EuTm2Se4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded to one Se(1), two equivalent Se(3), and three equivalent Se(2) atoms to form a mixture of corner and edge-sharing TmSe6 octahedra. The corner-sharing octahedral tilt angles range from 48-64°. In the second Tm site, Tm(2) is bonded to one Se(3), two equivalent Se(1), and three equivalent Se(4) atoms to form a mixture of corner and edge-sharing TmSe6 octahedra. The corner-sharing octahedral tilt angles range from 48-64°. Eu(1) is bonded in a 8-coordinate geometry to two equivalent Se(1), two equivalent Se(2), two equivalent Se(3), and two equivalent Se(4) atoms. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to one Tm(1), two equivalent Tm(2), and two equivalent Eu(1) atoms to form a mixture of distorted corner and edge-sharing SeEu2Tm3 trigonal bipyramids. In the second Se site, Se(2) is bonded to three equivalent Tm(1) and two equivalent Eu(1) atoms to form a mixture of corner and edge-sharing SeEu2Tm3 square pyramids. In the third Se site, Se(3) is bonded to one Tm(2), two equivalent Tm(1), and two equivalent Eu(1) atoms to form a mixture of distorted corner and edge-sharing SeEu2Tm3 trigonal bipyramids. In the fourth Se site, Se(4) is bonded to three equivalent Tm(2) and two equivalent Eu(1) atoms to form a mixture of distorted corner and edge-sharing SeEu2Tm3 trigonal bipyramids.
EuTm2Se4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded to one Se(1), two equivalent Se(3), and three equivalent Se(2) atoms to form a mixture of corner and edge-sharing TmSe6 octahedra. The corner-sharing octahedral tilt angles range from 48-64°. The Tm(1)-Se(1) bond length is 2.84 Å. Both Tm(1)-Se(3) bond lengths are 2.76 Å. There is one shorter (2.82 Å) and two longer (2.84 Å) Tm(1)-Se(2) bond lengths. In the second Tm site, Tm(2) is bonded to one Se(3), two equivalent Se(1), and three equivalent Se(4) atoms to form a mixture of corner and edge-sharing TmSe6 octahedra. The corner-sharing octahedral tilt angles range from 48-64°. The Tm(2)-Se(3) bond length is 2.77 Å. Both Tm(2)-Se(1) bond lengths are 2.85 Å. There is one shorter (2.80 Å) and two longer (2.83 Å) Tm(2)-Se(4) bond lengths. Eu(1) is bonded in a 8-coordinate geometry to two equivalent Se(1), two equivalent Se(2), two equivalent Se(3), and two equivalent Se(4) atoms. Both Eu(1)-Se(1) bond lengths are 3.14 Å. Both Eu(1)-Se(2) bond lengths are 3.14 Å. There is one shorter (3.36 Å) and one longer (3.41 Å) Eu(1)-Se(3) bond length. Both Eu(1)-Se(4) bond lengths are 3.17 Å. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to one Tm(1), two equivalent Tm(2), and two equivalent Eu(1) atoms to form a mixture of distorted corner and edge-sharing SeEu2Tm3 trigonal bipyramids. In the second Se site, Se(2) is bonded to three equivalent Tm(1) and two equivalent Eu(1) atoms to form a mixture of corner and edge-sharing SeEu2Tm3 square pyramids. In the third Se site, Se(3) is bonded to one Tm(2), two equivalent Tm(1), and two equivalent Eu(1) atoms to form a mixture of distorted corner and edge-sharing SeEu2Tm3 trigonal bipyramids. In the fourth Se site, Se(4) is bonded to three equivalent Tm(2) and two equivalent Eu(1) atoms to form a mixture of distorted corner and edge-sharing SeEu2Tm3 trigonal bipyramids.