K3Eu is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. K(1) is bonded to eight equivalent K(1) and four equivalent Eu(1) atoms to form distorted KK8Eu4 cuboctahedra that share corners with four equivalent Eu(1)K12 cuboctahedra, corners with fourteen equivalent K(1)K8Eu4 cuboctahedra, edges with six equivalent Eu(1)K12 cuboctahedra, edges with twelve equivalent K(1)K8Eu4 cuboctahedra, faces with four equivalent Eu(1)K12 cuboctahedra, and faces with sixteen equivalent K(1)K8Eu4 cuboctahedra. Eu(1) is bonded to twelve equivalent K(1) atoms to form EuK12 cuboctahedra that share corners with six equivalent Eu(1)K12 cuboctahedra, corners with twelve equivalent K(1)K8Eu4 cuboctahedra, edges with eighteen equivalent K(1)K8Eu4 cuboctahedra, faces with eight equivalent Eu(1)K12 cuboctahedra, and faces with twelve equivalent K(1)K8Eu4 cuboctahedra.
K3Eu is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. K(1) is bonded to eight equivalent K(1) and four equivalent Eu(1) atoms to form distorted KK8Eu4 cuboctahedra that share corners with four equivalent Eu(1)K12 cuboctahedra, corners with fourteen equivalent K(1)K8Eu4 cuboctahedra, edges with six equivalent Eu(1)K12 cuboctahedra, edges with twelve equivalent K(1)K8Eu4 cuboctahedra, faces with four equivalent Eu(1)K12 cuboctahedra, and faces with sixteen equivalent K(1)K8Eu4 cuboctahedra. There are a spread of K(1)-K(1) bond distances ranging from 4.54-4.63 Å. There are two shorter (4.55 Å) and two longer (4.58 Å) K(1)-Eu(1) bond lengths. Eu(1) is bonded to twelve equivalent K(1) atoms to form EuK12 cuboctahedra that share corners with six equivalent Eu(1)K12 cuboctahedra, corners with twelve equivalent K(1)K8Eu4 cuboctahedra, edges with eighteen equivalent K(1)K8Eu4 cuboctahedra, faces with eight equivalent Eu(1)K12 cuboctahedra, and faces with twelve equivalent K(1)K8Eu4 cuboctahedra.