CaSi2 is hexagonal omega structure structured and crystallizes in the trigonal P-3m1 space group. Ca(1) is bonded to six equivalent Si(1) atoms to form distorted CaSi6 octahedra that share corners with six equivalent Si(1)Ca3Si3 octahedra, edges with six equivalent Ca(1)Si6 octahedra, and edges with six equivalent Si(1)Ca3Si3 octahedra. The corner-sharing octahedral tilt angles are 22°. Si(1) is bonded to three equivalent Ca(1) and three equivalent Si(1) atoms to form distorted SiCa3Si3 octahedra that share corners with three equivalent Ca(1)Si6 octahedra, corners with three equivalent Si(1)Ca3Si3 octahedra, edges with three equivalent Ca(1)Si6 octahedra, and edges with nine equivalent Si(1)Ca3Si3 octahedra. The corner-sharing octahedral tilt angles range from 0-22°.
CaSi2 is hexagonal omega structure structured and crystallizes in the trigonal P-3m1 space group. Ca(1) is bonded to six equivalent Si(1) atoms to form distorted CaSi6 octahedra that share corners with six equivalent Si(1)Ca3Si3 octahedra, edges with six equivalent Ca(1)Si6 octahedra, and edges with six equivalent Si(1)Ca3Si3 octahedra. The corner-sharing octahedral tilt angles are 22°. All Ca(1)-Si(1) bond lengths are 3.03 Å. Si(1) is bonded to three equivalent Ca(1) and three equivalent Si(1) atoms to form distorted SiCa3Si3 octahedra that share corners with three equivalent Ca(1)Si6 octahedra, corners with three equivalent Si(1)Ca3Si3 octahedra, edges with three equivalent Ca(1)Si6 octahedra, and edges with nine equivalent Si(1)Ca3Si3 octahedra. The corner-sharing octahedral tilt angles range from 0-22°. All Si(1)-Si(1) bond lengths are 2.39 Å.