Ba3Fe3Se7 crystallizes in the hexagonal P6_3mc space group. Ba(1) is bonded in a 8-coordinate geometry to one Se(3), three equivalent Se(1), and four equivalent Se(2) atoms. Fe(1) is bonded to one Se(1), one Se(3), and two equivalent Se(2) atoms to form distorted edge-sharing FeSe4 tetrahedra. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Ba(1) and one Fe(1) atom to form distorted SeBa3Fe trigonal pyramids that share corners with two equivalent Se(3)Ba3Fe3 pentagonal pyramids, corners with six equivalent Se(1)Ba3Fe trigonal pyramids, and  an edgeedge with one Se(3)Ba3Fe3 pentagonal pyramid. In the second Se site, Se(2) is bonded in a 6-coordinate geometry to four equivalent Ba(1) and two equivalent Fe(1) atoms. In the third Se site, Se(3) is bonded to three equivalent Ba(1) and three equivalent Fe(1) atoms to form a mixture of distorted corner and edge-sharing SeBa3Fe3 pentagonal pyramids.
Ba3Fe3Se7 crystallizes in the hexagonal P6_3mc space group. Ba(1) is bonded in a 8-coordinate geometry to one Se(3), three equivalent Se(1), and four equivalent Se(2) atoms. The Ba(1)-Se(3) bond length is 3.39 Å. There are two shorter (3.23 Å) and one longer (3.28 Å) Ba(1)-Se(1) bond length. There are two shorter (3.46 Å) and two longer (3.85 Å) Ba(1)-Se(2) bond lengths. Fe(1) is bonded to one Se(1), one Se(3), and two equivalent Se(2) atoms to form distorted edge-sharing FeSe4 tetrahedra. The Fe(1)-Se(1) bond length is 2.33 Å. The Fe(1)-Se(3) bond length is 2.42 Å. Both Fe(1)-Se(2) bond lengths are 2.41 Å. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Ba(1) and one Fe(1) atom to form distorted SeBa3Fe trigonal pyramids that share corners with two equivalent Se(3)Ba3Fe3 pentagonal pyramids, corners with six equivalent Se(1)Ba3Fe trigonal pyramids, and  an edgeedge with one Se(3)Ba3Fe3 pentagonal pyramid. In the second Se site, Se(2) is bonded in a 6-coordinate geometry to four equivalent Ba(1) and two equivalent Fe(1) atoms. In the third Se site, Se(3) is bonded to three equivalent Ba(1) and three equivalent Fe(1) atoms to form a mixture of distorted corner and edge-sharing SeBa3Fe3 pentagonal pyramids.