Ba2SrTm6O12 crystallizes in the trigonal P3 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. In the second Ba site, Ba(2) is bonded in a 6-coordinate geometry to six equivalent O(4) atoms. Sr(1) is bonded in a 6-coordinate geometry to six equivalent O(3) atoms. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(4) atoms to form a mixture of corner and edge-sharing TmO6 octahedra. The corner-sharing octahedral tilt angles range from 53-58°. In the second Tm site, Tm(2) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form a mixture of corner and edge-sharing TmO6 octahedra. The corner-sharing octahedral tilt angles range from 53-58°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ba(1), one Tm(1), and two equivalent Tm(2) atoms. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ba(1), one Tm(2), and two equivalent Tm(1) atoms. In the third O site, O(3) is bonded to two equivalent Sr(1), one Tm(1), and two equivalent Tm(2) atoms to form distorted OSr2Tm3 square pyramids that share corners with four equivalent O(3)Sr2Tm3 square pyramids, edges with two equivalent O(4)Ba2Tm3 square pyramids, and edges with four equivalent O(3)Sr2Tm3 square pyramids. In the fourth O site, O(4) is bonded to two equivalent Ba(2), one Tm(2), and two equivalent Tm(1) atoms to form distorted OBa2Tm3 square pyramids that share corners with four equivalent O(4)Ba2Tm3 square pyramids, edges with two equivalent O(3)Sr2Tm3 square pyramids, and edges with four equivalent O(4)Ba2Tm3 square pyramids.
Ba2SrTm6O12 crystallizes in the trigonal P3 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. All Ba(1)-O(1) bond lengths are 2.89 Å. All Ba(1)-O(2) bond lengths are 2.82 Å. In the second Ba site, Ba(2) is bonded in a 6-coordinate geometry to six equivalent O(4) atoms. There are three shorter (2.68 Å) and three longer (2.69 Å) Ba(2)-O(4) bond lengths. Sr(1) is bonded in a 6-coordinate geometry to six equivalent O(3) atoms. There are three shorter (2.56 Å) and three longer (2.58 Å) Sr(1)-O(3) bond lengths. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(4) atoms to form a mixture of corner and edge-sharing TmO6 octahedra. The corner-sharing octahedral tilt angles range from 53-58°. The Tm(1)-O(1) bond length is 2.27 Å. The Tm(1)-O(3) bond length is 2.30 Å. There is one shorter (2.25 Å) and one longer (2.26 Å) Tm(1)-O(2) bond length. There is one shorter (2.29 Å) and one longer (2.32 Å) Tm(1)-O(4) bond length. In the second Tm site, Tm(2) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form a mixture of corner and edge-sharing TmO6 octahedra. The corner-sharing octahedral tilt angles range from 53-58°. The Tm(2)-O(2) bond length is 2.23 Å. The Tm(2)-O(4) bond length is 2.26 Å. There is one shorter (2.26 Å) and one longer (2.27 Å) Tm(2)-O(1) bond length. There is one shorter (2.32 Å) and one longer (2.36 Å) Tm(2)-O(3) bond length. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ba(1), one Tm(1), and two equivalent Tm(2) atoms. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ba(1), one Tm(2), and two equivalent Tm(1) atoms. In the third O site, O(3) is bonded to two equivalent Sr(1), one Tm(1), and two equivalent Tm(2) atoms to form distorted OSr2Tm3 square pyramids that share corners with four equivalent O(3)Sr2Tm3 square pyramids, edges with two equivalent O(4)Ba2Tm3 square pyramids, and edges with four equivalent O(3)Sr2Tm3 square pyramids. In the fourth O site, O(4) is bonded to two equivalent Ba(2), one Tm(2), and two equivalent Tm(1) atoms to form distorted OBa2Tm3 square pyramids that share corners with four equivalent O(4)Ba2Tm3 square pyramids, edges with two equivalent O(3)Sr2Tm3 square pyramids, and edges with four equivalent O(4)Ba2Tm3 square pyramids.