Hf7As4 crystallizes in the monoclinic C2/m space group. There are eight inequivalent Hf sites. In the first Hf site, Hf(1) is bonded in a distorted square co-planar geometry to two equivalent As(1) and two equivalent As(4) atoms. In the second Hf site, Hf(2) is bonded in a square co-planar geometry to two equivalent As(2) and two equivalent As(3) atoms. In the third Hf site, Hf(3) is bonded in a 4-coordinate geometry to one As(2), two equivalent As(1), and two equivalent As(4) atoms. In the fourth Hf site, Hf(4) is bonded in a 4-coordinate geometry to one As(1), one As(3), and two equivalent As(2) atoms. In the fifth Hf site, Hf(5) is bonded to one As(4), two equivalent As(1), and two equivalent As(3) atoms to form a mixture of distorted face, corner, and edge-sharing HfAs5 trigonal bipyramids. In the sixth Hf site, Hf(6) is bonded in a 5-coordinate geometry to two equivalent As(4) and three equivalent As(1) atoms. In the seventh Hf site, Hf(7) is bonded to one As(4), two equivalent As(2), and two equivalent As(3) atoms to form a mixture of distorted face, corner, and edge-sharing HfAs5 trigonal bipyramids. In the eighth Hf site, Hf(8) is bonded in a 5-coordinate geometry to two equivalent As(3) and three equivalent As(2) atoms. There are four inequivalent As sites. In the first As site, As(3) is bonded in a 8-coordinate geometry to one Hf(2), one Hf(4), two equivalent Hf(5), two equivalent Hf(7), and two equivalent Hf(8) atoms. In the second As site, As(4) is bonded to one Hf(1), one Hf(5), one Hf(7), two equivalent Hf(3), and two equivalent Hf(6) atoms to form a mixture of distorted corner and edge-sharing AsHf7 pentagonal bipyramids. In the third As site, As(1) is bonded in a 9-coordinate geometry to one Hf(1), one Hf(4), two equivalent Hf(3), two equivalent Hf(5), and three equivalent Hf(6) atoms. In the fourth As site, As(2) is bonded in a 9-coordinate geometry to one Hf(2), one Hf(3), two equivalent Hf(4), two equivalent Hf(7), and three equivalent Hf(8) atoms.
Hf7As4 crystallizes in the monoclinic C2/m space group. There are eight inequivalent Hf sites. In the first Hf site, Hf(1) is bonded in a distorted square co-planar geometry to two equivalent As(1) and two equivalent As(4) atoms. Both Hf(1)-As(1) bond lengths are 2.91 Å. Both Hf(1)-As(4) bond lengths are 2.69 Å. In the second Hf site, Hf(2) is bonded in a square co-planar geometry to two equivalent As(2) and two equivalent As(3) atoms. Both Hf(2)-As(2) bond lengths are 2.82 Å. Both Hf(2)-As(3) bond lengths are 2.79 Å. In the third Hf site, Hf(3) is bonded in a 4-coordinate geometry to one As(2), two equivalent As(1), and two equivalent As(4) atoms. The Hf(3)-As(2) bond length is 3.34 Å. Both Hf(3)-As(1) bond lengths are 2.78 Å. Both Hf(3)-As(4) bond lengths are 2.77 Å. In the fourth Hf site, Hf(4) is bonded in a 4-coordinate geometry to one As(1), one As(3), and two equivalent As(2) atoms. The Hf(4)-As(1) bond length is 2.92 Å. The Hf(4)-As(3) bond length is 2.75 Å. Both Hf(4)-As(2) bond lengths are 2.68 Å. In the fifth Hf site, Hf(5) is bonded to one As(4), two equivalent As(1), and two equivalent As(3) atoms to form a mixture of distorted face, corner, and edge-sharing HfAs5 trigonal bipyramids. The Hf(5)-As(4) bond length is 2.65 Å. Both Hf(5)-As(1) bond lengths are 2.74 Å. Both Hf(5)-As(3) bond lengths are 2.78 Å. In the sixth Hf site, Hf(6) is bonded in a 5-coordinate geometry to two equivalent As(4) and three equivalent As(1) atoms. Both Hf(6)-As(4) bond lengths are 2.76 Å. There are two shorter (2.74 Å) and one longer (3.19 Å) Hf(6)-As(1) bond length. In the seventh Hf site, Hf(7) is bonded to one As(4), two equivalent As(2), and two equivalent As(3) atoms to form a mixture of distorted face, corner, and edge-sharing HfAs5 trigonal bipyramids. The Hf(7)-As(4) bond length is 2.71 Å. Both Hf(7)-As(2) bond lengths are 2.75 Å. Both Hf(7)-As(3) bond lengths are 2.75 Å. In the eighth Hf site, Hf(8) is bonded in a 5-coordinate geometry to two equivalent As(3) and three equivalent As(2) atoms. Both Hf(8)-As(3) bond lengths are 2.80 Å. There are two shorter (2.76 Å) and one longer (3.08 Å) Hf(8)-As(2) bond length. There are four inequivalent As sites. In the first As site, As(3) is bonded in a 8-coordinate geometry to one Hf(2), one Hf(4), two equivalent Hf(5), two equivalent Hf(7), and two equivalent Hf(8) atoms. In the second As site, As(4) is bonded to one Hf(1), one Hf(5), one Hf(7), two equivalent Hf(3), and two equivalent Hf(6) atoms to form a mixture of distorted corner and edge-sharing AsHf7 pentagonal bipyramids. In the third As site, As(1) is bonded in a 9-coordinate geometry to one Hf(1), one Hf(4), two equivalent Hf(3), two equivalent Hf(5), and three equivalent Hf(6) atoms. In the fourth As site, As(2) is bonded in a 9-coordinate geometry to one Hf(2), one Hf(3), two equivalent Hf(4), two equivalent Hf(7), and three equivalent Hf(8) atoms.