Eu2SiO5 crystallizes in the monoclinic C2/c space group. There are two inequivalent Eu sites. In the first Eu site, Eu(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(5) atoms to form distorted EuO6 octahedra that share corners with four equivalent Si(1)O4 tetrahedra and edges with two equivalent Eu(1)O6 octahedra. In the second Eu site, Eu(2) is bonded in a 7-coordinate geometry to one O(3), two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with four equivalent Eu(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-68°. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Eu(1) and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Eu(2) and one Si(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Eu(1), one Eu(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Eu(1), two equivalent Eu(2), and one Si(1) atom. In the fifth O site, O(5) is bonded to two equivalent Eu(1) and two equivalent Eu(2) atoms to form edge-sharing OEu4 tetrahedra.
Eu2SiO5 crystallizes in the monoclinic C2/c space group. There are two inequivalent Eu sites. In the first Eu site, Eu(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(5) atoms to form distorted EuO6 octahedra that share corners with four equivalent Si(1)O4 tetrahedra and edges with two equivalent Eu(1)O6 octahedra. The Eu(1)-O(3) bond length is 2.34 Å. The Eu(1)-O(4) bond length is 2.36 Å. There is one shorter (2.35 Å) and one longer (2.38 Å) Eu(1)-O(1) bond length. There is one shorter (2.30 Å) and one longer (2.36 Å) Eu(1)-O(5) bond length. In the second Eu site, Eu(2) is bonded in a 7-coordinate geometry to one O(3), two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms. The Eu(2)-O(3) bond length is 2.41 Å. There is one shorter (2.40 Å) and one longer (2.41 Å) Eu(2)-O(2) bond length. There is one shorter (2.45 Å) and one longer (2.72 Å) Eu(2)-O(4) bond length. There is one shorter (2.32 Å) and one longer (2.46 Å) Eu(2)-O(5) bond length. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with four equivalent Eu(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-68°. The Si(1)-O(1) bond length is 1.65 Å. The Si(1)-O(2) bond length is 1.64 Å. The Si(1)-O(3) bond length is 1.64 Å. The Si(1)-O(4) bond length is 1.66 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Eu(1) and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Eu(2) and one Si(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Eu(1), one Eu(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Eu(1), two equivalent Eu(2), and one Si(1) atom. In the fifth O site, O(5) is bonded to two equivalent Eu(1) and two equivalent Eu(2) atoms to form edge-sharing OEu4 tetrahedra.