MgYb4Ti2O10 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 5-coordinate geometry to one O(1), one O(4), one O(7), one O(8), and one O(9) atom. There are four inequivalent Yb sites. In the first Yb site, Yb(1) is bonded to one O(1), one O(3), one O(4), and one O(9) atom to form YbO4 tetrahedra that share  a cornercorner with one Yb(4)O6 octahedra and corners with two equivalent Ti(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 78°. In the second Yb site, Yb(2) is bonded in a 6-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(5), and one O(6) atom. In the third Yb site, Yb(3) is bonded in a 6-coordinate geometry to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom. In the fourth Yb site, Yb(4) is bonded to one O(10), one O(2), one O(5), one O(6), one O(7), and one O(9) atom to form distorted YbO6 octahedra that share  a cornercorner with one Yb(1)O4 tetrahedra and corners with three equivalent Ti(2)O5 trigonal bipyramids. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(3), one O(6), one O(7), and one O(8) atom. In the second Ti site, Ti(2) is bonded to one O(1), one O(10), one O(5), one O(8), and one O(9) atom to form distorted TiO5 trigonal bipyramids that share corners with three equivalent Yb(4)O6 octahedra and corners with two equivalent Yb(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 38-59°. There are ten inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Yb(1), one Yb(2), and one Ti(2) atom to form OYb2MgTi tetrahedra that share corners with three equivalent O(9)Yb2MgTi tetrahedra,  a cornercorner with one O(6)Yb3Ti trigonal pyramid, corners with two equivalent O(3)Yb3Ti trigonal pyramids, and corners with two equivalent O(5)Yb3Ti trigonal pyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Yb(2), one Yb(3), one Yb(4), and one Ti(1) atom. In the third O site, O(3) is bonded to one Yb(1), one Yb(2), one Yb(3), and one Ti(1) atom to form distorted OYb3Ti trigonal pyramids that share  a cornercorner with one O(9)Yb2MgTi tetrahedra, corners with two equivalent O(1)Yb2MgTi tetrahedra,  a cornercorner with one O(6)Yb3Ti trigonal pyramid, corners with two equivalent O(5)Yb3Ti trigonal pyramids, and  an edgeedge with one O(6)Yb3Ti trigonal pyramid. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Mg(1), one Yb(1), and one Yb(3) atom. In the fifth O site, O(5) is bonded to one Yb(2), one Yb(3), one Yb(4), and one Ti(2) atom to form distorted OYb3Ti trigonal pyramids that share corners with two equivalent O(1)Yb2MgTi tetrahedra, corners with two equivalent O(9)Yb2MgTi tetrahedra,  a cornercorner with one O(6)Yb3Ti trigonal pyramid, corners with two equivalent O(3)Yb3Ti trigonal pyramids, and  an edgeedge with one O(6)Yb3Ti trigonal pyramid. In the sixth O site, O(6) is bonded to one Yb(2), one Yb(3), one Yb(4), and one Ti(1) atom to form distorted OYb3Ti trigonal pyramids that share  a cornercorner with one O(1)Yb2MgTi tetrahedra,  a cornercorner with one O(9)Yb2MgTi tetrahedra,  a cornercorner with one O(3)Yb3Ti trigonal pyramid,  a cornercorner with one O(5)Yb3Ti trigonal pyramid,  an edgeedge with one O(3)Yb3Ti trigonal pyramid, and  an edgeedge with one O(5)Yb3Ti trigonal pyramid. In the seventh O site, O(7) is bonded in a distorted see-saw-like geometry to one Mg(1), one Yb(3), one Yb(4), and one Ti(1) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ti(1), and one Ti(2) atom. In the ninth O site, O(9) is bonded to one Mg(1), one Yb(1), one Yb(4), and one Ti(2) atom to form OYb2MgTi tetrahedra that share corners with three equivalent O(1)Yb2MgTi tetrahedra,  a cornercorner with one O(3)Yb3Ti trigonal pyramid,  a cornercorner with one O(6)Yb3Ti trigonal pyramid, and corners with two equivalent O(5)Yb3Ti trigonal pyramids. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Yb(2), one Yb(4), one Ti(1), and one Ti(2) atom.
MgYb4Ti2O10 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 5-coordinate geometry to one O(1), one O(4), one O(7), one O(8), and one O(9) atom. The Mg(1)-O(1) bond length is 1.98 Å. The Mg(1)-O(4) bond length is 1.99 Å. The Mg(1)-O(7) bond length is 2.11 Å. The Mg(1)-O(8) bond length is 2.06 Å. The Mg(1)-O(9) bond length is 2.10 Å. There are four inequivalent Yb sites. In the first Yb site, Yb(1) is bonded to one O(1), one O(3), one O(4), and one O(9) atom to form YbO4 tetrahedra that share  a cornercorner with one Yb(4)O6 octahedra and corners with two equivalent Ti(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 78°. The Yb(1)-O(1) bond length is 2.25 Å. The Yb(1)-O(3) bond length is 2.19 Å. The Yb(1)-O(4) bond length is 2.21 Å. The Yb(1)-O(9) bond length is 2.30 Å. In the second Yb site, Yb(2) is bonded in a 6-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(5), and one O(6) atom. The Yb(2)-O(1) bond length is 2.32 Å. The Yb(2)-O(10) bond length is 2.33 Å. The Yb(2)-O(2) bond length is 2.38 Å. The Yb(2)-O(3) bond length is 2.40 Å. The Yb(2)-O(5) bond length is 2.34 Å. The Yb(2)-O(6) bond length is 2.26 Å. In the third Yb site, Yb(3) is bonded in a 6-coordinate geometry to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom. The Yb(3)-O(2) bond length is 2.26 Å. The Yb(3)-O(3) bond length is 2.18 Å. The Yb(3)-O(4) bond length is 2.23 Å. The Yb(3)-O(5) bond length is 2.34 Å. The Yb(3)-O(6) bond length is 2.36 Å. The Yb(3)-O(7) bond length is 2.33 Å. In the fourth Yb site, Yb(4) is bonded to one O(10), one O(2), one O(5), one O(6), one O(7), and one O(9) atom to form distorted YbO6 octahedra that share  a cornercorner with one Yb(1)O4 tetrahedra and corners with three equivalent Ti(2)O5 trigonal bipyramids. The Yb(4)-O(10) bond length is 2.43 Å. The Yb(4)-O(2) bond length is 2.32 Å. The Yb(4)-O(5) bond length is 2.35 Å. The Yb(4)-O(6) bond length is 2.32 Å. The Yb(4)-O(7) bond length is 2.37 Å. The Yb(4)-O(9) bond length is 2.27 Å. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(3), one O(6), one O(7), and one O(8) atom. The Ti(1)-O(10) bond length is 2.42 Å. The Ti(1)-O(2) bond length is 2.02 Å. The Ti(1)-O(3) bond length is 2.06 Å. The Ti(1)-O(6) bond length is 1.91 Å. The Ti(1)-O(7) bond length is 1.96 Å. The Ti(1)-O(8) bond length is 1.84 Å. In the second Ti site, Ti(2) is bonded to one O(1), one O(10), one O(5), one O(8), and one O(9) atom to form distorted TiO5 trigonal bipyramids that share corners with three equivalent Yb(4)O6 octahedra and corners with two equivalent Yb(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 38-59°. The Ti(2)-O(1) bond length is 1.92 Å. The Ti(2)-O(10) bond length is 1.93 Å. The Ti(2)-O(5) bond length is 1.83 Å. The Ti(2)-O(8) bond length is 2.12 Å. The Ti(2)-O(9) bond length is 1.93 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Yb(1), one Yb(2), and one Ti(2) atom to form OYb2MgTi tetrahedra that share corners with three equivalent O(9)Yb2MgTi tetrahedra,  a cornercorner with one O(6)Yb3Ti trigonal pyramid, corners with two equivalent O(3)Yb3Ti trigonal pyramids, and corners with two equivalent O(5)Yb3Ti trigonal pyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Yb(2), one Yb(3), one Yb(4), and one Ti(1) atom. In the third O site, O(3) is bonded to one Yb(1), one Yb(2), one Yb(3), and one Ti(1) atom to form distorted OYb3Ti trigonal pyramids that share  a cornercorner with one O(9)Yb2MgTi tetrahedra, corners with two equivalent O(1)Yb2MgTi tetrahedra,  a cornercorner with one O(6)Yb3Ti trigonal pyramid, corners with two equivalent O(5)Yb3Ti trigonal pyramids, and  an edgeedge with one O(6)Yb3Ti trigonal pyramid. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Mg(1), one Yb(1), and one Yb(3) atom. In the fifth O site, O(5) is bonded to one Yb(2), one Yb(3), one Yb(4), and one Ti(2) atom to form distorted OYb3Ti trigonal pyramids that share corners with two equivalent O(1)Yb2MgTi tetrahedra, corners with two equivalent O(9)Yb2MgTi tetrahedra,  a cornercorner with one O(6)Yb3Ti trigonal pyramid, corners with two equivalent O(3)Yb3Ti trigonal pyramids, and  an edgeedge with one O(6)Yb3Ti trigonal pyramid. In the sixth O site, O(6) is bonded to one Yb(2), one Yb(3), one Yb(4), and one Ti(1) atom to form distorted OYb3Ti trigonal pyramids that share  a cornercorner with one O(1)Yb2MgTi tetrahedra,  a cornercorner with one O(9)Yb2MgTi tetrahedra,  a cornercorner with one O(3)Yb3Ti trigonal pyramid,  a cornercorner with one O(5)Yb3Ti trigonal pyramid,  an edgeedge with one O(3)Yb3Ti trigonal pyramid, and  an edgeedge with one O(5)Yb3Ti trigonal pyramid. In the seventh O site, O(7) is bonded in a distorted see-saw-like geometry to one Mg(1), one Yb(3), one Yb(4), and one Ti(1) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ti(1), and one Ti(2) atom. In the ninth O site, O(9) is bonded to one Mg(1), one Yb(1), one Yb(4), and one Ti(2) atom to form OYb2MgTi tetrahedra that share corners with three equivalent O(1)Yb2MgTi tetrahedra,  a cornercorner with one O(3)Yb3Ti trigonal pyramid,  a cornercorner with one O(6)Yb3Ti trigonal pyramid, and corners with two equivalent O(5)Yb3Ti trigonal pyramids. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Yb(2), one Yb(4), one Ti(1), and one Ti(2) atom.