Materials Data on SrSm2Nb2O9 by Materials Project
SrSm2Nb2O9 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. Sr2+ is bonded in a 12-coordinate geometry to eight O2- atoms. There are a spread of Sr–O bond distances ranging from 2.48–2.83 Å. Sm3+ is bonded to six O2- atoms to form distorted SmO6 pentagonal pyramids that share corners with two equivalent NbO6 octahedra, corners with two equivalent SmO6 pentagonal pyramids, and edges with six equivalent SmO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 42–64°. There are a spread of Sm–O bond distances ranging from 2.27–2.50 Å. Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with five equivalent NbO6 octahedra and corners with two equivalent SmO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 19–29°. There are a spread of Nb–O bond distances ranging from 1.89–2.16 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Sr2+ and two equivalent Nb5+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Sr2+ and two equivalent Nb5+ atoms. In the third O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Sm3+ and one Nb5+ atom. In the fourth O2- site, O2- is bonded to four equivalent Sm3+ atoms to form a mixture of edge and corner-sharing OSm4 tetrahedra. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Sr2+ and two equivalent Nb5+ atoms.