Materials Data on RbCaMg6 by Materials Project
RbCaMg6 crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. Rb is bonded to two equivalent Ca and ten Mg atoms to form distorted RbCa2Mg10 cuboctahedra that share corners with four equivalent CaRb2Mg10 cuboctahedra, corners with six equivalent RbCa2Mg10 cuboctahedra, edges with two equivalent CaRb2Mg10 cuboctahedra, faces with two equivalent RbCa2Mg10 cuboctahedra, and faces with two equivalent CaRb2Mg10 cuboctahedra. Both Rb–Ca bond lengths are 3.82 Å. There are a spread of Rb–Mg bond distances ranging from 3.44–3.57 Å. Ca is bonded to two equivalent Rb and ten Mg atoms to form distorted CaRb2Mg10 cuboctahedra that share corners with four equivalent RbCa2Mg10 cuboctahedra, corners with six equivalent CaRb2Mg10 cuboctahedra, edges with two equivalent RbCa2Mg10 cuboctahedra, faces with two equivalent RbCa2Mg10 cuboctahedra, and faces with two equivalent CaRb2Mg10 cuboctahedra. There are a spread of Ca–Mg bond distances ranging from 3.43–3.53 Å. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a 10-coordinate geometry to two equivalent Rb, two equivalent Ca, and six Mg atoms. There are two shorter (3.31 Å) and four longer (3.43 Å) Mg–Mg bond lengths. In the second Mg site, Mg is bonded in a 8-coordinate geometry to two equivalent Rb, two equivalent Ca, and four Mg atoms. There are one shorter (3.10 Å) and one longer (3.31 Å) Mg–Mg bond lengths. In the third Mg site, Mg is bonded in a 2-coordinate geometry to two equivalent Ca and six Mg atoms. In the fourth Mg site, Mg is bonded in a 8-coordinate geometry to two equivalent Rb and six Mg atoms.