Er3Pr is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to eight Er(1,1) and four equivalent Pr(1) atoms to form ErPr4Er8 cuboctahedra that share corners with four equivalent Pr(1)Er12 cuboctahedra; corners with fourteen equivalent Er(1)Pr4Er8 cuboctahedra; edges with six equivalent Pr(1)Er12 cuboctahedra; edges with twelve Er(1,1)Pr4Er8 cuboctahedra; faces with four equivalent Pr(1)Er12 cuboctahedra; and faces with sixteen Er(1,1)Pr4Er8 cuboctahedra. In the second Er site, Er(1) is bonded to eight equivalent Er(1) and four equivalent Pr(1) atoms to form ErPr4Er8 cuboctahedra that share corners with four equivalent Pr(1)Er12 cuboctahedra; corners with fourteen Er(1,1)Pr4Er8 cuboctahedra; edges with six equivalent Pr(1)Er12 cuboctahedra; edges with twelve equivalent Er(1)Pr4Er8 cuboctahedra; faces with four equivalent Pr(1)Er12 cuboctahedra; and faces with sixteen Er(1,1)Pr4Er8 cuboctahedra. Pr(1) is bonded to twelve Er(1,1) atoms to form PrEr12 cuboctahedra that share corners with six equivalent Pr(1)Er12 cuboctahedra; corners with twelve Er(1,1)Pr4Er8 cuboctahedra; edges with eighteen Er(1,1)Pr4Er8 cuboctahedra; faces with eight equivalent Pr(1)Er12 cuboctahedra; and faces with twelve Er(1,1)Pr4Er8 cuboctahedra.
Er3Pr is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to eight Er(1,1) and four equivalent Pr(1) atoms to form ErPr4Er8 cuboctahedra that share corners with four equivalent Pr(1)Er12 cuboctahedra; corners with fourteen equivalent Er(1)Pr4Er8 cuboctahedra; edges with six equivalent Pr(1)Er12 cuboctahedra; edges with twelve Er(1,1)Pr4Er8 cuboctahedra; faces with four equivalent Pr(1)Er12 cuboctahedra; and faces with sixteen Er(1,1)Pr4Er8 cuboctahedra. There are a spread of Er(1)-Er(1,1) bond distances ranging from 3.53-3.68 Å. There are two shorter (3.56 Å) and two longer (3.63 Å) Er(1)-Pr(1) bond lengths. In the second Er site, Er(1) is bonded to eight equivalent Er(1) and four equivalent Pr(1) atoms to form ErPr4Er8 cuboctahedra that share corners with four equivalent Pr(1)Er12 cuboctahedra; corners with fourteen Er(1,1)Pr4Er8 cuboctahedra; edges with six equivalent Pr(1)Er12 cuboctahedra; edges with twelve equivalent Er(1)Pr4Er8 cuboctahedra; faces with four equivalent Pr(1)Er12 cuboctahedra; and faces with sixteen Er(1,1)Pr4Er8 cuboctahedra. There are two shorter (3.56 Å) and two longer (3.63 Å) Er(1)-Pr(1) bond lengths. Pr(1) is bonded to twelve Er(1,1) atoms to form PrEr12 cuboctahedra that share corners with six equivalent Pr(1)Er12 cuboctahedra; corners with twelve Er(1,1)Pr4Er8 cuboctahedra; edges with eighteen Er(1,1)Pr4Er8 cuboctahedra; faces with eight equivalent Pr(1)Er12 cuboctahedra; and faces with twelve Er(1,1)Pr4Er8 cuboctahedra.