Ba3Ac is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. Ba(1) is bonded to eight equivalent Ba(1) and four equivalent Ac(1) atoms to form distorted BaBa8Ac4 cuboctahedra that share corners with four equivalent Ac(1)Ba12 cuboctahedra, corners with fourteen equivalent Ba(1)Ba8Ac4 cuboctahedra, edges with six equivalent Ac(1)Ba12 cuboctahedra, edges with twelve equivalent Ba(1)Ba8Ac4 cuboctahedra, faces with four equivalent Ac(1)Ba12 cuboctahedra, and faces with sixteen equivalent Ba(1)Ba8Ac4 cuboctahedra. Ac(1) is bonded to twelve equivalent Ba(1) atoms to form AcBa12 cuboctahedra that share corners with six equivalent Ac(1)Ba12 cuboctahedra, corners with twelve equivalent Ba(1)Ba8Ac4 cuboctahedra, edges with eighteen equivalent Ba(1)Ba8Ac4 cuboctahedra, faces with eight equivalent Ac(1)Ba12 cuboctahedra, and faces with twelve equivalent Ba(1)Ba8Ac4 cuboctahedra.
Ba3Ac is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. Ba(1) is bonded to eight equivalent Ba(1) and four equivalent Ac(1) atoms to form distorted BaBa8Ac4 cuboctahedra that share corners with four equivalent Ac(1)Ba12 cuboctahedra, corners with fourteen equivalent Ba(1)Ba8Ac4 cuboctahedra, edges with six equivalent Ac(1)Ba12 cuboctahedra, edges with twelve equivalent Ba(1)Ba8Ac4 cuboctahedra, faces with four equivalent Ac(1)Ba12 cuboctahedra, and faces with sixteen equivalent Ba(1)Ba8Ac4 cuboctahedra. There are a spread of Ba(1)-Ba(1) bond distances ranging from 4.26-4.47 Å. There are two shorter (4.25 Å) and two longer (4.36 Å) Ba(1)-Ac(1) bond lengths. Ac(1) is bonded to twelve equivalent Ba(1) atoms to form AcBa12 cuboctahedra that share corners with six equivalent Ac(1)Ba12 cuboctahedra, corners with twelve equivalent Ba(1)Ba8Ac4 cuboctahedra, edges with eighteen equivalent Ba(1)Ba8Ac4 cuboctahedra, faces with eight equivalent Ac(1)Ba12 cuboctahedra, and faces with twelve equivalent Ba(1)Ba8Ac4 cuboctahedra.