Y5Si4 crystallizes in the monoclinic P2_1/c space group. There are five inequivalent Y sites. In the first Y site, Y(1) is bonded in a 7-coordinate geometry to one Si(3), two equivalent Si(4), and four equivalent Si(2) atoms. In the second Y site, Y(2) is bonded to one Si(3), two equivalent Si(4), and three equivalent Si(1) atoms to form a mixture of face, corner, and edge-sharing YSi6 octahedra. The corner-sharing octahedral tilt angles range from 41-44°. In the third Y site, Y(3) is bonded in a 6-coordinate geometry to one Si(4), two equivalent Si(3), and three equivalent Si(1) atoms. In the fourth Y site, Y(4) is bonded in a 6-coordinate geometry to one Si(4), two equivalent Si(3), and three equivalent Si(2) atoms. In the fifth Y site, Y(5) is bonded to one Si(1), one Si(2), two equivalent Si(3), and two equivalent Si(4) atoms to form a mixture of distorted face and corner-sharing YSi6 octahedra. The corner-sharing octahedral tilt angles range from 42-56°. There are four inequivalent Si sites. In the first Si site, Si(4) is bonded in a 9-coordinate geometry to one Y(3), one Y(4), two equivalent Y(1), two equivalent Y(2), two equivalent Y(5), and one Si(3) atom. In the second Si site, Si(1) is bonded in a 8-coordinate geometry to one Y(5), three equivalent Y(2), three equivalent Y(3), and one Si(1) atom. In the third Si site, Si(2) is bonded in a 8-coordinate geometry to one Y(5), three equivalent Y(4), and four equivalent Y(1) atoms. In the fourth Si site, Si(3) is bonded in a 9-coordinate geometry to one Y(1), one Y(2), two equivalent Y(3), two equivalent Y(4), two equivalent Y(5), and one Si(4) atom.
Y5Si4 crystallizes in the monoclinic P2_1/c space group. There are five inequivalent Y sites. In the first Y site, Y(1) is bonded in a 7-coordinate geometry to one Si(3), two equivalent Si(4), and four equivalent Si(2) atoms. The Y(1)-Si(3) bond length is 3.16 Å. There is one shorter (3.05 Å) and one longer (3.19 Å) Y(1)-Si(4) bond length. There are a spread of Y(1)-Si(2) bond distances ranging from 2.95-3.55 Å. In the second Y site, Y(2) is bonded to one Si(3), two equivalent Si(4), and three equivalent Si(1) atoms to form a mixture of face, corner, and edge-sharing YSi6 octahedra. The corner-sharing octahedral tilt angles range from 41-44°. The Y(2)-Si(3) bond length is 3.13 Å. There is one shorter (3.03 Å) and one longer (3.10 Å) Y(2)-Si(4) bond length. There are a spread of Y(2)-Si(1) bond distances ranging from 3.05-3.14 Å. In the third Y site, Y(3) is bonded in a 6-coordinate geometry to one Si(4), two equivalent Si(3), and three equivalent Si(1) atoms. The Y(3)-Si(4) bond length is 3.03 Å. There is one shorter (2.91 Å) and one longer (2.95 Å) Y(3)-Si(3) bond length. There are a spread of Y(3)-Si(1) bond distances ranging from 2.86-2.97 Å. In the fourth Y site, Y(4) is bonded in a 6-coordinate geometry to one Si(4), two equivalent Si(3), and three equivalent Si(2) atoms. The Y(4)-Si(4) bond length is 3.00 Å. There is one shorter (2.97 Å) and one longer (3.05 Å) Y(4)-Si(3) bond length. There are a spread of Y(4)-Si(2) bond distances ranging from 2.84-2.96 Å. In the fifth Y site, Y(5) is bonded to one Si(1), one Si(2), two equivalent Si(3), and two equivalent Si(4) atoms to form a mixture of distorted face and corner-sharing YSi6 octahedra. The corner-sharing octahedral tilt angles range from 42-56°. The Y(5)-Si(1) bond length is 3.11 Å. The Y(5)-Si(2) bond length is 2.98 Å. There is one shorter (2.94 Å) and one longer (3.18 Å) Y(5)-Si(3) bond length. There is one shorter (2.95 Å) and one longer (3.06 Å) Y(5)-Si(4) bond length. There are four inequivalent Si sites. In the first Si site, Si(4) is bonded in a 9-coordinate geometry to one Y(3), one Y(4), two equivalent Y(1), two equivalent Y(2), two equivalent Y(5), and one Si(3) atom. The Si(4)-Si(3) bond length is 2.57 Å. In the second Si site, Si(1) is bonded in a 8-coordinate geometry to one Y(5), three equivalent Y(2), three equivalent Y(3), and one Si(1) atom. The Si(1)-Si(1) bond length is 2.42 Å. In the third Si site, Si(2) is bonded in a 8-coordinate geometry to one Y(5), three equivalent Y(4), and four equivalent Y(1) atoms. In the fourth Si site, Si(3) is bonded in a 9-coordinate geometry to one Y(1), one Y(2), two equivalent Y(3), two equivalent Y(4), two equivalent Y(5), and one Si(4) atom.