Nb2CuS4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 8-coordinate geometry to one S(1), two equivalent S(2), two equivalent S(4), and three equivalent S(3) atoms. In the second Nb site, Nb(2) is bonded to one S(2), two equivalent S(1), and three equivalent S(4) atoms to form distorted NbS6 octahedra that share corners with three equivalent Cu(1)S6 octahedra, edges with two equivalent Cu(1)S6 octahedra, and edges with four equivalent Nb(2)S6 octahedra. The corner-sharing octahedral tilt angles range from 34-49°. Cu(1) is bonded to one S(1), one S(4), two equivalent S(2), and two equivalent S(3) atoms to form distorted CuS6 octahedra that share corners with three equivalent Nb(2)S6 octahedra, edges with two equivalent Nb(2)S6 octahedra, and edges with two equivalent Cu(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 34-49°. There are four inequivalent S sites. In the first S site, S(1) is bonded to one Nb(1), two equivalent Nb(2), and one Cu(1) atom to form distorted SNb3Cu tetrahedra that share corners with three equivalent S(4)Nb5Cu octahedra, corners with two equivalent S(1)Nb3Cu tetrahedra, corners with two equivalent S(2)Nb3Cu2 trigonal bipyramids, corners with five equivalent S(3)Nb3Cu2 trigonal bipyramids, edges with three equivalent S(4)Nb5Cu octahedra, and edges with two equivalent S(2)Nb3Cu2 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 1-9°. In the second S site, S(2) is bonded to one Nb(2), two equivalent Nb(1), and two equivalent Cu(1) atoms to form distorted SNb3Cu2 trigonal bipyramids that share corners with three equivalent S(4)Nb5Cu octahedra, corners with two equivalent S(1)Nb3Cu tetrahedra, corners with six equivalent S(3)Nb3Cu2 trigonal bipyramids, edges with three equivalent S(4)Nb5Cu octahedra, edges with two equivalent S(1)Nb3Cu tetrahedra, edges with two equivalent S(2)Nb3Cu2 trigonal bipyramids, and edges with two equivalent S(3)Nb3Cu2 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 31-35°. In the third S site, S(3) is bonded to three equivalent Nb(1) and two equivalent Cu(1) atoms to form distorted SNb3Cu2 trigonal bipyramids that share corners with two equivalent S(4)Nb5Cu octahedra, corners with five equivalent S(1)Nb3Cu tetrahedra, corners with six equivalent S(2)Nb3Cu2 trigonal bipyramids, edges with three equivalent S(4)Nb5Cu octahedra, edges with two equivalent S(2)Nb3Cu2 trigonal bipyramids, and edges with four equivalent S(3)Nb3Cu2 trigonal bipyramids. The corner-sharing octahedral tilt angles are 39°. In the fourth S site, S(4) is bonded to two equivalent Nb(1), three equivalent Nb(2), and one Cu(1) atom to form distorted SNb5Cu octahedra that share corners with three equivalent S(1)Nb3Cu tetrahedra, corners with two equivalent S(3)Nb3Cu2 trigonal bipyramids, corners with three equivalent S(2)Nb3Cu2 trigonal bipyramids, edges with four equivalent S(4)Nb5Cu octahedra, edges with three equivalent S(1)Nb3Cu tetrahedra, edges with three equivalent S(2)Nb3Cu2 trigonal bipyramids, and edges with three equivalent S(3)Nb3Cu2 trigonal bipyramids.
Nb2CuS4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 8-coordinate geometry to one S(1), two equivalent S(2), two equivalent S(4), and three equivalent S(3) atoms. The Nb(1)-S(1) bond length is 2.60 Å. Both Nb(1)-S(2) bond lengths are 2.55 Å. Both Nb(1)-S(4) bond lengths are 2.80 Å. There are two shorter (2.57 Å) and one longer (2.64 Å) Nb(1)-S(3) bond length. In the second Nb site, Nb(2) is bonded to one S(2), two equivalent S(1), and three equivalent S(4) atoms to form distorted NbS6 octahedra that share corners with three equivalent Cu(1)S6 octahedra, edges with two equivalent Cu(1)S6 octahedra, and edges with four equivalent Nb(2)S6 octahedra. The corner-sharing octahedral tilt angles range from 34-49°. The Nb(2)-S(2) bond length is 2.61 Å. Both Nb(2)-S(1) bond lengths are 2.48 Å. There is one shorter (2.53 Å) and two longer (2.64 Å) Nb(2)-S(4) bond lengths. Cu(1) is bonded to one S(1), one S(4), two equivalent S(2), and two equivalent S(3) atoms to form distorted CuS6 octahedra that share corners with three equivalent Nb(2)S6 octahedra, edges with two equivalent Nb(2)S6 octahedra, and edges with two equivalent Cu(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 34-49°. The Cu(1)-S(1) bond length is 2.28 Å. The Cu(1)-S(4) bond length is 2.37 Å. Both Cu(1)-S(2) bond lengths are 2.57 Å. Both Cu(1)-S(3) bond lengths are 2.62 Å. There are four inequivalent S sites. In the first S site, S(1) is bonded to one Nb(1), two equivalent Nb(2), and one Cu(1) atom to form distorted SNb3Cu tetrahedra that share corners with three equivalent S(4)Nb5Cu octahedra, corners with two equivalent S(1)Nb3Cu tetrahedra, corners with two equivalent S(2)Nb3Cu2 trigonal bipyramids, corners with five equivalent S(3)Nb3Cu2 trigonal bipyramids, edges with three equivalent S(4)Nb5Cu octahedra, and edges with two equivalent S(2)Nb3Cu2 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 1-9°. In the second S site, S(2) is bonded to one Nb(2), two equivalent Nb(1), and two equivalent Cu(1) atoms to form distorted SNb3Cu2 trigonal bipyramids that share corners with three equivalent S(4)Nb5Cu octahedra, corners with two equivalent S(1)Nb3Cu tetrahedra, corners with six equivalent S(3)Nb3Cu2 trigonal bipyramids, edges with three equivalent S(4)Nb5Cu octahedra, edges with two equivalent S(1)Nb3Cu tetrahedra, edges with two equivalent S(2)Nb3Cu2 trigonal bipyramids, and edges with two equivalent S(3)Nb3Cu2 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 31-35°. In the third S site, S(3) is bonded to three equivalent Nb(1) and two equivalent Cu(1) atoms to form distorted SNb3Cu2 trigonal bipyramids that share corners with two equivalent S(4)Nb5Cu octahedra, corners with five equivalent S(1)Nb3Cu tetrahedra, corners with six equivalent S(2)Nb3Cu2 trigonal bipyramids, edges with three equivalent S(4)Nb5Cu octahedra, edges with two equivalent S(2)Nb3Cu2 trigonal bipyramids, and edges with four equivalent S(3)Nb3Cu2 trigonal bipyramids. The corner-sharing octahedral tilt angles are 39°. In the fourth S site, S(4) is bonded to two equivalent Nb(1), three equivalent Nb(2), and one Cu(1) atom to form distorted SNb5Cu octahedra that share corners with three equivalent S(1)Nb3Cu tetrahedra, corners with two equivalent S(3)Nb3Cu2 trigonal bipyramids, corners with three equivalent S(2)Nb3Cu2 trigonal bipyramids, edges with four equivalent S(4)Nb5Cu octahedra, edges with three equivalent S(1)Nb3Cu tetrahedra, edges with three equivalent S(2)Nb3Cu2 trigonal bipyramids, and edges with three equivalent S(3)Nb3Cu2 trigonal bipyramids.