Eu2GeSe4 crystallizes in the monoclinic P2_1 space group. There are two inequivalent Eu sites. In the first Eu site, Eu(1) is bonded in a 7-coordinate geometry to one Se(2), two equivalent Se(1), two equivalent Se(3), and two equivalent Se(4) atoms. In the second Eu site, Eu(2) is bonded to one Se(3), two equivalent Se(1), two equivalent Se(2), and two equivalent Se(4) atoms to form distorted EuSe7 pentagonal bipyramids that share corners with two equivalent Eu(2)Se7 pentagonal bipyramids, corners with three equivalent Ge(1)Se4 tetrahedra, edges with two equivalent Eu(2)Se7 pentagonal bipyramids, and edges with two equivalent Ge(1)Se4 tetrahedra. Ge(1) is bonded to one Se(1), one Se(2), one Se(3), and one Se(4) atom to form GeSe4 tetrahedra that share corners with three equivalent Eu(2)Se7 pentagonal bipyramids and edges with two equivalent Eu(2)Se7 pentagonal bipyramids. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Eu(1), two equivalent Eu(2), and one Ge(1) atom to form a mixture of distorted corner, edge, and face-sharing SeEu4Ge square pyramids. In the second Se site, Se(2) is bonded in a distorted see-saw-like geometry to one Eu(1), two equivalent Eu(2), and one Ge(1) atom. In the third Se site, Se(3) is bonded in a distorted see-saw-like geometry to one Eu(2), two equivalent Eu(1), and one Ge(1) atom. In the fourth Se site, Se(4) is bonded to two equivalent Eu(1), two equivalent Eu(2), and one Ge(1) atom to form a mixture of corner, edge, and face-sharing SeEu4Ge square pyramids.
Eu2GeSe4 crystallizes in the monoclinic P2_1 space group. There are two inequivalent Eu sites. In the first Eu site, Eu(1) is bonded in a 7-coordinate geometry to one Se(2), two equivalent Se(1), two equivalent Se(3), and two equivalent Se(4) atoms. The Eu(1)-Se(2) bond length is 3.09 Å. There is one shorter (3.10 Å) and one longer (3.21 Å) Eu(1)-Se(1) bond length. There is one shorter (3.14 Å) and one longer (3.29 Å) Eu(1)-Se(3) bond length. There is one shorter (3.15 Å) and one longer (3.20 Å) Eu(1)-Se(4) bond length. In the second Eu site, Eu(2) is bonded to one Se(3), two equivalent Se(1), two equivalent Se(2), and two equivalent Se(4) atoms to form distorted EuSe7 pentagonal bipyramids that share corners with two equivalent Eu(2)Se7 pentagonal bipyramids, corners with three equivalent Ge(1)Se4 tetrahedra, edges with two equivalent Eu(2)Se7 pentagonal bipyramids, and edges with two equivalent Ge(1)Se4 tetrahedra. The Eu(2)-Se(3) bond length is 3.14 Å. There is one shorter (3.17 Å) and one longer (3.22 Å) Eu(2)-Se(1) bond length. There is one shorter (3.09 Å) and one longer (3.23 Å) Eu(2)-Se(2) bond length. There is one shorter (3.11 Å) and one longer (3.25 Å) Eu(2)-Se(4) bond length. Ge(1) is bonded to one Se(1), one Se(2), one Se(3), and one Se(4) atom to form GeSe4 tetrahedra that share corners with three equivalent Eu(2)Se7 pentagonal bipyramids and edges with two equivalent Eu(2)Se7 pentagonal bipyramids. The Ge(1)-Se(1) bond length is 2.40 Å. The Ge(1)-Se(2) bond length is 2.40 Å. The Ge(1)-Se(3) bond length is 2.40 Å. The Ge(1)-Se(4) bond length is 2.39 Å. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Eu(1), two equivalent Eu(2), and one Ge(1) atom to form a mixture of distorted corner, edge, and face-sharing SeEu4Ge square pyramids. In the second Se site, Se(2) is bonded in a distorted see-saw-like geometry to one Eu(1), two equivalent Eu(2), and one Ge(1) atom. In the third Se site, Se(3) is bonded in a distorted see-saw-like geometry to one Eu(2), two equivalent Eu(1), and one Ge(1) atom. In the fourth Se site, Se(4) is bonded to two equivalent Eu(1), two equivalent Eu(2), and one Ge(1) atom to form a mixture of corner, edge, and face-sharing SeEu4Ge square pyramids.