LaSe2O9 crystallizes in the monoclinic P2_1/c space group. La(1) is bonded in a 9-coordinate geometry to one O(4), one O(5), one O(6), one O(8), one O(9), two equivalent O(2), and two equivalent O(3) atoms. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. In the second Se site, Se(2) is bonded in a tetrahedral geometry to one O(4), one O(5), one O(6), and one O(7) atom. There are nine inequivalent O sites. In the first O site, O(6) is bonded in a bent 150 degrees geometry to one La(1) and one Se(2) atom. In the second O site, O(7) is bonded in a single-bond geometry to one Se(2) atom. In the third O site, O(8) is bonded in a single-bond geometry to one La(1) atom. In the fourth O site, O(1) is bonded in a single-bond geometry to one Se(1) atom. In the fifth O site, O(9) is bonded in a single-bond geometry to one La(1) atom. In the sixth O site, O(2) is bonded in a 3-coordinate geometry to two equivalent La(1) and one Se(1) atom. In the seventh O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent La(1) and one Se(1) atom. In the eighth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one La(1) and one Se(2) atom. In the ninth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one La(1) and one Se(2) atom.
LaSe2O9 crystallizes in the monoclinic P2_1/c space group. La(1) is bonded in a 9-coordinate geometry to one O(4), one O(5), one O(6), one O(8), one O(9), two equivalent O(2), and two equivalent O(3) atoms. The La(1)-O(4) bond length is 2.49 Å. The La(1)-O(5) bond length is 2.40 Å. The La(1)-O(6) bond length is 2.39 Å. The La(1)-O(8) bond length is 2.61 Å. The La(1)-O(9) bond length is 2.66 Å. There is one shorter (2.47 Å) and one longer (2.77 Å) La(1)-O(2) bond length. There is one shorter (2.54 Å) and one longer (2.66 Å) La(1)-O(3) bond length. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. The Se(1)-O(1) bond length is 1.66 Å. The Se(1)-O(2) bond length is 1.73 Å. The Se(1)-O(3) bond length is 1.72 Å. In the second Se site, Se(2) is bonded in a tetrahedral geometry to one O(4), one O(5), one O(6), and one O(7) atom. The Se(2)-O(4) bond length is 1.69 Å. The Se(2)-O(5) bond length is 1.68 Å. The Se(2)-O(6) bond length is 1.68 Å. The Se(2)-O(7) bond length is 1.67 Å. There are nine inequivalent O sites. In the first O site, O(6) is bonded in a bent 150 degrees geometry to one La(1) and one Se(2) atom. In the second O site, O(7) is bonded in a single-bond geometry to one Se(2) atom. In the third O site, O(8) is bonded in a single-bond geometry to one La(1) atom. In the fourth O site, O(1) is bonded in a single-bond geometry to one Se(1) atom. In the fifth O site, O(9) is bonded in a single-bond geometry to one La(1) atom. In the sixth O site, O(2) is bonded in a 3-coordinate geometry to two equivalent La(1) and one Se(1) atom. In the seventh O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent La(1) and one Se(1) atom. In the eighth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one La(1) and one Se(2) atom. In the ninth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one La(1) and one Se(2) atom.