Ga3Si crystallizes in the hexagonal P6_3/mmc space group. Ga(1) is bonded to eight equivalent Ga(1) and four equivalent Si(1) atoms to form GaGa8Si4 cuboctahedra that share corners with four equivalent Si(1)Ga12 cuboctahedra, corners with fourteen equivalent Ga(1)Ga8Si4 cuboctahedra, edges with six equivalent Si(1)Ga12 cuboctahedra, edges with twelve equivalent Ga(1)Ga8Si4 cuboctahedra, faces with four equivalent Si(1)Ga12 cuboctahedra, and faces with sixteen equivalent Ga(1)Ga8Si4 cuboctahedra. Si(1) is bonded to twelve equivalent Ga(1) atoms to form SiGa12 cuboctahedra that share corners with six equivalent Si(1)Ga12 cuboctahedra, corners with twelve equivalent Ga(1)Ga8Si4 cuboctahedra, edges with eighteen equivalent Ga(1)Ga8Si4 cuboctahedra, faces with eight equivalent Si(1)Ga12 cuboctahedra, and faces with twelve equivalent Ga(1)Ga8Si4 cuboctahedra.
Ga3Si crystallizes in the hexagonal P6_3/mmc space group. Ga(1) is bonded to eight equivalent Ga(1) and four equivalent Si(1) atoms to form GaGa8Si4 cuboctahedra that share corners with four equivalent Si(1)Ga12 cuboctahedra, corners with fourteen equivalent Ga(1)Ga8Si4 cuboctahedra, edges with six equivalent Si(1)Ga12 cuboctahedra, edges with twelve equivalent Ga(1)Ga8Si4 cuboctahedra, faces with four equivalent Si(1)Ga12 cuboctahedra, and faces with sixteen equivalent Ga(1)Ga8Si4 cuboctahedra. There are a spread of Ga(1)-Ga(1) bond distances ranging from 2.92-3.04 Å. There are two shorter (2.90 Å) and two longer (3.00 Å) Ga(1)-Si(1) bond lengths. Si(1) is bonded to twelve equivalent Ga(1) atoms to form SiGa12 cuboctahedra that share corners with six equivalent Si(1)Ga12 cuboctahedra, corners with twelve equivalent Ga(1)Ga8Si4 cuboctahedra, edges with eighteen equivalent Ga(1)Ga8Si4 cuboctahedra, faces with eight equivalent Si(1)Ga12 cuboctahedra, and faces with twelve equivalent Ga(1)Ga8Si4 cuboctahedra.