DOE OSTI2020
Mg7Nd4Ge6 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are four inequivalent Mg sites. In the first Mg site, Mg is bonded to four Ge atoms to form distorted MgGe4 tetrahedra that share corners with four equivalent NdGe6 octahedra, corners with six MgGe4 tetrahedra, edges with two equivalent NdGe6 octahedra, and edges with four MgGe4 tetrahedra. The corner-sharing octahedra tilt angles range from 12–58°. There are one shorter (2.69 Å) and three longer (2.88 Å) Mg–Ge bond lengths. In the second Mg site, Mg is bonded to four Ge atoms to form distorted MgGe4 tetrahedra that share corners with two equivalent NdGe6 octahedra, corners with eight MgGe4 tetrahedra, edges with two equivalent NdGe6 octahedra, and edges with two MgGe4 tetrahedra. The corner-sharing octahedral tilt angles are 46°. There are a spread of Mg–Ge bond distances ranging from 2.75–2.81 Å. In the third Mg site, Mg is bonded to four Ge atoms to form distorted MgGe4 tetrahedra that share corners with three equivalent NdGe6 octahedra, corners with eight MgGe4 tetrahedra, edges with three equivalent NdGe6 octahedra, and edges with two equivalent MgGe4 tetrahedra. The corner-sharing octahedra tilt angles range from 16–63°. There are a spread of Mg–Ge bond distances ranging from 2.62–2.94 Å. In the fourth Mg site, Mg is bonded in a distorted square co-planar geometry to four equivalent Ge atoms. All Mg–Ge bond lengths are 2.92 Å. There are two inequivalent Nd sites. In the first Nd site, Nd is bonded in a 5-coordinate geometry to five Ge atoms. There are a spread of Nd–Ge bond distances ranging from 3.11–3.20 Å. In the second Nd site, Nd is bonded to six Ge atoms to form distorted NdGe6 octahedra that share corners with nine MgGe4 tetrahedra, edges with four equivalent NdGe6 octahedra, and edges with seven MgGe4 tetrahedra. There are a spread of Nd–Ge bond distances ranging from 3.09–3.38 Å. There are three inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to five Mg and four Nd atoms. In the second Ge site, Ge is bonded in a 7-coordinate geometry to four Mg and three equivalent Nd atoms. In the third Ge site, Ge is bonded in a 9-coordinate geometry to five Mg and four Nd atoms.