CaC2 crystallizes in the trigonal R-3m space group. Ca(1) is bonded to eight equivalent C(1) atoms to form CaC8 hexagonal bipyramids that share corners with eight equivalent C(1)Ca4C trigonal bipyramids and edges with twelve equivalent Ca(1)C8 hexagonal bipyramids. C(1) is bonded to four equivalent Ca(1) and one C(1) atom to form distorted CCa4C trigonal bipyramids that share corners with four equivalent Ca(1)C8 hexagonal bipyramids, corners with sixteen equivalent C(1)Ca4C trigonal bipyramids, and edges with six equivalent C(1)Ca4C trigonal bipyramids.
CaC2 crystallizes in the trigonal R-3m space group. Ca(1) is bonded to eight equivalent C(1) atoms to form CaC8 hexagonal bipyramids that share corners with eight equivalent C(1)Ca4C trigonal bipyramids and edges with twelve equivalent Ca(1)C8 hexagonal bipyramids. There are two shorter (2.59 Å) and six longer (2.84 Å) Ca(1)-C(1) bond lengths. C(1) is bonded to four equivalent Ca(1) and one C(1) atom to form distorted CCa4C trigonal bipyramids that share corners with four equivalent Ca(1)C8 hexagonal bipyramids, corners with sixteen equivalent C(1)Ca4C trigonal bipyramids, and edges with six equivalent C(1)Ca4C trigonal bipyramids. The C(1)-C(1) bond length is 1.27 Å.