Y2SiO5 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded in a 8-coordinate geometry to one O(1), two equivalent O(3), two equivalent O(4), and three equivalent O(5) atoms. In the second Y site, Y(2) is bonded to one O(3), three equivalent O(1), and three equivalent O(2) atoms to form distorted YO7 hexagonal pyramids that share corners with two equivalent Si(1)O4 tetrahedra, edges with six equivalent Y(2)O7 hexagonal pyramids, and  an edgeedge with one Si(1)O4 tetrahedra. Si(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form SiO4 tetrahedra that share corners with two equivalent Y(2)O7 hexagonal pyramids and  an edgeedge with one Y(2)O7 hexagonal pyramid. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Y(1) and three equivalent Y(2) atoms to form a mixture of corner and edge-sharing OY4 tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to three equivalent Y(2) and one Si(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Y(2), two equivalent Y(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Y(1) and one Si(1) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to three equivalent Y(1) and one Si(1) atom.
Y2SiO5 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded in a 8-coordinate geometry to one O(1), two equivalent O(3), two equivalent O(4), and three equivalent O(5) atoms. The Y(1)-O(1) bond length is 2.28 Å. There is one shorter (2.24 Å) and one longer (2.47 Å) Y(1)-O(3) bond length. There is one shorter (2.34 Å) and one longer (2.47 Å) Y(1)-O(4) bond length. There are a spread of Y(1)-O(5) bond distances ranging from 2.31-2.64 Å. In the second Y site, Y(2) is bonded to one O(3), three equivalent O(1), and three equivalent O(2) atoms to form distorted YO7 hexagonal pyramids that share corners with two equivalent Si(1)O4 tetrahedra, edges with six equivalent Y(2)O7 hexagonal pyramids, and  an edgeedge with one Si(1)O4 tetrahedra. The Y(2)-O(3) bond length is 2.34 Å. There are a spread of Y(2)-O(1) bond distances ranging from 2.22-2.31 Å. There are a spread of Y(2)-O(2) bond distances ranging from 2.35-2.51 Å. Si(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form SiO4 tetrahedra that share corners with two equivalent Y(2)O7 hexagonal pyramids and  an edgeedge with one Y(2)O7 hexagonal pyramid. The Si(1)-O(2) bond length is 1.65 Å. The Si(1)-O(3) bond length is 1.65 Å. The Si(1)-O(4) bond length is 1.59 Å. The Si(1)-O(5) bond length is 1.62 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Y(1) and three equivalent Y(2) atoms to form a mixture of corner and edge-sharing OY4 tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to three equivalent Y(2) and one Si(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Y(2), two equivalent Y(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Y(1) and one Si(1) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to three equivalent Y(1) and one Si(1) atom.