DOE OSTI2020
EuAu4Al8Si crystallizes in the tetragonal P4mm space group. The structure is three-dimensional. Eu is bonded in a 8-coordinate geometry to four equivalent Au, eight Al, and four equivalent Si atoms. All Eu–Au bond lengths are 3.33 Å. There are four shorter (3.42 Å) and four longer (3.52 Å) Eu–Al bond lengths. All Eu–Si bond lengths are 3.23 Å. There are four inequivalent Au sites. In the first Au site, Au is bonded in a body-centered cubic geometry to eight Al atoms. All Au–Al bond lengths are 2.62 Å. In the second Au site, Au is bonded in a body-centered cubic geometry to eight Al atoms. There are four shorter (2.61 Å) and four longer (2.65 Å) Au–Al bond lengths. In the third Au site, Au is bonded in a body-centered cubic geometry to eight Al atoms. There are four shorter (2.59 Å) and four longer (2.64 Å) Au–Al bond lengths. In the fourth Au site, Au is bonded in a 9-coordinate geometry to four equivalent Eu, four equivalent Al, and one Si atom. All Au–Al bond lengths are 2.58 Å. The Au–Si bond length is 2.47 Å. There are four inequivalent Al sites. In the first Al site, Al is bonded to two equivalent Eu and four Au atoms to form a mixture of face, edge, and corner-sharing AlEu2Au4 tetrahedra. In the second Al site, Al is bonded to two equivalent Eu, two equivalent Au, and two equivalent Si atoms to form distorted AlEu2Si2Au2 tetrahedra that share corners with fourteen AlEu2Au4 tetrahedra, edges with four AlEu2Au4 tetrahedra, and faces with four equivalent AlEu2Si2Au2 tetrahedra. Both Al–Si bond lengths are 2.65 Å. In the third Al site, Al is bonded to four Au atoms to form a mixture of edge and corner-sharing AlAu4 tetrahedra. In the fourth Al site, Al is bonded to four Au atoms to form a mixture of edge and corner-sharing AlAu4 tetrahedra. Si is bonded in a 1-coordinate geometry to four equivalent Eu, one Au, and four equivalent Al atoms.