DOE OSTI2020
CaPm3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ca is bonded to twelve Pm atoms to form CaPm12 cuboctahedra that share corners with six equivalent CaPm12 cuboctahedra, corners with twelve PmCa4Pm8 cuboctahedra, edges with eighteen PmCa4Pm8 cuboctahedra, faces with eight equivalent CaPm12 cuboctahedra, and faces with twelve PmCa4Pm8 cuboctahedra. There are six shorter (3.70 Å) and six longer (3.72 Å) Ca–Pm bond lengths. There are two inequivalent Pm sites. In the first Pm site, Pm is bonded to four equivalent Ca and eight equivalent Pm atoms to form PmCa4Pm8 cuboctahedra that share corners with four equivalent CaPm12 cuboctahedra, corners with fourteen equivalent PmCa4Pm8 cuboctahedra, edges with six equivalent CaPm12 cuboctahedra, edges with twelve equivalent PmCa4Pm8 cuboctahedra, faces with four equivalent CaPm12 cuboctahedra, and faces with sixteen PmCa4Pm8 cuboctahedra. There are a spread of Pm–Pm bond distances ranging from 3.66–3.77 Å. In the second Pm site, Pm is bonded to four equivalent Ca and eight equivalent Pm atoms to form PmCa4Pm8 cuboctahedra that share corners with four equivalent CaPm12 cuboctahedra, corners with fourteen PmCa4Pm8 cuboctahedra, edges with six equivalent CaPm12 cuboctahedra, edges with twelve equivalent PmCa4Pm8 cuboctahedra, faces with four equivalent CaPm12 cuboctahedra, and faces with sixteen PmCa4Pm8 cuboctahedra. There are a spread of Pm–Pm bond distances ranging from 3.66–3.77 Å.