BaAc3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. Ba(1) is bonded to twelve Ac(1,1,1) atoms to form BaAc12 cuboctahedra that share corners with six equivalent Ba(1)Ac12 cuboctahedra; corners with twelve Ac(1,1)Ba4Ac8 cuboctahedra; edges with eighteen Ac(1,1,1)Ba4Ac8 cuboctahedra; faces with eight equivalent Ba(1)Ac12 cuboctahedra; and faces with twelve Ac(1,1,1)Ba4Ac8 cuboctahedra. There are three inequivalent Ac sites. In the first Ac site, Ac(1) is bonded to four equivalent Ba(1) and eight Ac(1,1,1) atoms to form AcBa4Ac8 cuboctahedra that share corners with four equivalent Ba(1)Ac12 cuboctahedra; corners with fourteen Ac(1,1)Ba4Ac8 cuboctahedra; edges with six equivalent Ba(1)Ac12 cuboctahedra; edges with twelve Ac(1,1,1)Ba4Ac8 cuboctahedra; faces with four equivalent Ba(1)Ac12 cuboctahedra; and faces with sixteen Ac(1,1,1)Ba4Ac8 cuboctahedra. In the second Ac site, Ac(1) is bonded to four equivalent Ba(1) and eight equivalent Ac(1) atoms to form AcBa4Ac8 cuboctahedra that share corners with four equivalent Ba(1)Ac12 cuboctahedra; corners with fourteen Ac(1,1)Ba4Ac8 cuboctahedra; edges with six equivalent Ba(1)Ac12 cuboctahedra; edges with twelve equivalent Ac(1)Ba4Ac8 cuboctahedra; faces with four equivalent Ba(1)Ac12 cuboctahedra; and faces with sixteen Ac(1,1,1)Ba4Ac8 cuboctahedra. In the third Ac site, Ac(1) is bonded to four equivalent Ba(1) and eight equivalent Ac(1) atoms to form AcBa4Ac8 cuboctahedra that share corners with four equivalent Ba(1)Ac12 cuboctahedra; corners with fourteen Ac(1,1)Ba4Ac8 cuboctahedra; edges with six equivalent Ba(1)Ac12 cuboctahedra; edges with twelve equivalent Ac(1)Ba4Ac8 cuboctahedra; faces with four equivalent Ba(1)Ac12 cuboctahedra; and faces with sixteen Ac(1,1,1)Ba4Ac8 cuboctahedra.
BaAc3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. Ba(1) is bonded to twelve Ac(1,1,1) atoms to form BaAc12 cuboctahedra that share corners with six equivalent Ba(1)Ac12 cuboctahedra; corners with twelve Ac(1,1)Ba4Ac8 cuboctahedra; edges with eighteen Ac(1,1,1)Ba4Ac8 cuboctahedra; faces with eight equivalent Ba(1)Ac12 cuboctahedra; and faces with twelve Ac(1,1,1)Ba4Ac8 cuboctahedra. There are six shorter (4.10 Å) and six longer (4.12 Å) Ba(1)-Ac(1,1,1) bond lengths. There are three inequivalent Ac sites. In the first Ac site, Ac(1) is bonded to four equivalent Ba(1) and eight Ac(1,1,1) atoms to form AcBa4Ac8 cuboctahedra that share corners with four equivalent Ba(1)Ac12 cuboctahedra; corners with fourteen Ac(1,1)Ba4Ac8 cuboctahedra; edges with six equivalent Ba(1)Ac12 cuboctahedra; edges with twelve Ac(1,1,1)Ba4Ac8 cuboctahedra; faces with four equivalent Ba(1)Ac12 cuboctahedra; and faces with sixteen Ac(1,1,1)Ba4Ac8 cuboctahedra. There are a spread of Ac(1)-Ac(1,1,1) bond distances ranging from 4.00-4.24 Å. In the second Ac site, Ac(1) is bonded to four equivalent Ba(1) and eight equivalent Ac(1) atoms to form AcBa4Ac8 cuboctahedra that share corners with four equivalent Ba(1)Ac12 cuboctahedra; corners with fourteen Ac(1,1)Ba4Ac8 cuboctahedra; edges with six equivalent Ba(1)Ac12 cuboctahedra; edges with twelve equivalent Ac(1)Ba4Ac8 cuboctahedra; faces with four equivalent Ba(1)Ac12 cuboctahedra; and faces with sixteen Ac(1,1,1)Ba4Ac8 cuboctahedra. In the third Ac site, Ac(1) is bonded to four equivalent Ba(1) and eight equivalent Ac(1) atoms to form AcBa4Ac8 cuboctahedra that share corners with four equivalent Ba(1)Ac12 cuboctahedra; corners with fourteen Ac(1,1)Ba4Ac8 cuboctahedra; edges with six equivalent Ba(1)Ac12 cuboctahedra; edges with twelve equivalent Ac(1)Ba4Ac8 cuboctahedra; faces with four equivalent Ba(1)Ac12 cuboctahedra; and faces with sixteen Ac(1,1,1)Ba4Ac8 cuboctahedra.