DOE OSTI2020
Rb2CuBr3 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Rb1+ sites. In the first Rb1+ site, Rb1+ is bonded to seven Br1- atoms to form distorted RbBr7 pentagonal bipyramids that share corners with six RbBr7 pentagonal bipyramids, a cornercorner with one CuBr4 tetrahedra, edges with ten RbBr7 pentagonal bipyramids, and edges with four equivalent CuBr4 tetrahedra. There are a spread of Rb–Br bond distances ranging from 3.45–3.57 Å. In the second Rb1+ site, Rb1+ is bonded to seven Br1- atoms to form distorted RbBr7 pentagonal bipyramids that share corners with four equivalent RbBr7 pentagonal bipyramids, corners with three equivalent CuBr4 tetrahedra, edges with eight RbBr7 pentagonal bipyramids, edges with three equivalent CuBr4 tetrahedra, and faces with two equivalent RbBr7 pentagonal bipyramids. There are a spread of Rb–Br bond distances ranging from 3.48–3.59 Å. Cu1+ is bonded to four Br1- atoms to form CuBr4 tetrahedra that share corners with four RbBr7 pentagonal bipyramids, corners with two equivalent CuBr4 tetrahedra, and edges with seven RbBr7 pentagonal bipyramids. There are a spread of Cu–Br bond distances ranging from 2.46–2.58 Å. There are three inequivalent Br1- sites. In the first Br1- site, Br1- is bonded to four Rb1+ and two equivalent Cu1+ atoms to form a mixture of distorted edge and corner-sharing BrRb4Cu2 octahedra. The corner-sharing octahedra tilt angles range from 14–34°. In the second Br1- site, Br1- is bonded to five Rb1+ and one Cu1+ atom to form a mixture of distorted edge and corner-sharing BrRb5Cu octahedra. The corner-sharing octahedral tilt angles are 14°. In the third Br1- site, Br1- is bonded in a 6-coordinate geometry to five Rb1+ and one Cu1+ atom.