DOE OSTI2020
RbNbGeO5 crystallizes in the orthorhombic P2_12_12_1 space group. The structure is three-dimensional. there are three inequivalent Rb1+ sites. In the first Rb1+ site, Rb1+ is bonded in a 3-coordinate geometry to three O2- atoms. There are a spread of Rb–O bond distances ranging from 3.00–3.07 Å. In the second Rb1+ site, Rb1+ is bonded in a 6-coordinate geometry to nine O2- atoms. There are a spread of Rb–O bond distances ranging from 3.10–3.53 Å. In the third Rb1+ site, Rb1+ is bonded in a 5-coordinate geometry to ten O2- atoms. There are a spread of Rb–O bond distances ranging from 3.09–3.57 Å. There are three inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with three NbO6 octahedra and corners with three GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 38–40°. There are a spread of Nb–O bond distances ranging from 1.93–2.09 Å. In the second Nb5+ site, Nb5+ is bonded to six O2- atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 38–42°. There are a spread of Nb–O bond distances ranging from 1.90–2.13 Å. In the third Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with three NbO6 octahedra and corners with three GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 40–42°. There are a spread of Nb–O bond distances ranging from 1.91–2.16 Å. There are three inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with two NbO6 octahedra and corners with two GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 41–43°. There is two shorter (1.74 Å) and two longer (1.79 Å) Ge–O bond length. In the second Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with two NbO6 octahedra and corners with two GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 13–55°. There are a spread of Ge–O bond distances ranging from 1.73–1.80 Å. In the third Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with two NbO6 octahedra and corners with two GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 40–44°. There are a spread of Ge–O bond distances ranging from 1.73–1.80 Å. There are fifteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to three Rb1+ and two Nb5+ atoms. In the second O2- site, O2- is bonded in a distorted linear geometry to one Nb5+ and one Ge4+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Rb1+, one Nb5+, and one Ge4+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Rb1+ and two Ge4+ atoms. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Rb1+, one Nb5+, and one Ge4+ atom. In the sixth O2- site, O2- is bonded in a bent 120 degrees geometry to one Rb1+ and two Ge4+ atoms. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Rb1+ and two equivalent Nb5+ atoms. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Rb1+ and two Nb5+ atoms. In the ninth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Rb1+ and two Nb5+ atoms. In the tenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Rb1+ and two Nb5+ atoms. In the eleventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Rb1+ and two Ge4+ atoms. In the twelfth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Rb1+, one Nb5+, and one Ge4+ atom. In the thirteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Rb1+, one Nb5+, and one Ge4+ atom. In the fourteenth O2- site, O2- is bonded in a 2-coordinate geometry to one Rb1+, one Nb5+, and one Ge4+ atom. In the fifteenth O2- site, O2- is bonded in a 2-coordinate geometry to two Rb1+ and two Nb5+ atoms.