DOE OSTI2020
Ba2Ca4(CuO2)5Cu crystallizes in the tetragonal P4/mmm space group. The structure is two-dimensional and consists of one cuprum molecule and one Ba2Ca4(CuO2)5 sheet oriented in the (0, 0, 1) direction. In the Ba2Ca4(CuO2)5 sheet, Ba2+ is bonded in a 4-coordinate geometry to four equivalent O2- atoms. All Ba–O bond lengths are 2.61 Å. There are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are four shorter (2.52 Å) and four longer (2.56 Å) Ca–O bond lengths. In the second Ca2+ site, Ca2+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are four shorter (2.47 Å) and four longer (2.62 Å) Ca–O bond lengths. There are three inequivalent Cu+1.33+ sites. In the first Cu+1.33+ site, Cu+1.33+ is bonded in a rectangular see-saw-like geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.98 Å. In the second Cu+1.33+ site, Cu+1.33+ is bonded in a rectangular see-saw-like geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.97 Å. In the third Cu+1.33+ site, Cu+1.33+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.97 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Ba2+, two equivalent Ca2+, and two equivalent Cu+1.33+ atoms to form distorted OBa2Ca2Cu2 octahedra that share corners with eight OCa4Cu2 octahedra, edges with three OCa4Cu2 octahedra, and faces with four equivalent OBa2Ca2Cu2 octahedra. The corner-sharing octahedra tilt angles range from 4–67°. In the second O2- site, O2- is bonded to four Ca2+ and two equivalent Cu+1.33+ atoms to form a mixture of face, edge, and corner-sharing OCa4Cu2 octahedra. The corner-sharing octahedra tilt angles range from 1–67°. In the third O2- site, O2- is bonded to four equivalent Ca2+ and two equivalent Cu+1.33+ atoms to form a mixture of face, edge, and corner-sharing OCa4Cu2 octahedra. The corner-sharing octahedra tilt angles range from 0–67°.