TmGaO3 crystallizes in the hexagonal P6_3cm space group. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded in a 7-coordinate geometry to one O(3), three equivalent O(1), and three equivalent O(2) atoms. In the second Tm site, Tm(2) is bonded to one O(4), three equivalent O(1), and three equivalent O(2) atoms to form distorted TmO7 pentagonal bipyramids that share corners with three equivalent Ga(1)O5 trigonal bipyramids and edges with three equivalent Ga(1)O5 trigonal bipyramids. Ga(1) is bonded to one O(1), one O(2), one O(4), and two equivalent O(3) atoms to form GaO5 trigonal bipyramids that share  a cornercorner with one Tm(2)O7 pentagonal bipyramid, corners with six equivalent Ga(1)O5 trigonal bipyramids, and  an edgeedge with one Tm(2)O7 pentagonal bipyramid. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Tm(2), two equivalent Tm(1), and one Ga(1) atom to form OTm3Ga tetrahedra that share corners with four equivalent O(2)Tm3Ga tetrahedra, corners with six equivalent O(1)Tm3Ga tetrahedra, corners with two equivalent O(4)TmGa3 trigonal pyramids, edges with three equivalent O(2)Tm3Ga tetrahedra, and edges with two equivalent O(3)TmGa3 trigonal pyramids. In the second O site, O(2) is bonded to one Tm(2), two equivalent Tm(1), and one Ga(1) atom to form distorted OTm3Ga tetrahedra that share corners with four equivalent O(1)Tm3Ga tetrahedra, corners with six equivalent O(2)Tm3Ga tetrahedra, corners with four equivalent O(3)TmGa3 trigonal pyramids, edges with three equivalent O(1)Tm3Ga tetrahedra, and  an edgeedge with one O(4)TmGa3 trigonal pyramid. In the third O site, O(3) is bonded to one Tm(1) and three equivalent Ga(1) atoms to form distorted OTmGa3 trigonal pyramids that share corners with six equivalent O(2)Tm3Ga tetrahedra, corners with three equivalent O(3)TmGa3 trigonal pyramids, corners with three equivalent O(4)TmGa3 trigonal pyramids, and edges with three equivalent O(1)Tm3Ga tetrahedra. In the fourth O site, O(4) is bonded to one Tm(2) and three equivalent Ga(1) atoms to form OTmGa3 trigonal pyramids that share corners with six equivalent O(1)Tm3Ga tetrahedra, corners with six equivalent O(3)TmGa3 trigonal pyramids, and edges with three equivalent O(2)Tm3Ga tetrahedra.
TmGaO3 crystallizes in the hexagonal P6_3cm space group. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded in a 7-coordinate geometry to one O(3), three equivalent O(1), and three equivalent O(2) atoms. The Tm(1)-O(3) bond length is 2.47 Å. All Tm(1)-O(1) bond lengths are 2.22 Å. All Tm(1)-O(2) bond lengths are 2.26 Å. In the second Tm site, Tm(2) is bonded to one O(4), three equivalent O(1), and three equivalent O(2) atoms to form distorted TmO7 pentagonal bipyramids that share corners with three equivalent Ga(1)O5 trigonal bipyramids and edges with three equivalent Ga(1)O5 trigonal bipyramids. The Tm(2)-O(4) bond length is 2.34 Å. All Tm(2)-O(1) bond lengths are 2.23 Å. All Tm(2)-O(2) bond lengths are 2.27 Å. Ga(1) is bonded to one O(1), one O(2), one O(4), and two equivalent O(3) atoms to form GaO5 trigonal bipyramids that share  a cornercorner with one Tm(2)O7 pentagonal bipyramid, corners with six equivalent Ga(1)O5 trigonal bipyramids, and  an edgeedge with one Tm(2)O7 pentagonal bipyramid. The Ga(1)-O(1) bond length is 1.91 Å. The Ga(1)-O(2) bond length is 1.89 Å. The Ga(1)-O(4) bond length is 2.01 Å. Both Ga(1)-O(3) bond lengths are 2.00 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Tm(2), two equivalent Tm(1), and one Ga(1) atom to form OTm3Ga tetrahedra that share corners with four equivalent O(2)Tm3Ga tetrahedra, corners with six equivalent O(1)Tm3Ga tetrahedra, corners with two equivalent O(4)TmGa3 trigonal pyramids, edges with three equivalent O(2)Tm3Ga tetrahedra, and edges with two equivalent O(3)TmGa3 trigonal pyramids. In the second O site, O(2) is bonded to one Tm(2), two equivalent Tm(1), and one Ga(1) atom to form distorted OTm3Ga tetrahedra that share corners with four equivalent O(1)Tm3Ga tetrahedra, corners with six equivalent O(2)Tm3Ga tetrahedra, corners with four equivalent O(3)TmGa3 trigonal pyramids, edges with three equivalent O(1)Tm3Ga tetrahedra, and  an edgeedge with one O(4)TmGa3 trigonal pyramid. In the third O site, O(3) is bonded to one Tm(1) and three equivalent Ga(1) atoms to form distorted OTmGa3 trigonal pyramids that share corners with six equivalent O(2)Tm3Ga tetrahedra, corners with three equivalent O(3)TmGa3 trigonal pyramids, corners with three equivalent O(4)TmGa3 trigonal pyramids, and edges with three equivalent O(1)Tm3Ga tetrahedra. In the fourth O site, O(4) is bonded to one Tm(2) and three equivalent Ga(1) atoms to form OTmGa3 trigonal pyramids that share corners with six equivalent O(1)Tm3Ga tetrahedra, corners with six equivalent O(3)TmGa3 trigonal pyramids, and edges with three equivalent O(2)Tm3Ga tetrahedra.