Ba2SnSe4 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to two equivalent Se(1), two equivalent Se(2), two equivalent Se(4), and three equivalent Se(3) atoms. In the second Ba site, Ba(2) is bonded in a 7-coordinate geometry to one Se(3), two equivalent Se(1), two equivalent Se(2), and two equivalent Se(4) atoms. Sn(1) is bonded in a tetrahedral geometry to one Se(1), one Se(2), one Se(3), and one Se(4) atom. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Ba(1), two equivalent Ba(2), and one Sn(1) atom to form a mixture of distorted edge and corner-sharing SeBa4Sn trigonal bipyramids. In the second Se site, Se(2) is bonded to two equivalent Ba(1), two equivalent Ba(2), and one Sn(1) atom to form a mixture of distorted edge and corner-sharing SeBa4Sn trigonal bipyramids. In the third Se site, Se(3) is bonded to one Ba(2), three equivalent Ba(1), and one Sn(1) atom to form a mixture of distorted edge and corner-sharing SeBa4Sn trigonal bipyramids. In the fourth Se site, Se(4) is bonded in a 5-coordinate geometry to two equivalent Ba(1), two equivalent Ba(2), and one Sn(1) atom.
Ba2SnSe4 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to two equivalent Se(1), two equivalent Se(2), two equivalent Se(4), and three equivalent Se(3) atoms. There is one shorter (3.29 Å) and one longer (3.67 Å) Ba(1)-Se(1) bond length. There is one shorter (3.40 Å) and one longer (3.61 Å) Ba(1)-Se(2) bond length. There is one shorter (3.72 Å) and one longer (3.83 Å) Ba(1)-Se(4) bond length. There are a spread of Ba(1)-Se(3) bond distances ranging from 3.40-3.48 Å. In the second Ba site, Ba(2) is bonded in a 7-coordinate geometry to one Se(3), two equivalent Se(1), two equivalent Se(2), and two equivalent Se(4) atoms. The Ba(2)-Se(3) bond length is 3.38 Å. There is one shorter (3.23 Å) and one longer (3.43 Å) Ba(2)-Se(1) bond length. There is one shorter (3.31 Å) and one longer (3.38 Å) Ba(2)-Se(2) bond length. There is one shorter (3.48 Å) and one longer (3.68 Å) Ba(2)-Se(4) bond length. Sn(1) is bonded in a tetrahedral geometry to one Se(1), one Se(2), one Se(3), and one Se(4) atom. The Sn(1)-Se(1) bond length is 2.53 Å. The Sn(1)-Se(2) bond length is 2.54 Å. The Sn(1)-Se(3) bond length is 2.55 Å. The Sn(1)-Se(4) bond length is 2.51 Å. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Ba(1), two equivalent Ba(2), and one Sn(1) atom to form a mixture of distorted edge and corner-sharing SeBa4Sn trigonal bipyramids. In the second Se site, Se(2) is bonded to two equivalent Ba(1), two equivalent Ba(2), and one Sn(1) atom to form a mixture of distorted edge and corner-sharing SeBa4Sn trigonal bipyramids. In the third Se site, Se(3) is bonded to one Ba(2), three equivalent Ba(1), and one Sn(1) atom to form a mixture of distorted edge and corner-sharing SeBa4Sn trigonal bipyramids. In the fourth Se site, Se(4) is bonded in a 5-coordinate geometry to two equivalent Ba(1), two equivalent Ba(2), and one Sn(1) atom.