Eu5As4 crystallizes in the orthorhombic Cmce space group. There are two inequivalent Eu sites. In the first Eu site, Eu(1) is bonded to three equivalent As(1) and three equivalent As(2) atoms to form a mixture of distorted corner, edge, and face-sharing EuAs6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 38-43°. In the second Eu site, Eu(2) is bonded to two equivalent As(1) and four equivalent As(2) atoms to form a mixture of corner and face-sharing EuAs6 octahedra. The corner-sharing octahedral tilt angles are 53°. There are two inequivalent As sites. In the first As site, As(1) is bonded to one Eu(2) and six equivalent Eu(1) atoms to form a mixture of distorted corner and edge-sharing AsEu7 pentagonal bipyramids. In the second As site, As(2) is bonded in a 9-coordinate geometry to two equivalent Eu(2), six equivalent Eu(1), and one As(2) atom.
Eu5As4 crystallizes in the orthorhombic Cmce space group. There are two inequivalent Eu sites. In the first Eu site, Eu(1) is bonded to three equivalent As(1) and three equivalent As(2) atoms to form a mixture of distorted corner, edge, and face-sharing EuAs6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 38-43°. There are two shorter (3.09 Å) and one longer (3.15 Å) Eu(1)-As(1) bond length. There are two shorter (3.21 Å) and one longer (3.23 Å) Eu(1)-As(2) bond length. In the second Eu site, Eu(2) is bonded to two equivalent As(1) and four equivalent As(2) atoms to form a mixture of corner and face-sharing EuAs6 octahedra. The corner-sharing octahedral tilt angles are 53°. Both Eu(2)-As(1) bond lengths are 3.08 Å. There are two shorter (3.17 Å) and two longer (3.18 Å) Eu(2)-As(2) bond lengths. There are two inequivalent As sites. In the first As site, As(1) is bonded to one Eu(2) and six equivalent Eu(1) atoms to form a mixture of distorted corner and edge-sharing AsEu7 pentagonal bipyramids. In the second As site, As(2) is bonded in a 9-coordinate geometry to two equivalent Eu(2), six equivalent Eu(1), and one As(2) atom. The As(2)-As(2) bond length is 2.83 Å.