BaCu2GeSe4 crystallizes in the trigonal P3_121 space group. Ba(1) is bonded in a 8-coordinate geometry to four equivalent Se(1) and four equivalent Se(2) atoms. Cu(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form distorted CuSe4 tetrahedra that share corners with four equivalent Cu(1)Se4 tetrahedra and corners with four equivalent Ge(1)Se4 tetrahedra. Ge(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form GeSe4 tetrahedra that share corners with eight equivalent Cu(1)Se4 tetrahedra. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 5-coordinate geometry to two equivalent Ba(1), two equivalent Cu(1), and one Ge(1) atom. In the second Se site, Se(2) is bonded to two equivalent Ba(1), two equivalent Cu(1), and one Ge(1) atom to form a mixture of distorted edge and corner-sharing SeBa2Cu2Ge trigonal bipyramids.
BaCu2GeSe4 crystallizes in the trigonal P3_121 space group. Ba(1) is bonded in a 8-coordinate geometry to four equivalent Se(1) and four equivalent Se(2) atoms. There are two shorter (3.40 Å) and two longer (3.41 Å) Ba(1)-Se(1) bond lengths. All Ba(1)-Se(2) bond lengths are 3.35 Å. Cu(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form distorted CuSe4 tetrahedra that share corners with four equivalent Cu(1)Se4 tetrahedra and corners with four equivalent Ge(1)Se4 tetrahedra. There is one shorter (2.45 Å) and one longer (2.52 Å) Cu(1)-Se(1) bond length. Both Cu(1)-Se(2) bond lengths are 2.47 Å. Ge(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form GeSe4 tetrahedra that share corners with eight equivalent Cu(1)Se4 tetrahedra. Both Ge(1)-Se(1) bond lengths are 2.42 Å. Both Ge(1)-Se(2) bond lengths are 2.43 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 5-coordinate geometry to two equivalent Ba(1), two equivalent Cu(1), and one Ge(1) atom. In the second Se site, Se(2) is bonded to two equivalent Ba(1), two equivalent Cu(1), and one Ge(1) atom to form a mixture of distorted edge and corner-sharing SeBa2Cu2Ge trigonal bipyramids.