Materials Data on Rb3Nb2Br9 by Materials Project
Rb3Nb2Br9 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Rb1+ sites. In the first Rb1+ site, Rb1+ is bonded to twelve Br1- atoms to form RbBr12 cuboctahedra that share corners with twelve RbBr12 cuboctahedra, faces with six equivalent RbBr12 cuboctahedra, and faces with six equivalent NbBr6 octahedra. There are six shorter (3.71 Å) and six longer (3.93 Å) Rb–Br bond lengths. In the second Rb1+ site, Rb1+ is bonded to twelve Br1- atoms to form RbBr12 cuboctahedra that share corners with nine RbBr12 cuboctahedra, corners with three equivalent NbBr6 octahedra, faces with seven RbBr12 cuboctahedra, and faces with four equivalent NbBr6 octahedra. The corner-sharing octahedral tilt angles are 26°. There are a spread of Rb–Br bond distances ranging from 3.65–4.01 Å. Nb3+ is bonded to six Br1- atoms to form NbBr6 octahedra that share corners with three equivalent RbBr12 cuboctahedra, faces with seven RbBr12 cuboctahedra, and a faceface with one NbBr6 octahedra. There are three shorter (2.63 Å) and three longer (2.70 Å) Nb–Br bond lengths. There are two inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a distorted single-bond geometry to four Rb1+ and one Nb3+ atom. In the second Br1- site, Br1- is bonded in a 6-coordinate geometry to four Rb1+ and two equivalent Nb3+ atoms.