DOE OSTI2020
U2Fe12P7 crystallizes in the hexagonal P-6 space group. The structure is three-dimensional. there are two inequivalent U sites. In the first U site, U is bonded in a 12-coordinate geometry to six equivalent Fe and six equivalent P atoms. All U–Fe bond lengths are 2.90 Å. All U–P bond lengths are 2.90 Å. In the second U site, U is bonded to six equivalent Fe and six equivalent P atoms to form distorted UFe6P6 cuboctahedra that share corners with twelve FeP4 tetrahedra, edges with three equivalent FeU2P4 tetrahedra, and faces with two equivalent UFe6P6 cuboctahedra. All U–Fe bond lengths are 2.87 Å. All U–P bond lengths are 2.88 Å. There are four inequivalent Fe sites. In the first Fe site, Fe is bonded to four P atoms to form distorted FeP4 tetrahedra that share corners with two equivalent UFe6P6 cuboctahedra, corners with six FeP4 tetrahedra, and edges with two equivalent FeU2P4 tetrahedra. There are a spread of Fe–P bond distances ranging from 2.15–2.25 Å. In the second Fe site, Fe is bonded to two equivalent U and four P atoms to form distorted FeU2P4 tetrahedra that share corners with two equivalent UFe6P6 cuboctahedra, corners with six FeP4 tetrahedra, an edgeedge with one UFe6P6 cuboctahedra, edges with four FeP4 tetrahedra, and faces with two equivalent FeU2P4 tetrahedra. There are a spread of Fe–P bond distances ranging from 2.23–2.30 Å. In the third Fe site, Fe is bonded in a 4-coordinate geometry to two equivalent U and four P atoms. There are a spread of Fe–P bond distances ranging from 2.23–2.32 Å. In the fourth Fe site, Fe is bonded in a 5-coordinate geometry to five P atoms. There are a spread of Fe–P bond distances ranging from 2.24–2.54 Å. There are three inequivalent P sites. In the first P site, P is bonded in a 9-coordinate geometry to two equivalent U and seven Fe atoms. In the second P site, P is bonded in a 3-coordinate geometry to nine Fe atoms. In the third P site, P is bonded in a 9-coordinate geometry to two equivalent U and seven Fe atoms.