Sr3(MgTa2)O9 is (Cubic) Perovskite-derived structured and crystallizes in the trigonal P-3m1 space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form SrO12 cuboctahedra that share corners with six equivalent Sr(1)O12 cuboctahedra, corners with six equivalent Sr(2)O12 cuboctahedra, faces with six equivalent Sr(2)O12 cuboctahedra, faces with two equivalent Mg(1)O6 octahedra, and faces with six equivalent Ta(1)O6 octahedra. In the second Sr site, Sr(2) is bonded to three equivalent O(1) and nine equivalent O(2) atoms to form SrO12 cuboctahedra that share corners with three equivalent Sr(1)O12 cuboctahedra, corners with nine equivalent Sr(2)O12 cuboctahedra, faces with three equivalent Sr(1)O12 cuboctahedra, faces with three equivalent Sr(2)O12 cuboctahedra, faces with three equivalent Mg(1)O6 octahedra, and faces with five equivalent Ta(1)O6 octahedra. Mg(1) is bonded to six equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Ta(1)O6 octahedra, faces with two equivalent Sr(1)O12 cuboctahedra, and faces with six equivalent Sr(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 4°. Ta(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form TaO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with three equivalent Ta(1)O6 octahedra, faces with three equivalent Sr(1)O12 cuboctahedra, and faces with five equivalent Sr(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-4°. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Ta(1) atoms to form a mixture of distorted face and corner-sharing OSr4Ta2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. In the second O site, O(2) is bonded in a distorted linear geometry to one Sr(1), three equivalent Sr(2), one Mg(1), and one Ta(1) atom.
Sr3(MgTa2)O9 is (Cubic) Perovskite-derived structured and crystallizes in the trigonal P-3m1 space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form SrO12 cuboctahedra that share corners with six equivalent Sr(1)O12 cuboctahedra, corners with six equivalent Sr(2)O12 cuboctahedra, faces with six equivalent Sr(2)O12 cuboctahedra, faces with two equivalent Mg(1)O6 octahedra, and faces with six equivalent Ta(1)O6 octahedra. All Sr(1)-O(1) bond lengths are 2.86 Å. All Sr(1)-O(2) bond lengths are 2.84 Å. In the second Sr site, Sr(2) is bonded to three equivalent O(1) and nine equivalent O(2) atoms to form SrO12 cuboctahedra that share corners with three equivalent Sr(1)O12 cuboctahedra, corners with nine equivalent Sr(2)O12 cuboctahedra, faces with three equivalent Sr(1)O12 cuboctahedra, faces with three equivalent Sr(2)O12 cuboctahedra, faces with three equivalent Mg(1)O6 octahedra, and faces with five equivalent Ta(1)O6 octahedra. All Sr(2)-O(1) bond lengths are 2.83 Å. There are six shorter (2.86 Å) and three longer (2.93 Å) Sr(2)-O(2) bond lengths. Mg(1) is bonded to six equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Ta(1)O6 octahedra, faces with two equivalent Sr(1)O12 cuboctahedra, and faces with six equivalent Sr(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 4°. All Mg(1)-O(2) bond lengths are 2.07 Å. Ta(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form TaO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with three equivalent Ta(1)O6 octahedra, faces with three equivalent Sr(1)O12 cuboctahedra, and faces with five equivalent Sr(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-4°. All Ta(1)-O(1) bond lengths are 2.09 Å. All Ta(1)-O(2) bond lengths are 1.93 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Ta(1) atoms to form a mixture of distorted face and corner-sharing OSr4Ta2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. In the second O site, O(2) is bonded in a distorted linear geometry to one Sr(1), three equivalent Sr(2), one Mg(1), and one Ta(1) atom.