Mg2MnAs2 crystallizes in the trigonal P3m1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to three equivalent As(1) and three equivalent As(2) atoms to form MgAs6 octahedra that share corners with six equivalent Mg(2)As4 tetrahedra, corners with six equivalent Mn(1)As4 tetrahedra, edges with six equivalent Mg(1)As6 octahedra, edges with three equivalent Mg(2)As4 tetrahedra, and edges with three equivalent Mn(1)As4 tetrahedra. In the second Mg site, Mg(2) is bonded to one As(1) and three equivalent As(2) atoms to form distorted MgAs4 tetrahedra that share corners with six equivalent Mg(1)As6 octahedra, corners with six equivalent Mg(2)As4 tetrahedra, edges with three equivalent Mg(1)As6 octahedra, and edges with three equivalent Mn(1)As4 tetrahedra. The corner-sharing octahedral tilt angles range from 13-57°. Mn(1) is bonded to one As(2) and three equivalent As(1) atoms to form distorted MnAs4 tetrahedra that share corners with six equivalent Mg(1)As6 octahedra, corners with six equivalent Mn(1)As4 tetrahedra, edges with three equivalent Mg(1)As6 octahedra, and edges with three equivalent Mg(2)As4 tetrahedra. The corner-sharing octahedral tilt angles range from 13-57°. There are two inequivalent As sites. In the first As site, As(1) is bonded to one Mg(2), three equivalent Mg(1), and three equivalent Mn(1) atoms to form distorted AsMg4Mn3 pentagonal bipyramids that share corners with three equivalent As(2)Mg6Mn pentagonal bipyramids, edges with six equivalent As(1)Mg4Mn3 pentagonal bipyramids, and edges with six equivalent As(2)Mg6Mn pentagonal bipyramids. In the second As site, As(2) is bonded to three equivalent Mg(1), three equivalent Mg(2), and one Mn(1) atom to form distorted AsMg6Mn pentagonal bipyramids that share corners with three equivalent As(1)Mg4Mn3 pentagonal bipyramids, edges with six equivalent As(1)Mg4Mn3 pentagonal bipyramids, and edges with six equivalent As(2)Mg6Mn pentagonal bipyramids.
Mg2MnAs2 crystallizes in the trigonal P3m1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to three equivalent As(1) and three equivalent As(2) atoms to form MgAs6 octahedra that share corners with six equivalent Mg(2)As4 tetrahedra, corners with six equivalent Mn(1)As4 tetrahedra, edges with six equivalent Mg(1)As6 octahedra, edges with three equivalent Mg(2)As4 tetrahedra, and edges with three equivalent Mn(1)As4 tetrahedra. All Mg(1)-As(1) bond lengths are 2.90 Å. All Mg(1)-As(2) bond lengths are 2.91 Å. In the second Mg site, Mg(2) is bonded to one As(1) and three equivalent As(2) atoms to form distorted MgAs4 tetrahedra that share corners with six equivalent Mg(1)As6 octahedra, corners with six equivalent Mg(2)As4 tetrahedra, edges with three equivalent Mg(1)As6 octahedra, and edges with three equivalent Mn(1)As4 tetrahedra. The corner-sharing octahedral tilt angles range from 13-57°. The Mg(2)-As(1) bond length is 2.70 Å. All Mg(2)-As(2) bond lengths are 2.60 Å. Mn(1) is bonded to one As(2) and three equivalent As(1) atoms to form distorted MnAs4 tetrahedra that share corners with six equivalent Mg(1)As6 octahedra, corners with six equivalent Mn(1)As4 tetrahedra, edges with three equivalent Mg(1)As6 octahedra, and edges with three equivalent Mg(2)As4 tetrahedra. The corner-sharing octahedral tilt angles range from 13-57°. The Mn(1)-As(2) bond length is 2.70 Å. All Mn(1)-As(1) bond lengths are 2.60 Å. There are two inequivalent As sites. In the first As site, As(1) is bonded to one Mg(2), three equivalent Mg(1), and three equivalent Mn(1) atoms to form distorted AsMg4Mn3 pentagonal bipyramids that share corners with three equivalent As(2)Mg6Mn pentagonal bipyramids, edges with six equivalent As(1)Mg4Mn3 pentagonal bipyramids, and edges with six equivalent As(2)Mg6Mn pentagonal bipyramids. In the second As site, As(2) is bonded to three equivalent Mg(1), three equivalent Mg(2), and one Mn(1) atom to form distorted AsMg6Mn pentagonal bipyramids that share corners with three equivalent As(1)Mg4Mn3 pentagonal bipyramids, edges with six equivalent As(1)Mg4Mn3 pentagonal bipyramids, and edges with six equivalent As(2)Mg6Mn pentagonal bipyramids.