Al2PbSe4 crystallizes in the monoclinic Pm space group. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one Se(1), one Se(2), and two equivalent Se(6) atoms to form a mixture of corner and edge-sharing AlSe4 tetrahedra. In the second Al site, Al(2) is bonded to one Se(1), one Se(2), and two equivalent Se(6) atoms to form a mixture of corner and edge-sharing AlSe4 tetrahedra. In the third Al site, Al(3) is bonded to one Se(3), one Se(4), and two equivalent Se(5) atoms to form edge-sharing AlSe4 tetrahedra. In the fourth Al site, Al(4) is bonded to one Se(3), one Se(4), and two equivalent Se(5) atoms to form edge-sharing AlSe4 tetrahedra. Pb(1) is bonded in a 8-coordinate geometry to one Se(1), one Se(2), one Se(3), one Se(4), two equivalent Se(5), and two equivalent Se(6) atoms. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted bent 120 degrees geometry to one Al(1), one Al(2), and two equivalent Pb(1) atoms. In the second Se site, Se(2) is bonded in a distorted bent 120 degrees geometry to one Al(1), one Al(2), and two equivalent Pb(1) atoms. In the third Se site, Se(3) is bonded in a distorted L-shaped geometry to one Al(3), one Al(4), and two equivalent Pb(1) atoms. In the fourth Se site, Se(4) is bonded in a distorted L-shaped geometry to one Al(3), one Al(4), and two equivalent Pb(1) atoms. In the fifth Se site, Se(5) is bonded in a distorted L-shaped geometry to one Al(3), one Al(4), and two equivalent Pb(1) atoms. In the sixth Se site, Se(6) is bonded in a 2-coordinate geometry to one Al(1), one Al(2), and two equivalent Pb(1) atoms.
Al2PbSe4 crystallizes in the monoclinic Pm space group. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one Se(1), one Se(2), and two equivalent Se(6) atoms to form a mixture of corner and edge-sharing AlSe4 tetrahedra. The Al(1)-Se(1) bond length is 2.35 Å. The Al(1)-Se(2) bond length is 2.41 Å. Both Al(1)-Se(6) bond lengths are 2.40 Å. In the second Al site, Al(2) is bonded to one Se(1), one Se(2), and two equivalent Se(6) atoms to form a mixture of corner and edge-sharing AlSe4 tetrahedra. The Al(2)-Se(1) bond length is 2.42 Å. The Al(2)-Se(2) bond length is 2.35 Å. Both Al(2)-Se(6) bond lengths are 2.41 Å. In the third Al site, Al(3) is bonded to one Se(3), one Se(4), and two equivalent Se(5) atoms to form edge-sharing AlSe4 tetrahedra. The Al(3)-Se(3) bond length is 2.43 Å. The Al(3)-Se(4) bond length is 2.39 Å. Both Al(3)-Se(5) bond lengths are 2.41 Å. In the fourth Al site, Al(4) is bonded to one Se(3), one Se(4), and two equivalent Se(5) atoms to form edge-sharing AlSe4 tetrahedra. The Al(4)-Se(3) bond length is 2.40 Å. The Al(4)-Se(4) bond length is 2.42 Å. Both Al(4)-Se(5) bond lengths are 2.41 Å. Pb(1) is bonded in a 8-coordinate geometry to one Se(1), one Se(2), one Se(3), one Se(4), two equivalent Se(5), and two equivalent Se(6) atoms. The Pb(1)-Se(1) bond length is 3.21 Å. The Pb(1)-Se(2) bond length is 3.25 Å. The Pb(1)-Se(3) bond length is 3.21 Å. The Pb(1)-Se(4) bond length is 3.27 Å. There is one shorter (3.22 Å) and one longer (3.29 Å) Pb(1)-Se(5) bond length. There is one shorter (3.15 Å) and one longer (3.41 Å) Pb(1)-Se(6) bond length. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted bent 120 degrees geometry to one Al(1), one Al(2), and two equivalent Pb(1) atoms. In the second Se site, Se(2) is bonded in a distorted bent 120 degrees geometry to one Al(1), one Al(2), and two equivalent Pb(1) atoms. In the third Se site, Se(3) is bonded in a distorted L-shaped geometry to one Al(3), one Al(4), and two equivalent Pb(1) atoms. In the fourth Se site, Se(4) is bonded in a distorted L-shaped geometry to one Al(3), one Al(4), and two equivalent Pb(1) atoms. In the fifth Se site, Se(5) is bonded in a distorted L-shaped geometry to one Al(3), one Al(4), and two equivalent Pb(1) atoms. In the sixth Se site, Se(6) is bonded in a 2-coordinate geometry to one Al(1), one Al(2), and two equivalent Pb(1) atoms.