CaMg6NbO8 is alpha Po-derived structured and crystallizes in the tetragonal P4/mmm space group. Ca(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form CaO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with four equivalent Ca(1)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, edges with four equivalent Ca(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. In the second Mg site, Mg(2) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, edges with four equivalent Nb(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. In the third Mg site, Mg(3) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Mg(3)O6 octahedra, edges with two equivalent Ca(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. Nb(1) is bonded to two equivalent O(1) and four equivalent O(4) atoms to form NbO6 octahedra that share corners with two equivalent Ca(1)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, edges with four equivalent Mg(2)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), four equivalent Mg(3), and one Nb(1) atom to form OCaMg4Nb octahedra that share corners with six equivalent O(1)CaMg4Nb octahedra, edges with four equivalent O(3)Ca2Mg4 octahedra, edges with four equivalent O(4)Mg4Nb2 octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second O site, O(2) is bonded to one Mg(1), one Mg(2), and four equivalent Mg(3) atoms to form OMg6 octahedra that share corners with six equivalent O(2)Mg6 octahedra, edges with four equivalent O(3)Ca2Mg4 octahedra, edges with four equivalent O(1)CaMg4Nb octahedra, and edges with four equivalent O(4)Mg4Nb2 octahedra. The corner-sharing octahedra are not tilted. In the third O site, O(3) is bonded to two equivalent Ca(1), two equivalent Mg(1), and two equivalent Mg(3) atoms to form OCa2Mg4 octahedra that share corners with two equivalent O(4)Mg4Nb2 octahedra, corners with four equivalent O(3)Ca2Mg4 octahedra, edges with four equivalent O(3)Ca2Mg4 octahedra, edges with four equivalent O(1)CaMg4Nb octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded to two equivalent Mg(2), two equivalent Mg(3), and two equivalent Nb(1) atoms to form OMg4Nb2 octahedra that share corners with two equivalent O(3)Ca2Mg4 octahedra, corners with four equivalent O(4)Mg4Nb2 octahedra, edges with four equivalent O(1)CaMg4Nb octahedra, edges with four equivalent O(4)Mg4Nb2 octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedra are not tilted.
CaMg6NbO8 is alpha Po-derived structured and crystallizes in the tetragonal P4/mmm space group. Ca(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form CaO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with four equivalent Ca(1)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. Both Ca(1)-O(1) bond lengths are 2.24 Å. All Ca(1)-O(3) bond lengths are 2.21 Å. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, edges with four equivalent Ca(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. Both Mg(1)-O(2) bond lengths are 2.22 Å. All Mg(1)-O(3) bond lengths are 2.21 Å. In the second Mg site, Mg(2) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, edges with four equivalent Nb(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. Both Mg(2)-O(2) bond lengths are 2.21 Å. All Mg(2)-O(4) bond lengths are 2.21 Å. In the third Mg site, Mg(3) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Mg(3)O6 octahedra, edges with two equivalent Ca(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. The Mg(3)-O(3) bond length is 2.22 Å. The Mg(3)-O(4) bond length is 2.22 Å. Both Mg(3)-O(1) bond lengths are 2.21 Å. Both Mg(3)-O(2) bond lengths are 2.21 Å. Nb(1) is bonded to two equivalent O(1) and four equivalent O(4) atoms to form NbO6 octahedra that share corners with two equivalent Ca(1)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, edges with four equivalent Mg(2)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. Both Nb(1)-O(1) bond lengths are 2.19 Å. All Nb(1)-O(4) bond lengths are 2.21 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), four equivalent Mg(3), and one Nb(1) atom to form OCaMg4Nb octahedra that share corners with six equivalent O(1)CaMg4Nb octahedra, edges with four equivalent O(3)Ca2Mg4 octahedra, edges with four equivalent O(4)Mg4Nb2 octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second O site, O(2) is bonded to one Mg(1), one Mg(2), and four equivalent Mg(3) atoms to form OMg6 octahedra that share corners with six equivalent O(2)Mg6 octahedra, edges with four equivalent O(3)Ca2Mg4 octahedra, edges with four equivalent O(1)CaMg4Nb octahedra, and edges with four equivalent O(4)Mg4Nb2 octahedra. The corner-sharing octahedra are not tilted. In the third O site, O(3) is bonded to two equivalent Ca(1), two equivalent Mg(1), and two equivalent Mg(3) atoms to form OCa2Mg4 octahedra that share corners with two equivalent O(4)Mg4Nb2 octahedra, corners with four equivalent O(3)Ca2Mg4 octahedra, edges with four equivalent O(3)Ca2Mg4 octahedra, edges with four equivalent O(1)CaMg4Nb octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded to two equivalent Mg(2), two equivalent Mg(3), and two equivalent Nb(1) atoms to form OMg4Nb2 octahedra that share corners with two equivalent O(3)Ca2Mg4 octahedra, corners with four equivalent O(4)Mg4Nb2 octahedra, edges with four equivalent O(1)CaMg4Nb octahedra, edges with four equivalent O(4)Mg4Nb2 octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedra are not tilted.