DOE OSTI2020
Eu7Cu44As23 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent Eu+2.43+ sites. In the first Eu+2.43+ site, Eu+2.43+ is bonded in a 8-coordinate geometry to eight As+2.65- atoms. There are four shorter (3.19 Å) and four longer (3.46 Å) Eu–As bond lengths. In the second Eu+2.43+ site, Eu+2.43+ is bonded in a body-centered cubic geometry to eight equivalent As+2.65- atoms. All Eu–As bond lengths are 3.15 Å. There are three inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded to four As+2.65- atoms to form a mixture of edge and corner-sharing CuAs4 tetrahedra. There are three shorter (2.48 Å) and one longer (2.55 Å) Cu–As bond lengths. In the second Cu1+ site, Cu1+ is bonded to four As+2.65- atoms to form a mixture of distorted edge and corner-sharing CuAs4 tetrahedra. There are two shorter (2.45 Å) and two longer (2.51 Å) Cu–As bond lengths. In the third Cu1+ site, Cu1+ is bonded to four As+2.65- atoms to form a mixture of distorted edge and corner-sharing CuAs4 tetrahedra. There are a spread of Cu–As bond distances ranging from 2.52–2.69 Å. There are four inequivalent As+2.65- sites. In the first As+2.65- site, As+2.65- is bonded in a cuboctahedral geometry to twelve equivalent Cu1+ atoms. In the second As+2.65- site, As+2.65- is bonded in a body-centered cubic geometry to eight equivalent Cu1+ atoms. In the third As+2.65- site, As+2.65- is bonded in a 10-coordinate geometry to two equivalent Eu+2.43+ and eight Cu1+ atoms. In the fourth As+2.65- site, As+2.65- is bonded in a 10-coordinate geometry to four Eu+2.43+ and six Cu1+ atoms.