Er(PO3)3 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one O(1), one O(2), two equivalent O(4), and two equivalent O(7) atoms to form ErO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and corners with two equivalent P(3)O4 tetrahedra. In the second Er site, Er(2) is bonded to one O(10), one O(11), two equivalent O(5), and two equivalent O(8) atoms to form ErO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra, and corners with two equivalent P(4)O4 tetrahedra. There are four inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form PO4 tetrahedra that share corners with two equivalent Er(1)O6 octahedra and corners with two equivalent P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 10-40°. In the second P site, P(2) is bonded to one O(3), one O(4), one O(5), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one Er(1)O6 octahedra,  a cornercorner with one Er(2)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and  a cornercorner with one P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 25-29°. In the third P site, P(3) is bonded to one O(6), one O(7), one O(8), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Er(1)O6 octahedra,  a cornercorner with one Er(2)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, and  a cornercorner with one P(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 26-39°. In the fourth P site, P(4) is bonded to one O(10), one O(11), and two equivalent O(9) atoms to form PO4 tetrahedra that share corners with two equivalent Er(2)O6 octahedra and corners with two equivalent P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 10-41°. There are eleven inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Er(1) and one P(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Er(1) and one P(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fourth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Er(2) and one P(4) atom. In the fifth O site, O(4) is bonded in a bent 150 degrees geometry to one Er(1) and one P(2) atom. In the sixth O site, O(11) is bonded in a linear geometry to one Er(2) and one P(4) atom. In the seventh O site, O(5) is bonded in a bent 150 degrees geometry to one Er(2) and one P(2) atom. In the eighth O site, O(6) is bonded in a bent 120 degrees geometry to one P(2) and one P(3) atom. In the ninth O site, O(7) is bonded in a bent 150 degrees geometry to one Er(1) and one P(3) atom. In the tenth O site, O(8) is bonded in a bent 150 degrees geometry to one Er(2) and one P(3) atom. In the eleventh O site, O(9) is bonded in a bent 150 degrees geometry to one P(3) and one P(4) atom.
Er(PO3)3 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one O(1), one O(2), two equivalent O(4), and two equivalent O(7) atoms to form ErO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and corners with two equivalent P(3)O4 tetrahedra. The Er(1)-O(1) bond length is 2.25 Å. The Er(1)-O(2) bond length is 2.21 Å. Both Er(1)-O(4) bond lengths are 2.19 Å. Both Er(1)-O(7) bond lengths are 2.21 Å. In the second Er site, Er(2) is bonded to one O(10), one O(11), two equivalent O(5), and two equivalent O(8) atoms to form ErO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra, and corners with two equivalent P(4)O4 tetrahedra. The Er(2)-O(10) bond length is 2.23 Å. The Er(2)-O(11) bond length is 2.22 Å. Both Er(2)-O(5) bond lengths are 2.20 Å. Both Er(2)-O(8) bond lengths are 2.20 Å. There are four inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form PO4 tetrahedra that share corners with two equivalent Er(1)O6 octahedra and corners with two equivalent P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 10-40°. The P(1)-O(1) bond length is 1.49 Å. The P(1)-O(2) bond length is 1.49 Å. Both P(1)-O(3) bond lengths are 1.59 Å. In the second P site, P(2) is bonded to one O(3), one O(4), one O(5), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one Er(1)O6 octahedra,  a cornercorner with one Er(2)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and  a cornercorner with one P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 25-29°. The P(2)-O(3) bond length is 1.58 Å. The P(2)-O(4) bond length is 1.48 Å. The P(2)-O(5) bond length is 1.48 Å. The P(2)-O(6) bond length is 1.60 Å. In the third P site, P(3) is bonded to one O(6), one O(7), one O(8), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Er(1)O6 octahedra,  a cornercorner with one Er(2)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, and  a cornercorner with one P(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 26-39°. The P(3)-O(6) bond length is 1.60 Å. The P(3)-O(7) bond length is 1.48 Å. The P(3)-O(8) bond length is 1.49 Å. The P(3)-O(9) bond length is 1.58 Å. In the fourth P site, P(4) is bonded to one O(10), one O(11), and two equivalent O(9) atoms to form PO4 tetrahedra that share corners with two equivalent Er(2)O6 octahedra and corners with two equivalent P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 10-41°. The P(4)-O(10) bond length is 1.48 Å. The P(4)-O(11) bond length is 1.49 Å. Both P(4)-O(9) bond lengths are 1.59 Å. There are eleven inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Er(1) and one P(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Er(1) and one P(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fourth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Er(2) and one P(4) atom. In the fifth O site, O(4) is bonded in a bent 150 degrees geometry to one Er(1) and one P(2) atom. In the sixth O site, O(11) is bonded in a linear geometry to one Er(2) and one P(4) atom. In the seventh O site, O(5) is bonded in a bent 150 degrees geometry to one Er(2) and one P(2) atom. In the eighth O site, O(6) is bonded in a bent 120 degrees geometry to one P(2) and one P(3) atom. In the ninth O site, O(7) is bonded in a bent 150 degrees geometry to one Er(1) and one P(3) atom. In the tenth O site, O(8) is bonded in a bent 150 degrees geometry to one Er(2) and one P(3) atom. In the eleventh O site, O(9) is bonded in a bent 150 degrees geometry to one P(3) and one P(4) atom.