DOE OSTI2020
UMnAl is Frank-Kasper $\mu$ Phase-derived structured and crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are five inequivalent U sites. In the first U site, U is bonded in a 12-coordinate geometry to four U, five Mn, and seven Al atoms. There are a spread of U–U bond distances ranging from 3.18–3.37 Å. There are a spread of U–Mn bond distances ranging from 2.90–3.08 Å. There are a spread of U–Al bond distances ranging from 3.09–3.14 Å. In the second U site, U is bonded in a 11-coordinate geometry to four U, seven Mn, and five Al atoms. There are one shorter (2.66 Å) and one longer (3.37 Å) U–U bond lengths. There are a spread of U–Mn bond distances ranging from 2.94–3.11 Å. There are a spread of U–Al bond distances ranging from 3.08–3.17 Å. In the third U site, U is bonded in a 11-coordinate geometry to four U, seven Mn, and five Al atoms. There are two shorter (3.24 Å) and one longer (3.37 Å) U–U bond lengths. There are a spread of U–Mn bond distances ranging from 2.94–3.11 Å. There are a spread of U–Al bond distances ranging from 3.08–3.17 Å. In the fourth U site, U is bonded in a 12-coordinate geometry to four U, five Mn, and seven Al atoms. There are a spread of U–Mn bond distances ranging from 2.90–3.08 Å. There are a spread of U–Al bond distances ranging from 3.09–3.14 Å. In the fifth U site, U is bonded in a 12-coordinate geometry to four U, five Mn, and seven Al atoms. The U–U bond length is 3.18 Å. There are a spread of U–Mn bond distances ranging from 2.90–3.08 Å. There are a spread of U–Al bond distances ranging from 3.09–3.14 Å. There are three inequivalent Mn sites. In the first Mn site, Mn is bonded to six U and six Al atoms to form MnU6Al6 cuboctahedra that share corners with four equivalent AlU6Mn4Al2 cuboctahedra, corners with fourteen MnU6Al6 cuboctahedra, edges with six MnU6Al6 cuboctahedra, faces with four equivalent MnU6Mn4Al2 cuboctahedra, and faces with fourteen AlU6Mn4Al2 cuboctahedra. There are a spread of Mn–Al bond distances ranging from 2.60–2.74 Å. In the second Mn site, Mn is bonded to six U, four Mn, and two equivalent Al atoms to form distorted MnU6Mn4Al2 cuboctahedra that share corners with eight MnU6Al6 cuboctahedra, corners with ten AlU6Mn4Al2 cuboctahedra, edges with two equivalent MnU6Mn4Al2 cuboctahedra, edges with four equivalent AlU6Mn2Al4 cuboctahedra, faces with eight AlU6Mn4Al2 cuboctahedra, and faces with ten MnU6Al6 cuboctahedra. There are a spread of Mn–Mn bond distances ranging from 2.54–2.74 Å. Both Mn–Al bond lengths are 2.52 Å. In the third Mn site, Mn is bonded to six U, four equivalent Mn, and two equivalent Al atoms to form distorted MnU6Mn4Al2 cuboctahedra that share corners with six MnU6Al6 cuboctahedra, corners with twelve AlU6Mn4Al2 cuboctahedra, edges with six MnU6Al6 cuboctahedra, faces with eight equivalent MnU6Mn4Al2 cuboctahedra, and faces with ten AlU6Mn4Al2 cuboctahedra. Both Mn–Al bond lengths are 2.54 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded to six U, four Mn, and two equivalent Al atoms to form distorted AlU6Mn4Al2 cuboctahedra that share corners with four equivalent AlU6Mn2Al4 cuboctahedra, corners with eight MnU6Al6 cuboctahedra, edges with six equivalent AlU6Mn4Al2 cuboctahedra, faces with eight AlU6Mn4Al2 cuboctahedra, and faces with twelve MnU6Al6 cuboctahedra. Both Al–Al bond lengths are 2.64 Å. In the second Al site, Al is bonded to six U, two equivalent Mn, and four Al atoms to form AlU6Mn2Al4 cuboctahedra that share corners with eight AlU6Mn4Al2 cuboctahedra, corners with ten MnU6Mn4Al2 cuboctahedra, edges with two equivalent AlU6Mn2Al4 cuboctahedra, edges with four equivalent MnU6Mn4Al2 cuboctahedra, faces with eight MnU6Al6 cuboctahedra, and faces with ten AlU6Mn4Al2 cuboctahedra. There are one shorter (2.58 Å) and one longer (2.70 Å) Al–Al bond lengths.