4 octahedra, corners with four equivalent TeGeSb4 square pyramids, and edges with eight TeGe4Sb2 octahedra. The corner-sharing octahedral tilt angles are 7°. In the second Te2- site, Te2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ge4+ and two equivalent Sb+1.20+ atoms. In the third Te2- site, Te2- is bonded in a distorted T-shaped geometry to one Ge4+ and two equivalent Sb+1.20+ atoms. In the fourth Te2- site, Te2- is bonded to two Ge4+ and four Sb+1.20+ atoms to form TeGe2Sb4 octahedra that share corners with five TeGe2Sb4 octahedra and a cornercorner with one TeGeSb4 square pyramid. The corner-sharing octahedra tilt angles range from 11–15°. In the fifth Te2- site, Te2- is bonded to two Ge4+ and four Sb+1.20+ atoms to form TeGe2Sb4 octahedra that share corners with five TeGe4Sb2 octahedra, a cornercorner with one TeGeSb4 square pyramid, edges with four TeGe4Sb2 octahedra, and edges with four equivalent TeGeSb4 square pyramids. The corner-sharing octahedra tilt angles range from 2–12°. In the sixth Te2- site, Te2- is bonded to four Ge4+ and two equivalent Sb+1.20+ atoms to form corner-sharing TeGe4Sb2 octahedra. The corner-sharing octahedra tilt angles range from 11–12°. In the seventh Te2- site, Te2- is bonded to one Ge4+ and four Sb+1.20+ atoms to form TeGeSb4 square pyramids that share corners with four equivalent TeGeSb4 square pyramids, edges with two equivalent TeGe4Sb2 octahedra, and edges with six TeGeSb4 square pyramids. In the eighth Te2- site, Te2- is bonded in a distorted rectangular see-saw-like geometry to two Ge4+ and two equivalent Sb+1.20+ atoms. In the ninth Te2- site, Te2- is bonded in a distorted square co-planar geometry to four Sb+1.20+ atoms. In the tenth Te2- site, Te2- is bonded to one Ge4+ and four Sb+1.20+ atoms to form distorted TeGeSb4 square pyramids that share a cornercorner with one TeGe2Sb4 octahedra, corners with four equivalent TeGeSb4 square pyramids, and edges with eight TeGe4Sb2 octahedra. The corner-sharing octahedral tilt angles are 9°. In the eleventh Te2- site, Te2- is bonded in a distorted L-shaped geometry to three Ge4+ atoms. In the twelfth Te2- site, Te2- is bonded in a distorted rectangular see-saw-like geometry to three Ge4+ and one Sb+1.20+ atom. In the thirteenth Te2- site, Te2- is bonded to four Ge4+ and one Sb+1.20+ atom to form TeGe4Sb square pyramids that share corners with six TeGeSb4 square pyramids, edges with four equivalent TeGe4Sb2 octahedra, and edges with two equivalent TeGeSb4 square pyramids. In the fourteenth Te2- site, Te2- is bonded in a 4-coordinate geometry to two equivalent Ge4+ and two Sb+1.20+ atoms. In the fifteenth Te2- site, Te2- is bonded in a 2-coordinate geometry to two equivalent Ge4+ and two Sb+1.20+ atoms. In the sixteenth Te2- site, Te2- is bonded to four Ge4+ and two Sb+1.20+ atoms to form distorted TeGe4Sb2 octahedra that share corners with four equivalent TeGe4Sb2 octahedra, edges with eight TeGe4Sb2 octahedra, and edges with four TeGeSb4 square pyramids. The corner-sharing octahedra tilt angles range from 7–9°. In the seventeenth Te2- site, Te2- is bonded in a 4-coordinate geometry to two equivalent Ge4+ and two Sb+1.20+ atoms. In the eighteenth Te2- site, Te2- is bonded in a 3-coordinate geometry to two equivalent Ge4+ and two Sb+1.20+ atoms. In the nineteenth Te2- site, Te2- is bonded to four Ge4+ and two Sb+1.20+ atoms to form distorted TeGe4Sb2 octahedra that share corners with four equivalent TeGe4Sb2 octahedra, corners with two equivalent TeGeSb4 square pyramids, and edges with six TeGeSb4 square pyramids. The corner-sharing octahedra tilt angles range from 6–16°. In the twentieth Te2- site, Te2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ge4+ and two Sb+1.20+ atoms. In the twenty-first Te2- site, Te2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ge4+ and two Sb+1.20+ atoms. In the twenty-second Te2- site, Te2- is bonded to four Ge4+ and two Sb+1.20+ atoms to form distorted TeGe4Sb2 octahedra that share corners with four equivalent TeGe4Sb2 octahedra, edges with eight TeGe4Sb2 octahedra, and edges with four TeGeSb4 square pyramids. The corner-sharing octahedra tilt angles range from 8–9°. In the twenty-third Te2- site, Te2- is bonded to one Ge4+ and four Sb+1.20+ atoms to form distorted TeGeSb4 square pyramids that share corners with three TeGe4Sb2 octahedra, corners with six TeGeSb4 square pyramids, and edges with four equivalent TeGeSb4 square pyramids. The corner-sharing octahedra tilt angles range from 10–87°. In the twenty-fourth Te2- site, Te2- is bonded to two Ge4+ and four Sb+1.20+ atoms to form TeGe2Sb4 octahedra that share corners with five TeGe2Sb4 octahedra, a cornercorner with one TeGeSb4 square pyramid, edges with four TeGe4Sb2 octahedra, and edges with four equivalent TeGeSb4 square pyramids. The corner-sharing octahedra tilt angles range from 10–13°.