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 12-coordinate geometry to one O(6), one O(7), two equivalent O(10), two equivalent O(11), two equivalent O(12), two equivalent O(5), and two equivalent O(9) atoms. In the second Ba site, Ba(2) is bonded in a 4-coordinate geometry to two equivalent O(2) and two equivalent O(3) atoms. Mg(1) is bonded in a see-saw-like geometry to one O(1), one O(4), and two equivalent O(8) 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 distorted edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 2-44°. 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 edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 2-44°. 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 edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 2-34°. 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 edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 2-34°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Mg(1) and two equivalent Nb(2) atoms. In the second O site, O(2) is bonded to two equivalent Ba(2), one Nb(2), and one Nb(3) atom to form a mixture of edge and corner-sharing OBa2Nb2 tetrahedra. 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 edge and corner-sharing OBa2Nb2 tetrahedra. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Mg(1) and two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Nb(2), and one Nb(3) atom. In the sixth O site, O(6) is bonded in a linear geometry to one Ba(1) and two equivalent Nb(3) atoms. In the seventh O site, O(7) is bonded in a linear geometry to one Ba(1) and two equivalent Nb(4) atoms. In the eighth O site, O(8) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(1), one Nb(1), and one Nb(2) atom. In the ninth O site, O(9) is bonded in a linear geometry to two equivalent Ba(1), one Nb(1), and one Nb(4) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Nb(1), and one Nb(4) atom. In the eleventh O site, O(11) is bonded in a distorted bent 150 degrees 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 linear geometry to two equivalent Ba(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 12-coordinate geometry to one O(6), one O(7), two equivalent O(10), two equivalent O(11), two equivalent O(12), two equivalent O(5), and two equivalent O(9) atoms. The Ba(1)-O(6) bond length is 3.38 Å. The Ba(1)-O(7) bond length is 3.37 Å. Both Ba(1)-O(10) bond lengths are 2.99 Å. Both Ba(1)-O(11) bond lengths are 2.91 Å. Both Ba(1)-O(12) bond lengths are 3.32 Å. Both Ba(1)-O(5) bond lengths are 2.97 Å. Both Ba(1)-O(9) bond lengths are 3.34 Å. In the second Ba site, Ba(2) is bonded in a 4-coordinate geometry to two equivalent O(2) and two equivalent O(3) atoms. Both Ba(2)-O(2) bond lengths are 2.61 Å. Both Ba(2)-O(3) bond lengths are 2.61 Å. Mg(1) is bonded in a see-saw-like geometry to one O(1), one O(4), and two equivalent O(8) atoms. The Mg(1)-O(1) bond length is 1.94 Å. The Mg(1)-O(4) bond length is 1.94 Å. Both Mg(1)-O(8) bond lengths are 2.00 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 distorted edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 2-44°. The Nb(1)-O(10) bond length is 1.89 Å. The Nb(1)-O(3) bond length is 2.09 Å. The Nb(1)-O(8) bond length is 2.39 Å. The Nb(1)-O(9) bond length is 1.99 Å. Both Nb(1)-O(4) bond lengths are 2.05 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 edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 2-44°. The Nb(2)-O(12) bond length is 1.98 Å. The Nb(2)-O(2) bond length is 2.10 Å. The Nb(2)-O(5) bond length is 1.90 Å. The Nb(2)-O(8) bond length is 2.41 Å. Both Nb(2)-O(1) bond lengths are 2.04 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 edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 2-34°. The Nb(3)-O(11) bond length is 2.03 Å. The Nb(3)-O(12) bond length is 1.96 Å. The Nb(3)-O(2) bond length is 2.10 Å. The Nb(3)-O(5) bond length is 2.27 Å. Both Nb(3)-O(6) bond lengths are 2.00 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 edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 2-34°. The Nb(4)-O(10) bond length is 2.28 Å. The Nb(4)-O(11) bond length is 2.00 Å. The Nb(4)-O(3) bond length is 2.10 Å. The Nb(4)-O(9) bond length is 1.96 Å. Both Nb(4)-O(7) bond lengths are 2.00 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Mg(1) and two equivalent Nb(2) atoms. In the second O site, O(2) is bonded to two equivalent Ba(2), one Nb(2), and one Nb(3) atom to form a mixture of edge and corner-sharing OBa2Nb2 tetrahedra. 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 edge and corner-sharing OBa2Nb2 tetrahedra. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Mg(1) and two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Nb(2), and one Nb(3) atom. In the sixth O site, O(6) is bonded in a linear geometry to one Ba(1) and two equivalent Nb(3) atoms. In the seventh O site, O(7) is bonded in a linear geometry to one Ba(1) and two equivalent Nb(4) atoms. In the eighth O site, O(8) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(1), one Nb(1), and one Nb(2) atom. In the ninth O site, O(9) is bonded in a linear geometry to two equivalent Ba(1), one Nb(1), and one Nb(4) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Nb(1), and one Nb(4) atom. In the eleventh O site, O(11) is bonded in a distorted bent 150 degrees 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 linear geometry to two equivalent Ba(1), one Nb(2), and one Nb(3) atom.