Mg6MoSi crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 3-coordinate geometry to two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mo(1), and one Si(1) atom. In the second Mg site, Mg(2) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Si(1) atoms to form distorted MgMg10Si2 cuboctahedra that share corners with six equivalent Mg(2)Mg10Si2 cuboctahedra, edges with four equivalent Mg(4)Mg10Mo2 cuboctahedra, faces with two equivalent Mg(4)Mg10Mo2 cuboctahedra, faces with two equivalent Mg(2)Mg10Si2 cuboctahedra, and faces with six equivalent Mo(1)Mg10Si2 cuboctahedra. In the third Mg site, Mg(3) is bonded in a 12-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mo(1), and two equivalent Si(1) atoms. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Mo(1) atoms to form distorted MgMg10Mo2 cuboctahedra that share corners with four equivalent Mo(1)Mg10Si2 cuboctahedra, corners with six equivalent Mg(4)Mg10Mo2 cuboctahedra, edges with two equivalent Mo(1)Mg10Si2 cuboctahedra, edges with four equivalent Mg(2)Mg10Si2 cuboctahedra, faces with two equivalent Mg(4)Mg10Mo2 cuboctahedra, faces with two equivalent Mg(2)Mg10Si2 cuboctahedra, and faces with two equivalent Mo(1)Mg10Si2 cuboctahedra. Mo(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Si(1) atoms to form MoMg10Si2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Mo2 cuboctahedra, corners with six equivalent Mo(1)Mg10Si2 cuboctahedra, edges with two equivalent Mg(4)Mg10Mo2 cuboctahedra, faces with two equivalent Mg(4)Mg10Mo2 cuboctahedra, faces with two equivalent Mo(1)Mg10Si2 cuboctahedra, and faces with six equivalent Mg(2)Mg10Si2 cuboctahedra. Si(1) is bonded in a 10-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), four equivalent Mg(3), and two equivalent Mo(1) atoms.
Mg6MoSi crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 3-coordinate geometry to two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mo(1), and one Si(1) atom. There is one shorter (3.03 Å) and one longer (3.04 Å) Mg(1)-Mg(2) bond length. Both Mg(1)-Mg(3) bond lengths are 2.98 Å. Both Mg(1)-Mg(4) bond lengths are 2.99 Å. Both Mg(1)-Mo(1) bond lengths are 2.96 Å. The Mg(1)-Si(1) bond length is 2.76 Å. In the second Mg site, Mg(2) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Si(1) atoms to form distorted MgMg10Si2 cuboctahedra that share corners with six equivalent Mg(2)Mg10Si2 cuboctahedra, edges with four equivalent Mg(4)Mg10Mo2 cuboctahedra, faces with two equivalent Mg(4)Mg10Mo2 cuboctahedra, faces with two equivalent Mg(2)Mg10Si2 cuboctahedra, and faces with six equivalent Mo(1)Mg10Si2 cuboctahedra. Both Mg(2)-Mg(4) bond lengths are 2.96 Å. All Mg(2)-Mg(3) bond lengths are 2.98 Å. Both Mg(2)-Si(1) bond lengths are 3.07 Å. In the third Mg site, Mg(3) is bonded in a 12-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mo(1), and two equivalent Si(1) atoms. There is one shorter (3.01 Å) and one longer (3.11 Å) Mg(3)-Mg(3) bond length. There is one shorter (3.02 Å) and one longer (3.06 Å) Mg(3)-Mg(4) bond length. There is one shorter (2.92 Å) and one longer (3.15 Å) Mg(3)-Mo(1) bond length. Both Mg(3)-Si(1) bond lengths are 3.04 Å. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Mo(1) atoms to form distorted MgMg10Mo2 cuboctahedra that share corners with four equivalent Mo(1)Mg10Si2 cuboctahedra, corners with six equivalent Mg(4)Mg10Mo2 cuboctahedra, edges with two equivalent Mo(1)Mg10Si2 cuboctahedra, edges with four equivalent Mg(2)Mg10Si2 cuboctahedra, faces with two equivalent Mg(4)Mg10Mo2 cuboctahedra, faces with two equivalent Mg(2)Mg10Si2 cuboctahedra, and faces with two equivalent Mo(1)Mg10Si2 cuboctahedra. Both Mg(4)-Mo(1) bond lengths are 3.06 Å. Mo(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Si(1) atoms to form MoMg10Si2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Mo2 cuboctahedra, corners with six equivalent Mo(1)Mg10Si2 cuboctahedra, edges with two equivalent Mg(4)Mg10Mo2 cuboctahedra, faces with two equivalent Mg(4)Mg10Mo2 cuboctahedra, faces with two equivalent Mo(1)Mg10Si2 cuboctahedra, and faces with six equivalent Mg(2)Mg10Si2 cuboctahedra. Both Mo(1)-Si(1) bond lengths are 2.76 Å. Si(1) is bonded in a 10-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), four equivalent Mg(3), and two equivalent Mo(1) atoms.