NbV(Cu3Se4)2 is Sulvanite-derived structured and crystallizes in the tetragonal P-42m space group. Nb(1) is bonded to four equivalent Se(1) atoms to form distorted NbSe4 tetrahedra that share edges with two equivalent Cu(1)Se4 tetrahedra and edges with four equivalent Cu(2)Se4 tetrahedra. V(1) is bonded to four equivalent Se(2) atoms to form VSe4 tetrahedra that share edges with two equivalent Cu(1)Se4 tetrahedra and edges with four equivalent Cu(3)Se4 tetrahedra. There are three inequivalent Cu sites. In the first Cu site, 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(2)Se4 tetrahedra, corners with four equivalent Cu(3)Se4 tetrahedra,  an edgeedge with one Nb(1)Se4 tetrahedra, and  an edgeedge with one V(1)Se4 tetrahedra. In the second Cu site, Cu(2) is bonded to four equivalent Se(1) atoms to form distorted CuSe4 tetrahedra that share corners with four equivalent Cu(1)Se4 tetrahedra, corners with four equivalent Cu(2)Se4 tetrahedra, and edges with two equivalent Nb(1)Se4 tetrahedra. In the third Cu site, Cu(3) is bonded to four equivalent Se(2) atoms to form distorted CuSe4 tetrahedra that share corners with four equivalent Cu(1)Se4 tetrahedra, corners with four equivalent Cu(3)Se4 tetrahedra, and edges with two equivalent V(1)Se4 tetrahedra. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to one Nb(1), one Cu(1), and two equivalent Cu(2) atoms to form SeNbCu3 tetrahedra that share corners with two equivalent Se(2)VCu3 tetrahedra, corners with four equivalent Se(1)NbCu3 tetrahedra, and edges with three equivalent Se(1)NbCu3 tetrahedra. In the second Se site, Se(2) is bonded to one V(1), one Cu(1), and two equivalent Cu(3) atoms to form SeVCu3 tetrahedra that share corners with two equivalent Se(1)NbCu3 tetrahedra, corners with four equivalent Se(2)VCu3 tetrahedra, and edges with three equivalent Se(2)VCu3 tetrahedra.
NbV(Cu3Se4)2 is Sulvanite-derived structured and crystallizes in the tetragonal P-42m space group. Nb(1) is bonded to four equivalent Se(1) atoms to form distorted NbSe4 tetrahedra that share edges with two equivalent Cu(1)Se4 tetrahedra and edges with four equivalent Cu(2)Se4 tetrahedra. All Nb(1)-Se(1) bond lengths are 2.47 Å. V(1) is bonded to four equivalent Se(2) atoms to form VSe4 tetrahedra that share edges with two equivalent Cu(1)Se4 tetrahedra and edges with four equivalent Cu(3)Se4 tetrahedra. All V(1)-Se(2) bond lengths are 2.36 Å. There are three inequivalent Cu sites. In the first Cu site, 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(2)Se4 tetrahedra, corners with four equivalent Cu(3)Se4 tetrahedra,  an edgeedge with one Nb(1)Se4 tetrahedra, and  an edgeedge with one V(1)Se4 tetrahedra. Both Cu(1)-Se(1) bond lengths are 2.46 Å. Both Cu(1)-Se(2) bond lengths are 2.41 Å. In the second Cu site, Cu(2) is bonded to four equivalent Se(1) atoms to form distorted CuSe4 tetrahedra that share corners with four equivalent Cu(1)Se4 tetrahedra, corners with four equivalent Cu(2)Se4 tetrahedra, and edges with two equivalent Nb(1)Se4 tetrahedra. All Cu(2)-Se(1) bond lengths are 2.45 Å. In the third Cu site, Cu(3) is bonded to four equivalent Se(2) atoms to form distorted CuSe4 tetrahedra that share corners with four equivalent Cu(1)Se4 tetrahedra, corners with four equivalent Cu(3)Se4 tetrahedra, and edges with two equivalent V(1)Se4 tetrahedra. All Cu(3)-Se(2) bond lengths are 2.42 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to one Nb(1), one Cu(1), and two equivalent Cu(2) atoms to form SeNbCu3 tetrahedra that share corners with two equivalent Se(2)VCu3 tetrahedra, corners with four equivalent Se(1)NbCu3 tetrahedra, and edges with three equivalent Se(1)NbCu3 tetrahedra. In the second Se site, Se(2) is bonded to one V(1), one Cu(1), and two equivalent Cu(3) atoms to form SeVCu3 tetrahedra that share corners with two equivalent Se(1)NbCu3 tetrahedra, corners with four equivalent Se(2)VCu3 tetrahedra, and edges with three equivalent Se(2)VCu3 tetrahedra.