DOE OSTI2020
Rb2Bi2O5 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are two inequivalent Rb1+ sites. In the first Rb1+ site, Rb1+ is bonded in a body-centered cubic geometry to eight equivalent O2- atoms. All Rb–O bond lengths are 3.02 Å. In the second Rb1+ site, Rb1+ is bonded to twelve O2- atoms to form RbO12 cuboctahedra that share corners with four equivalent RbO12 cuboctahedra, faces with four equivalent RbO12 cuboctahedra, and faces with eight equivalent BiO5 square pyramids. There are four shorter (3.09 Å) and eight longer (3.28 Å) Rb–O bond lengths. Bi4+ is bonded to five O2- atoms to form BiO5 square pyramids that share corners with five equivalent BiO5 square pyramids and faces with four equivalent RbO12 cuboctahedra. There are one shorter (2.12 Å) and four longer (2.21 Å) Bi–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 6-coordinate geometry to four Rb1+ and two equivalent Bi4+ atoms. In the second O2- site, O2- is bonded to four equivalent Rb1+ and two equivalent Bi4+ atoms to form a mixture of distorted edge and corner-sharing ORb4Bi2 octahedra. The corner-sharing octahedral tilt angles are 0°.