Mg2Ga crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(2), four equivalent Mg(1), and six equivalent Ga(1) atoms to form distorted MgMg6Ga6 cuboctahedra that share corners with six equivalent Mg(1)Mg6Ga6 cuboctahedra, corners with six equivalent Mg(2)Mg8Ga4 cuboctahedra, corners with twelve equivalent Ga(1)Mg10 cuboctahedra,  an edgeedge with one Ga(1)Mg10 cuboctahedra, edges with eleven equivalent Mg(2)Mg8Ga4 cuboctahedra, faces with four equivalent Mg(2)Mg8Ga4 cuboctahedra, faces with six equivalent Ga(1)Mg10 cuboctahedra, and faces with ten equivalent Mg(1)Mg6Ga6 cuboctahedra. In the second Mg site, Mg(2) is bonded to two equivalent Mg(1), six equivalent Mg(2), and four equivalent Ga(1) atoms to form distorted MgMg8Ga4 cuboctahedra that share corners with six equivalent Mg(1)Mg6Ga6 cuboctahedra, corners with six equivalent Mg(2)Mg8Ga4 cuboctahedra, corners with eight equivalent Ga(1)Mg10 cuboctahedra,  an edgeedge with one Ga(1)Mg10 cuboctahedra, edges with four equivalent Mg(2)Mg8Ga4 cuboctahedra, edges with eleven equivalent Mg(1)Mg6Ga6 cuboctahedra, faces with four equivalent Mg(1)Mg6Ga6 cuboctahedra, faces with eight equivalent Mg(2)Mg8Ga4 cuboctahedra, and faces with eight equivalent Ga(1)Mg10 cuboctahedra. Ga(1) is bonded to four equivalent Mg(2) and six equivalent Mg(1) atoms to form distorted GaMg10 cuboctahedra that share corners with four equivalent Ga(1)Mg10 cuboctahedra, corners with eight equivalent Mg(2)Mg8Ga4 cuboctahedra, corners with twelve equivalent Mg(1)Mg6Ga6 cuboctahedra,  an edgeedge with one Mg(1)Mg6Ga6 cuboctahedra,  an edgeedge with one Mg(2)Mg8Ga4 cuboctahedra, edges with eight equivalent Ga(1)Mg10 cuboctahedra, faces with six equivalent Mg(1)Mg6Ga6 cuboctahedra, faces with six equivalent Ga(1)Mg10 cuboctahedra, and faces with eight equivalent Mg(2)Mg8Ga4 cuboctahedra.
Mg2Ga crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(2), four equivalent Mg(1), and six equivalent Ga(1) atoms to form distorted MgMg6Ga6 cuboctahedra that share corners with six equivalent Mg(1)Mg6Ga6 cuboctahedra, corners with six equivalent Mg(2)Mg8Ga4 cuboctahedra, corners with twelve equivalent Ga(1)Mg10 cuboctahedra,  an edgeedge with one Ga(1)Mg10 cuboctahedra, edges with eleven equivalent Mg(2)Mg8Ga4 cuboctahedra, faces with four equivalent Mg(2)Mg8Ga4 cuboctahedra, faces with six equivalent Ga(1)Mg10 cuboctahedra, and faces with ten equivalent Mg(1)Mg6Ga6 cuboctahedra. Both Mg(1)-Mg(2) bond lengths are 3.09 Å. There are two shorter (3.05 Å) and two longer (3.08 Å) Mg(1)-Mg(1) bond lengths. There are four shorter (3.06 Å) and two longer (3.08 Å) Mg(1)-Ga(1) bond lengths. In the second Mg site, Mg(2) is bonded to two equivalent Mg(1), six equivalent Mg(2), and four equivalent Ga(1) atoms to form distorted MgMg8Ga4 cuboctahedra that share corners with six equivalent Mg(1)Mg6Ga6 cuboctahedra, corners with six equivalent Mg(2)Mg8Ga4 cuboctahedra, corners with eight equivalent Ga(1)Mg10 cuboctahedra,  an edgeedge with one Ga(1)Mg10 cuboctahedra, edges with four equivalent Mg(2)Mg8Ga4 cuboctahedra, edges with eleven equivalent Mg(1)Mg6Ga6 cuboctahedra, faces with four equivalent Mg(1)Mg6Ga6 cuboctahedra, faces with eight equivalent Mg(2)Mg8Ga4 cuboctahedra, and faces with eight equivalent Ga(1)Mg10 cuboctahedra. There are four shorter (3.05 Å) and two longer (3.08 Å) Mg(2)-Mg(2) bond lengths. All Mg(2)-Ga(1) bond lengths are 3.06 Å. Ga(1) is bonded to four equivalent Mg(2) and six equivalent Mg(1) atoms to form distorted GaMg10 cuboctahedra that share corners with four equivalent Ga(1)Mg10 cuboctahedra, corners with eight equivalent Mg(2)Mg8Ga4 cuboctahedra, corners with twelve equivalent Mg(1)Mg6Ga6 cuboctahedra,  an edgeedge with one Mg(1)Mg6Ga6 cuboctahedra,  an edgeedge with one Mg(2)Mg8Ga4 cuboctahedra, edges with eight equivalent Ga(1)Mg10 cuboctahedra, faces with six equivalent Mg(1)Mg6Ga6 cuboctahedra, faces with six equivalent Ga(1)Mg10 cuboctahedra, and faces with eight equivalent Mg(2)Mg8Ga4 cuboctahedra.