Mg2Ge2O5 crystallizes in the tetragonal P4/mmm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. In the second Mg site, Mg(2) is bonded to four equivalent O(2) and eight equivalent O(1) atoms to form distorted MgO12 cuboctahedra that share corners with four equivalent Mg(2)O12 cuboctahedra, faces with four equivalent Mg(2)O12 cuboctahedra, and faces with eight equivalent Ge(1)O5 square pyramids. Ge(1) is bonded to one O(2) and four equivalent O(1) atoms to form GeO5 square pyramids that share corners with five equivalent Ge(1)O5 square pyramids and faces with four equivalent Mg(2)O12 cuboctahedra. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), and two equivalent Ge(1) atoms to form a mixture of distorted edge, corner, and face-sharing OMg4Ge2 octahedra. The corner-sharing octahedral tilt angles range from 0-70°. In the second O site, O(2) is bonded in a linear geometry to four equivalent Mg(2) and two equivalent Ge(1) atoms.
Mg2Ge2O5 crystallizes in the tetragonal P4/mmm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. All Mg(1)-O(1) bond lengths are 2.39 Å. In the second Mg site, Mg(2) is bonded to four equivalent O(2) and eight equivalent O(1) atoms to form distorted MgO12 cuboctahedra that share corners with four equivalent Mg(2)O12 cuboctahedra, faces with four equivalent Mg(2)O12 cuboctahedra, and faces with eight equivalent Ge(1)O5 square pyramids. All Mg(2)-O(2) bond lengths are 2.74 Å. All Mg(2)-O(1) bond lengths are 2.61 Å. Ge(1) is bonded to one O(2) and four equivalent O(1) atoms to form GeO5 square pyramids that share corners with five equivalent Ge(1)O5 square pyramids and faces with four equivalent Mg(2)O12 cuboctahedra. The Ge(1)-O(2) bond length is 1.86 Å. All Ge(1)-O(1) bond lengths are 1.94 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), and two equivalent Ge(1) atoms to form a mixture of distorted edge, corner, and face-sharing OMg4Ge2 octahedra. The corner-sharing octahedral tilt angles range from 0-70°. In the second O site, O(2) is bonded in a linear geometry to four equivalent Mg(2) and two equivalent Ge(1) atoms.