Nb4As3 crystallizes in the orthorhombic Cmcm space group. There are five inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one As(1), one As(4), two equivalent As(2), and two equivalent As(3) atoms to form distorted NbAs6 octahedra that share corners with two equivalent Nb(1)As6 octahedra, corners with four equivalent Nb(5)As6 octahedra, corners with five equivalent Nb(2)As5 square pyramids, corners with two equivalent Nb(3)As5 trigonal bipyramids, edges with two equivalent Nb(1)As6 octahedra, edges with three equivalent Nb(3)As5 trigonal bipyramids,  a faceface with one Nb(1)As6 octahedra,  a faceface with one Nb(5)As6 octahedra, and  a faceface with one Nb(2)As5 square pyramid. The corner-sharing octahedral tilt angles range from 44-53°. In the second Nb site, Nb(2) is bonded to one As(4), two equivalent As(1), and two equivalent As(2) atoms to form distorted NbAs5 square pyramids that share corners with five equivalent Nb(1)As6 octahedra,  a cornercorner with one Nb(2)As5 square pyramid, corners with six equivalent Nb(3)As5 trigonal bipyramids, edges with two equivalent Nb(5)As6 octahedra, edges with two equivalent Nb(2)As5 square pyramids, edges with two equivalent Nb(3)As5 trigonal bipyramids, and  a faceface with one Nb(1)As6 octahedra. The corner-sharing octahedral tilt angles range from 36-54°. In the third Nb site, Nb(3) is bonded to two equivalent As(1) and three equivalent As(2) atoms to form distorted NbAs5 trigonal bipyramids that share corners with two equivalent Nb(1)As6 octahedra, corners with two equivalent Nb(5)As6 octahedra, corners with six equivalent Nb(2)As5 square pyramids, edges with three equivalent Nb(1)As6 octahedra, edges with two equivalent Nb(2)As5 square pyramids, and edges with four equivalent Nb(3)As5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 33-44°. In the fourth Nb site, Nb(4) is bonded in a distorted square co-planar geometry to two equivalent As(1) and two equivalent As(2) atoms. In the fifth Nb site, Nb(5) is bonded to two equivalent As(1), two equivalent As(3), and two equivalent As(4) atoms to form distorted NbAs6 octahedra that share corners with eight equivalent Nb(1)As6 octahedra, corners with four equivalent Nb(3)As5 trigonal bipyramids, edges with two equivalent Nb(5)As6 octahedra, edges with four equivalent Nb(2)As5 square pyramids, and faces with two equivalent Nb(1)As6 octahedra. The corner-sharing octahedral tilt angles range from 44-53°. There are four inequivalent As sites. In the first As site, As(1) is bonded in a 7-coordinate geometry to one Nb(1), one Nb(4), one Nb(5), two equivalent Nb(2), and two equivalent Nb(3) atoms. In the second As site, As(2) is bonded in a 8-coordinate geometry to one Nb(4), two equivalent Nb(1), two equivalent Nb(2), and three equivalent Nb(3) atoms. In the third As site, As(3) is bonded to two equivalent Nb(5) and four equivalent Nb(1) atoms to form distorted face-sharing AsNb6 pentagonal pyramids. In the fourth As site, As(4) is bonded in a 6-coordinate geometry to two equivalent Nb(1), two equivalent Nb(2), and two equivalent Nb(5) atoms.
Nb4As3 crystallizes in the orthorhombic Cmcm space group. There are five inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one As(1), one As(4), two equivalent As(2), and two equivalent As(3) atoms to form distorted NbAs6 octahedra that share corners with two equivalent Nb(1)As6 octahedra, corners with four equivalent Nb(5)As6 octahedra, corners with five equivalent Nb(2)As5 square pyramids, corners with two equivalent Nb(3)As5 trigonal bipyramids, edges with two equivalent Nb(1)As6 octahedra, edges with three equivalent Nb(3)As5 trigonal bipyramids,  a faceface with one Nb(1)As6 octahedra,  a faceface with one Nb(5)As6 octahedra, and  a faceface with one Nb(2)As5 square pyramid. The corner-sharing octahedral tilt angles range from 44-53°. The Nb(1)-As(1) bond length is 2.55 Å. The Nb(1)-As(4) bond length is 2.83 Å. Both Nb(1)-As(2) bond lengths are 2.63 Å. Both Nb(1)-As(3) bond lengths are 2.66 Å. In the second Nb site, Nb(2) is bonded to one As(4), two equivalent As(1), and two equivalent As(2) atoms to form distorted NbAs5 square pyramids that share corners with five equivalent Nb(1)As6 octahedra,  a cornercorner with one Nb(2)As5 square pyramid, corners with six equivalent Nb(3)As5 trigonal bipyramids, edges with two equivalent Nb(5)As6 octahedra, edges with two equivalent Nb(2)As5 square pyramids, edges with two equivalent Nb(3)As5 trigonal bipyramids, and  a faceface with one Nb(1)As6 octahedra. The corner-sharing octahedral tilt angles range from 36-54°. The Nb(2)-As(4) bond length is 2.58 Å. Both Nb(2)-As(1) bond lengths are 2.64 Å. Both Nb(2)-As(2) bond lengths are 2.66 Å. In the third Nb site, Nb(3) is bonded to two equivalent As(1) and three equivalent As(2) atoms to form distorted NbAs5 trigonal bipyramids that share corners with two equivalent Nb(1)As6 octahedra, corners with two equivalent Nb(5)As6 octahedra, corners with six equivalent Nb(2)As5 square pyramids, edges with three equivalent Nb(1)As6 octahedra, edges with two equivalent Nb(2)As5 square pyramids, and edges with four equivalent Nb(3)As5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 33-44°. Both Nb(3)-As(1) bond lengths are 2.68 Å. There are two shorter (2.67 Å) and one longer (2.73 Å) Nb(3)-As(2) bond length. In the fourth Nb site, Nb(4) is bonded in a distorted square co-planar geometry to two equivalent As(1) and two equivalent As(2) atoms. Both Nb(4)-As(1) bond lengths are 2.65 Å. Both Nb(4)-As(2) bond lengths are 2.73 Å. In the fifth Nb site, Nb(5) is bonded to two equivalent As(1), two equivalent As(3), and two equivalent As(4) atoms to form distorted NbAs6 octahedra that share corners with eight equivalent Nb(1)As6 octahedra, corners with four equivalent Nb(3)As5 trigonal bipyramids, edges with two equivalent Nb(5)As6 octahedra, edges with four equivalent Nb(2)As5 square pyramids, and faces with two equivalent Nb(1)As6 octahedra. The corner-sharing octahedral tilt angles range from 44-53°. Both Nb(5)-As(1) bond lengths are 2.59 Å. Both Nb(5)-As(3) bond lengths are 2.72 Å. Both Nb(5)-As(4) bond lengths are 2.73 Å. There are four inequivalent As sites. In the first As site, As(1) is bonded in a 7-coordinate geometry to one Nb(1), one Nb(4), one Nb(5), two equivalent Nb(2), and two equivalent Nb(3) atoms. In the second As site, As(2) is bonded in a 8-coordinate geometry to one Nb(4), two equivalent Nb(1), two equivalent Nb(2), and three equivalent Nb(3) atoms. In the third As site, As(3) is bonded to two equivalent Nb(5) and four equivalent Nb(1) atoms to form distorted face-sharing AsNb6 pentagonal pyramids. In the fourth As site, As(4) is bonded in a 6-coordinate geometry to two equivalent Nb(1), two equivalent Nb(2), and two equivalent Nb(5) atoms.