Bi2MgO4 crystallizes in the orthorhombic Pmmn space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form distorted MgO6 pentagonal pyramids that share edges with four equivalent Bi(2)O6 octahedra. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(3) atoms. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), and four equivalent O(3) atoms. In the second Bi site, Bi(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form BiO6 octahedra that share edges with two equivalent Bi(2)O6 octahedra and edges with two equivalent Mg(1)O6 pentagonal pyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Bi(1), and two equivalent Bi(2) atoms. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(2), one Bi(1), and two equivalent Bi(2) atoms. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Mg(1), one Mg(2), one Bi(2), and two equivalent Bi(1) atoms.
Bi2MgO4 crystallizes in the orthorhombic Pmmn space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form distorted MgO6 pentagonal pyramids that share edges with four equivalent Bi(2)O6 octahedra. Both Mg(1)-O(1) bond lengths are 2.02 Å. All Mg(1)-O(3) bond lengths are 2.40 Å. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(3) atoms. Both Mg(2)-O(2) bond lengths are 2.11 Å. All Mg(2)-O(3) bond lengths are 2.60 Å. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), and four equivalent O(3) atoms. The Bi(1)-O(1) bond length is 2.60 Å. The Bi(1)-O(2) bond length is 2.27 Å. There are two shorter (2.21 Å) and two longer (2.83 Å) Bi(1)-O(3) bond lengths. In the second Bi site, Bi(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form BiO6 octahedra that share edges with two equivalent Bi(2)O6 octahedra and edges with two equivalent Mg(1)O6 pentagonal pyramids. Both Bi(2)-O(1) bond lengths are 2.30 Å. Both Bi(2)-O(2) bond lengths are 2.57 Å. Both Bi(2)-O(3) bond lengths are 2.45 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Bi(1), and two equivalent Bi(2) atoms. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(2), one Bi(1), and two equivalent Bi(2) atoms. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Mg(1), one Mg(2), one Bi(2), and two equivalent Bi(1) atoms.