MgGa2 crystallizes in the hexagonal P-62m space group. Mg(1) is bonded to three equivalent Mg(1); three equivalent Ga(2); and six Ga(1,1) atoms to form distorted MgMg3Ga9 cuboctahedra that share corners with nine equivalent Mg(1)Mg3Ga9 cuboctahedra; corners with nine equivalent Ga(2)Mg6Ga6 cuboctahedra; edges with six equivalent Mg(1)Mg3Ga9 cuboctahedra; edges with twelve Ga(1,1)Mg4Ga8 cuboctahedra; faces with three equivalent Ga(2)Mg6Ga6 cuboctahedra; faces with five equivalent Mg(1)Mg3Ga9 cuboctahedra; and faces with twelve Ga(1,1)Mg4Ga8 cuboctahedra. There are three inequivalent Ga sites. In the first Ga site, Ga(1) is bonded to four equivalent Mg(1), two equivalent Ga(2), and six equivalent Ga(1) atoms to form distorted GaMg4Ga8 cuboctahedra that share corners with eighteen equivalent Ga(1)Mg4Ga8 cuboctahedra; edges with four equivalent Ga(2)Mg6Ga6 cuboctahedra; edges with six equivalent Ga(1)Mg4Ga8 cuboctahedra; edges with eight equivalent Mg(1)Mg3Ga9 cuboctahedra; faces with four equivalent Ga(2)Mg6Ga6 cuboctahedra; faces with eight equivalent Mg(1)Mg3Ga9 cuboctahedra; and faces with eight Ga(1,1)Mg4Ga8 cuboctahedra. In the second Ga site, Ga(1) is bonded to four equivalent Mg(1); two equivalent Ga(2); and six Ga(1,1) atoms to form distorted GaMg4Ga8 cuboctahedra that share corners with eighteen Ga(1,1)Mg4Ga8 cuboctahedra; edges with four equivalent Ga(2)Mg6Ga6 cuboctahedra; edges with six equivalent Ga(1)Mg4Ga8 cuboctahedra; edges with eight equivalent Mg(1)Mg3Ga9 cuboctahedra; faces with four equivalent Ga(2)Mg6Ga6 cuboctahedra; faces with eight equivalent Mg(1)Mg3Ga9 cuboctahedra; and faces with eight Ga(1,1)Mg4Ga8 cuboctahedra. In the third Ga site, Ga(2) is bonded to six equivalent Mg(1) and six Ga(1,1) atoms to form distorted GaMg6Ga6 cuboctahedra that share corners with eighteen equivalent Mg(1)Mg3Ga9 cuboctahedra; edges with six equivalent Ga(2)Mg6Ga6 cuboctahedra; edges with twelve Ga(1,1)Mg4Ga8 cuboctahedra; faces with two equivalent Ga(2)Mg6Ga6 cuboctahedra; faces with six equivalent Mg(1)Mg3Ga9 cuboctahedra; and faces with twelve Ga(1,1)Mg4Ga8 cuboctahedra.
MgGa2 crystallizes in the hexagonal P-62m space group. Mg(1) is bonded to three equivalent Mg(1); three equivalent Ga(2); and six Ga(1,1) atoms to form distorted MgMg3Ga9 cuboctahedra that share corners with nine equivalent Mg(1)Mg3Ga9 cuboctahedra; corners with nine equivalent Ga(2)Mg6Ga6 cuboctahedra; edges with six equivalent Mg(1)Mg3Ga9 cuboctahedra; edges with twelve Ga(1,1)Mg4Ga8 cuboctahedra; faces with three equivalent Ga(2)Mg6Ga6 cuboctahedra; faces with five equivalent Mg(1)Mg3Ga9 cuboctahedra; and faces with twelve Ga(1,1)Mg4Ga8 cuboctahedra. All Mg(1)-Mg(1) bond lengths are 2.98 Å. All Mg(1)-Ga(2) bond lengths are 2.98 Å. All Mg(1)-Ga(1,1) bond lengths are 2.95 Å. There are three inequivalent Ga sites. In the first Ga site, Ga(1) is bonded to four equivalent Mg(1), two equivalent Ga(2), and six equivalent Ga(1) atoms to form distorted GaMg4Ga8 cuboctahedra that share corners with eighteen equivalent Ga(1)Mg4Ga8 cuboctahedra; edges with four equivalent Ga(2)Mg6Ga6 cuboctahedra; edges with six equivalent Ga(1)Mg4Ga8 cuboctahedra; edges with eight equivalent Mg(1)Mg3Ga9 cuboctahedra; faces with four equivalent Ga(2)Mg6Ga6 cuboctahedra; faces with eight equivalent Mg(1)Mg3Ga9 cuboctahedra; and faces with eight Ga(1,1)Mg4Ga8 cuboctahedra. Both Ga(1)-Ga(2) bond lengths are 2.96 Å. There are four shorter (2.98 Å) and two longer (2.99 Å) Ga(1)-Ga(1) bond lengths. In the second Ga site, Ga(1) is bonded to four equivalent Mg(1); two equivalent Ga(2); and six Ga(1,1) atoms to form distorted GaMg4Ga8 cuboctahedra that share corners with eighteen Ga(1,1)Mg4Ga8 cuboctahedra; edges with four equivalent Ga(2)Mg6Ga6 cuboctahedra; edges with six equivalent Ga(1)Mg4Ga8 cuboctahedra; edges with eight equivalent Mg(1)Mg3Ga9 cuboctahedra; faces with four equivalent Ga(2)Mg6Ga6 cuboctahedra; faces with eight equivalent Mg(1)Mg3Ga9 cuboctahedra; and faces with eight Ga(1,1)Mg4Ga8 cuboctahedra. Both Ga(1)-Ga(2) bond lengths are 2.96 Å. There are two shorter (2.98 Å) and one longer (2.99 Å) Ga(1)-Ga(1) bond length. In the third Ga site, Ga(2) is bonded to six equivalent Mg(1) and six Ga(1,1) atoms to form distorted GaMg6Ga6 cuboctahedra that share corners with eighteen equivalent Mg(1)Mg3Ga9 cuboctahedra; edges with six equivalent Ga(2)Mg6Ga6 cuboctahedra; edges with twelve Ga(1,1)Mg4Ga8 cuboctahedra; faces with two equivalent Ga(2)Mg6Ga6 cuboctahedra; faces with six equivalent Mg(1)Mg3Ga9 cuboctahedra; and faces with twelve Ga(1,1)Mg4Ga8 cuboctahedra.