MgHo4Ti2O10 crystallizes in the monoclinic Pm space group. Mg(1) is bonded in a distorted T-shaped geometry to one O(4) and two equivalent O(1) atoms. There are two inequivalent Ho sites. In the first Ho site, Ho(1) is bonded to one O(1), one O(3), one O(5), one O(6), and two equivalent O(2) atoms to form distorted HoO6 pentagonal pyramids that share  a cornercorner with one Ti(2)O6 octahedra, corners with three equivalent Ho(1)O6 pentagonal pyramids, edges with two equivalent Ti(2)O6 octahedra, and  an edgeedge with one Ti(1)O6 pentagonal pyramid. The corner-sharing octahedral tilt angles are 31°. In the second Ho site, Ho(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one O(6), and two equivalent O(5) atoms. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form distorted TiO6 pentagonal pyramids that share corners with two equivalent Ti(1)O6 pentagonal pyramids and edges with two equivalent Ho(1)O6 pentagonal pyramids. In the second Ti site, Ti(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(6) atoms to form distorted TiO6 octahedra that share corners with two equivalent Ti(2)O6 octahedra, corners with two equivalent Ho(1)O6 pentagonal pyramids, and edges with four equivalent Ho(1)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 31°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), one Ho(1), one Ho(2), and one Ti(1) atom. In the second O site, O(2) is bonded to one Ho(2), two equivalent Ho(1), and one Ti(2) atom to form OHo3Ti trigonal pyramids that share  a cornercorner with one O(4)Ho2MgTi2 trigonal bipyramid, corners with three equivalent O(2)Ho3Ti trigonal pyramids, edges with two equivalent O(3)Ho2Ti2 tetrahedra, and edges with two equivalent O(5)Ho3Ti tetrahedra. In the third O site, O(3) is bonded to two equivalent Ho(1) and two equivalent Ti(2) atoms to form distorted OHo2Ti2 tetrahedra that share corners with two equivalent O(3)Ho2Ti2 tetrahedra, corners with two equivalent O(5)Ho3Ti tetrahedra, and edges with four equivalent O(2)Ho3Ti trigonal pyramids. In the fourth O site, O(4) is bonded to one Mg(1), two equivalent Ho(2), and two equivalent Ti(1) atoms to form OHo2MgTi2 trigonal bipyramids that share corners with two equivalent O(4)Ho2MgTi2 trigonal bipyramids, corners with two equivalent O(2)Ho3Ti trigonal pyramids, and edges with four equivalent O(5)Ho3Ti tetrahedra. In the fifth O site, O(5) is bonded to one Ho(1), two equivalent Ho(2), and one Ti(1) atom to form OHo3Ti tetrahedra that share  a cornercorner with one O(3)Ho2Ti2 tetrahedra, corners with three equivalent O(5)Ho3Ti tetrahedra, edges with two equivalent O(4)Ho2MgTi2 trigonal bipyramids, and edges with two equivalent O(2)Ho3Ti trigonal pyramids. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Ho(1), one Ho(2), and one Ti(2) atom.
MgHo4Ti2O10 crystallizes in the monoclinic Pm space group. Mg(1) is bonded in a distorted T-shaped geometry to one O(4) and two equivalent O(1) atoms. The Mg(1)-O(4) bond length is 2.08 Å. Both Mg(1)-O(1) bond lengths are 2.09 Å. There are two inequivalent Ho sites. In the first Ho site, Ho(1) is bonded to one O(1), one O(3), one O(5), one O(6), and two equivalent O(2) atoms to form distorted HoO6 pentagonal pyramids that share  a cornercorner with one Ti(2)O6 octahedra, corners with three equivalent Ho(1)O6 pentagonal pyramids, edges with two equivalent Ti(2)O6 octahedra, and  an edgeedge with one Ti(1)O6 pentagonal pyramid. The corner-sharing octahedral tilt angles are 31°. The Ho(1)-O(1) bond length is 2.30 Å. The Ho(1)-O(3) bond length is 2.39 Å. The Ho(1)-O(5) bond length is 2.28 Å. The Ho(1)-O(6) bond length is 2.21 Å. There is one shorter (2.19 Å) and one longer (2.22 Å) Ho(1)-O(2) bond length. In the second Ho site, Ho(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one O(6), and two equivalent O(5) atoms. The Ho(2)-O(1) bond length is 2.24 Å. The Ho(2)-O(2) bond length is 2.39 Å. The Ho(2)-O(4) bond length is 2.53 Å. The Ho(2)-O(6) bond length is 2.20 Å. There is one shorter (2.20 Å) and one longer (2.22 Å) Ho(2)-O(5) bond length. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form distorted TiO6 pentagonal pyramids that share corners with two equivalent Ti(1)O6 pentagonal pyramids and edges with two equivalent Ho(1)O6 pentagonal pyramids. Both Ti(1)-O(1) bond lengths are 2.27 Å. There is one shorter (2.03 Å) and one longer (2.09 Å) Ti(1)-O(4) bond length. Both Ti(1)-O(5) bond lengths are 2.02 Å. In the second Ti site, Ti(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(6) atoms to form distorted TiO6 octahedra that share corners with two equivalent Ti(2)O6 octahedra, corners with two equivalent Ho(1)O6 pentagonal pyramids, and edges with four equivalent Ho(1)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 31°. Both Ti(2)-O(2) bond lengths are 2.10 Å. There is one shorter (1.89 Å) and one longer (2.39 Å) Ti(2)-O(3) bond length. Both Ti(2)-O(6) bond lengths are 1.91 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), one Ho(1), one Ho(2), and one Ti(1) atom. In the second O site, O(2) is bonded to one Ho(2), two equivalent Ho(1), and one Ti(2) atom to form OHo3Ti trigonal pyramids that share  a cornercorner with one O(4)Ho2MgTi2 trigonal bipyramid, corners with three equivalent O(2)Ho3Ti trigonal pyramids, edges with two equivalent O(3)Ho2Ti2 tetrahedra, and edges with two equivalent O(5)Ho3Ti tetrahedra. In the third O site, O(3) is bonded to two equivalent Ho(1) and two equivalent Ti(2) atoms to form distorted OHo2Ti2 tetrahedra that share corners with two equivalent O(3)Ho2Ti2 tetrahedra, corners with two equivalent O(5)Ho3Ti tetrahedra, and edges with four equivalent O(2)Ho3Ti trigonal pyramids. In the fourth O site, O(4) is bonded to one Mg(1), two equivalent Ho(2), and two equivalent Ti(1) atoms to form OHo2MgTi2 trigonal bipyramids that share corners with two equivalent O(4)Ho2MgTi2 trigonal bipyramids, corners with two equivalent O(2)Ho3Ti trigonal pyramids, and edges with four equivalent O(5)Ho3Ti tetrahedra. In the fifth O site, O(5) is bonded to one Ho(1), two equivalent Ho(2), and one Ti(1) atom to form OHo3Ti tetrahedra that share  a cornercorner with one O(3)Ho2Ti2 tetrahedra, corners with three equivalent O(5)Ho3Ti tetrahedra, edges with two equivalent O(4)Ho2MgTi2 trigonal bipyramids, and edges with two equivalent O(2)Ho3Ti trigonal pyramids. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Ho(1), one Ho(2), and one Ti(2) atom.