Ba2MgNb4O12 crystallizes in the monoclinic Pm space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 8-coordinate geometry to one O(4), one O(7), two equivalent O(10), two equivalent O(11), and two equivalent O(9) atoms. In the second Ba site, Ba(2) is bonded in a 8-coordinate geometry to one O(4), one O(7), two equivalent O(3), two equivalent O(8), and two equivalent O(9) atoms. Mg(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(6), and two equivalent O(12) atoms. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(3), one O(8), one O(9), and two equivalent O(4) atoms to form a mixture of corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-42°. In the second Nb site, Nb(2) is bonded to one O(12), one O(2), one O(5), one O(8), and two equivalent O(1) atoms to form a mixture of distorted corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-42°. In the third Nb site, Nb(3) is bonded to one O(11), one O(12), one O(2), one O(5), and two equivalent O(6) atoms to form a mixture of distorted corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-44°. In the fourth Nb site, Nb(4) is bonded to one O(10), one O(11), one O(3), one O(9), and two equivalent O(7) atoms to form a mixture of corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-44°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a T-shaped geometry to one Mg(1) and two equivalent Nb(2) atoms. In the second O site, O(2) is bonded in a water-like geometry to one Nb(2) and one Nb(3) atom. In the third O site, O(3) is bonded to two equivalent Ba(2), one Nb(1), and one Nb(4) atom to form a mixture of distorted corner and edge-sharing OBa2Nb2 trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted linear geometry to one Ba(1), one Ba(2), and two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a water-like geometry to one Nb(2) and one Nb(3) atom. In the sixth O site, O(6) is bonded in a T-shaped geometry to one Mg(1) and two equivalent Nb(3) atoms. In the seventh O site, O(7) is bonded in a distorted linear geometry to one Ba(1), one Ba(2), and two equivalent Nb(4) atoms. In the eighth O site, O(8) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ba(2), one Nb(1), and one Nb(2) atom. In the ninth O site, O(9) is bonded in a distorted linear geometry to two equivalent Ba(1), two equivalent Ba(2), one Nb(1), and one Nb(4) atom. In the tenth O site, O(10) is bonded to two equivalent Ba(1), one Nb(1), and one Nb(4) atom to form a mixture of distorted corner and edge-sharing OBa2Nb2 trigonal pyramids. In the eleventh O site, O(11) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ba(1), one Nb(3), and one Nb(4) atom. In the twelfth O site, O(12) is bonded in a square co-planar geometry to two equivalent Mg(1), one Nb(2), and one Nb(3) atom.
Ba2MgNb4O12 crystallizes in the monoclinic Pm space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 8-coordinate geometry to one O(4), one O(7), two equivalent O(10), two equivalent O(11), and two equivalent O(9) atoms. The Ba(1)-O(4) bond length is 2.86 Å. The Ba(1)-O(7) bond length is 2.90 Å. Both Ba(1)-O(10) bond lengths are 2.67 Å. Both Ba(1)-O(11) bond lengths are 2.95 Å. Both Ba(1)-O(9) bond lengths are 2.96 Å. In the second Ba site, Ba(2) is bonded in a 8-coordinate geometry to one O(4), one O(7), two equivalent O(3), two equivalent O(8), and two equivalent O(9) atoms. The Ba(2)-O(4) bond length is 2.89 Å. The Ba(2)-O(7) bond length is 2.85 Å. Both Ba(2)-O(3) bond lengths are 2.67 Å. Both Ba(2)-O(8) bond lengths are 2.98 Å. Both Ba(2)-O(9) bond lengths are 2.94 Å. Mg(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(6), and two equivalent O(12) atoms. The Mg(1)-O(1) bond length is 1.93 Å. The Mg(1)-O(6) bond length is 1.93 Å. Both Mg(1)-O(12) bond lengths are 2.03 Å. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(3), one O(8), one O(9), and two equivalent O(4) atoms to form a mixture of corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-42°. The Nb(1)-O(10) bond length is 2.19 Å. The Nb(1)-O(3) bond length is 1.98 Å. The Nb(1)-O(8) bond length is 2.00 Å. The Nb(1)-O(9) bond length is 2.06 Å. Both Nb(1)-O(4) bond lengths are 2.03 Å. In the second Nb site, Nb(2) is bonded to one O(12), one O(2), one O(5), one O(8), and two equivalent O(1) atoms to form a mixture of distorted corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-42°. The Nb(2)-O(12) bond length is 2.21 Å. The Nb(2)-O(2) bond length is 1.86 Å. The Nb(2)-O(5) bond length is 2.25 Å. The Nb(2)-O(8) bond length is 2.00 Å. Both Nb(2)-O(1) bond lengths are 2.05 Å. In the third Nb site, Nb(3) is bonded to one O(11), one O(12), one O(2), one O(5), and two equivalent O(6) atoms to form a mixture of distorted corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-44°. The Nb(3)-O(11) bond length is 2.01 Å. The Nb(3)-O(12) bond length is 2.23 Å. The Nb(3)-O(2) bond length is 2.22 Å. The Nb(3)-O(5) bond length is 1.86 Å. Both Nb(3)-O(6) bond lengths are 2.06 Å. In the fourth Nb site, Nb(4) is bonded to one O(10), one O(11), one O(3), one O(9), and two equivalent O(7) atoms to form a mixture of corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-44°. The Nb(4)-O(10) bond length is 1.98 Å. The Nb(4)-O(11) bond length is 2.00 Å. The Nb(4)-O(3) bond length is 2.19 Å. The Nb(4)-O(9) bond length is 2.06 Å. Both Nb(4)-O(7) bond lengths are 2.03 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a T-shaped geometry to one Mg(1) and two equivalent Nb(2) atoms. In the second O site, O(2) is bonded in a water-like geometry to one Nb(2) and one Nb(3) atom. In the third O site, O(3) is bonded to two equivalent Ba(2), one Nb(1), and one Nb(4) atom to form a mixture of distorted corner and edge-sharing OBa2Nb2 trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted linear geometry to one Ba(1), one Ba(2), and two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a water-like geometry to one Nb(2) and one Nb(3) atom. In the sixth O site, O(6) is bonded in a T-shaped geometry to one Mg(1) and two equivalent Nb(3) atoms. In the seventh O site, O(7) is bonded in a distorted linear geometry to one Ba(1), one Ba(2), and two equivalent Nb(4) atoms. In the eighth O site, O(8) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ba(2), one Nb(1), and one Nb(2) atom. In the ninth O site, O(9) is bonded in a distorted linear geometry to two equivalent Ba(1), two equivalent Ba(2), one Nb(1), and one Nb(4) atom. In the tenth O site, O(10) is bonded to two equivalent Ba(1), one Nb(1), and one Nb(4) atom to form a mixture of distorted corner and edge-sharing OBa2Nb2 trigonal pyramids. In the eleventh O site, O(11) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ba(1), one Nb(3), and one Nb(4) atom. In the twelfth O site, O(12) is bonded in a square co-planar geometry to two equivalent Mg(1), one Nb(2), and one Nb(3) atom.