Y4C7 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Y sites. In the first Y site, Y(1) is bonded to one C(3), two equivalent C(1), and three equivalent C(7) atoms to form distorted YC6 octahedra that share corners with two equivalent Y(4)C7 octahedra, edges with three equivalent Y(4)C7 octahedra, and edges with four equivalent Y(1)C6 octahedra. The corner-sharing octahedral tilt angles range from 2-3°. In the second Y site, Y(2) is bonded in a 8-coordinate geometry to one C(3), one C(6), two equivalent C(2), two equivalent C(4), and two equivalent C(5) atoms. In the third Y site, Y(3) is bonded in a 9-coordinate geometry to one C(1), one C(5), one C(7), two equivalent C(3), two equivalent C(4), and two equivalent C(6) atoms. In the fourth Y site, Y(4) is bonded to one C(1), one C(4), one C(5), two equivalent C(2), and two equivalent C(7) atoms to form distorted YC7 octahedra that share corners with two equivalent Y(1)C6 octahedra,  a cornercorner with one C(2)Y4C trigonal bipyramid,  a cornercorner with one C(3)Y4C trigonal bipyramid, edges with two equivalent Y(4)C7 octahedra, and edges with three equivalent Y(1)C6 octahedra. The corner-sharing octahedral tilt angles range from 2-3°. There are seven inequivalent C sites. In the first C site, C(5) is bonded in a 6-coordinate geometry to one Y(3), one Y(4), two equivalent Y(2), one C(2), and one C(3) atom. In the second C site, C(6) is bonded in a 4-coordinate geometry to one Y(2), two equivalent Y(3), one C(1), and one C(4) atom. In the third C site, C(7) is bonded to one Y(3), two equivalent Y(4), and three equivalent Y(1) atoms to form CY6 octahedra that share  a cornercorner with one C(3)Y4C trigonal bipyramid, corners with two equivalent C(2)Y4C trigonal bipyramids, edges with two equivalent C(4)Y5C octahedra, edges with four equivalent C(7)Y6 octahedra,  an edgeedge with one C(2)Y4C trigonal bipyramid, and edges with two equivalent C(3)Y4C trigonal bipyramids. In the fourth C site, C(1) is bonded in a 5-coordinate geometry to one Y(3), one Y(4), two equivalent Y(1), and one C(6) atom. In the fifth C site, C(2) is bonded to two equivalent Y(2), two equivalent Y(4), and one C(5) atom to form distorted CY4C trigonal bipyramids that share  a cornercorner with one Y(4)C7 octahedra, corners with two equivalent C(4)Y5C octahedra, corners with two equivalent C(7)Y6 octahedra, corners with two equivalent C(2)Y4C trigonal bipyramids, corners with three equivalent C(3)Y4C trigonal bipyramids,  an edgeedge with one C(7)Y6 octahedra, edges with two equivalent C(4)Y5C octahedra, and  an edgeedge with one C(2)Y4C trigonal bipyramid. The corner-sharing octahedral tilt angles range from 9-116°. In the sixth C site, C(3) is bonded to one Y(1), one Y(2), two equivalent Y(3), and one C(5) atom to form distorted CY4C trigonal bipyramids that share  a cornercorner with one Y(4)C7 octahedra,  a cornercorner with one C(7)Y6 octahedra, corners with four equivalent C(4)Y5C octahedra, corners with two equivalent C(3)Y4C trigonal bipyramids, corners with three equivalent C(2)Y4C trigonal bipyramids,  an edgeedge with one C(4)Y5C octahedra, and edges with two equivalent C(7)Y6 octahedra. The corner-sharing octahedral tilt angles range from 2-95°. In the seventh C site, C(4) is bonded to one Y(4), two equivalent Y(2), two equivalent Y(3), and one C(6) atom to form distorted CY5C octahedra that share corners with two equivalent C(2)Y4C trigonal bipyramids, corners with four equivalent C(3)Y4C trigonal bipyramids, edges with two equivalent C(4)Y5C octahedra, edges with two equivalent C(7)Y6 octahedra,  an edgeedge with one C(3)Y4C trigonal bipyramid, and edges with two equivalent C(2)Y4C trigonal bipyramids.
Y4C7 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Y sites. In the first Y site, Y(1) is bonded to one C(3), two equivalent C(1), and three equivalent C(7) atoms to form distorted YC6 octahedra that share corners with two equivalent Y(4)C7 octahedra, edges with three equivalent Y(4)C7 octahedra, and edges with four equivalent Y(1)C6 octahedra. The corner-sharing octahedral tilt angles range from 2-3°. The Y(1)-C(3) bond length is 2.55 Å. There is one shorter (2.59 Å) and one longer (2.62 Å) Y(1)-C(1) bond length. There are a spread of Y(1)-C(7) bond distances ranging from 2.50-2.67 Å. In the second Y site, Y(2) is bonded in a 8-coordinate geometry to one C(3), one C(6), two equivalent C(2), two equivalent C(4), and two equivalent C(5) atoms. The Y(2)-C(3) bond length is 2.51 Å. The Y(2)-C(6) bond length is 2.58 Å. There is one shorter (2.44 Å) and one longer (2.60 Å) Y(2)-C(2) bond length. There is one shorter (2.48 Å) and one longer (2.58 Å) Y(2)-C(4) bond length. There is one shorter (2.54 Å) and one longer (2.68 Å) Y(2)-C(5) bond length. In the third Y site, Y(3) is bonded in a 9-coordinate geometry to one C(1), one C(5), one C(7), two equivalent C(3), two equivalent C(4), and two equivalent C(6) atoms. The Y(3)-C(1) bond length is 2.72 Å. The Y(3)-C(5) bond length is 2.71 Å. The Y(3)-C(7) bond length is 2.40 Å. There is one shorter (2.45 Å) and one longer (2.50 Å) Y(3)-C(3) bond length. There is one shorter (2.52 Å) and one longer (2.73 Å) Y(3)-C(4) bond length. There is one shorter (2.51 Å) and one longer (2.93 Å) Y(3)-C(6) bond length. In the fourth Y site, Y(4) is bonded to one C(1), one C(4), one C(5), two equivalent C(2), and two equivalent C(7) atoms to form distorted YC7 octahedra that share corners with two equivalent Y(1)C6 octahedra,  a cornercorner with one C(2)Y4C trigonal bipyramid,  a cornercorner with one C(3)Y4C trigonal bipyramid, edges with two equivalent Y(4)C7 octahedra, and edges with three equivalent Y(1)C6 octahedra. The corner-sharing octahedral tilt angles range from 2-3°. The Y(4)-C(1) bond length is 2.59 Å. The Y(4)-C(4) bond length is 2.47 Å. The Y(4)-C(5) bond length is 3.06 Å. There is one shorter (2.69 Å) and one longer (2.76 Å) Y(4)-C(2) bond length. There is one shorter (2.51 Å) and one longer (2.54 Å) Y(4)-C(7) bond length. There are seven inequivalent C sites. In the first C site, C(5) is bonded in a 6-coordinate geometry to one Y(3), one Y(4), two equivalent Y(2), one C(2), and one C(3) atom. The C(5)-C(2) bond length is 1.32 Å. The C(5)-C(3) bond length is 1.32 Å. In the second C site, C(6) is bonded in a 4-coordinate geometry to one Y(2), two equivalent Y(3), one C(1), and one C(4) atom. The C(6)-C(1) bond length is 1.31 Å. The C(6)-C(4) bond length is 1.34 Å. In the third C site, C(7) is bonded to one Y(3), two equivalent Y(4), and three equivalent Y(1) atoms to form CY6 octahedra that share  a cornercorner with one C(3)Y4C trigonal bipyramid, corners with two equivalent C(2)Y4C trigonal bipyramids, edges with two equivalent C(4)Y5C octahedra, edges with four equivalent C(7)Y6 octahedra,  an edgeedge with one C(2)Y4C trigonal bipyramid, and edges with two equivalent C(3)Y4C trigonal bipyramids. In the fourth C site, C(1) is bonded in a 5-coordinate geometry to one Y(3), one Y(4), two equivalent Y(1), and one C(6) atom. In the fifth C site, C(2) is bonded to two equivalent Y(2), two equivalent Y(4), and one C(5) atom to form distorted CY4C trigonal bipyramids that share  a cornercorner with one Y(4)C7 octahedra, corners with two equivalent C(4)Y5C octahedra, corners with two equivalent C(7)Y6 octahedra, corners with two equivalent C(2)Y4C trigonal bipyramids, corners with three equivalent C(3)Y4C trigonal bipyramids,  an edgeedge with one C(7)Y6 octahedra, edges with two equivalent C(4)Y5C octahedra, and  an edgeedge with one C(2)Y4C trigonal bipyramid. The corner-sharing octahedral tilt angles range from 9-116°. In the sixth C site, C(3) is bonded to one Y(1), one Y(2), two equivalent Y(3), and one C(5) atom to form distorted CY4C trigonal bipyramids that share  a cornercorner with one Y(4)C7 octahedra,  a cornercorner with one C(7)Y6 octahedra, corners with four equivalent C(4)Y5C octahedra, corners with two equivalent C(3)Y4C trigonal bipyramids, corners with three equivalent C(2)Y4C trigonal bipyramids,  an edgeedge with one C(4)Y5C octahedra, and edges with two equivalent C(7)Y6 octahedra. The corner-sharing octahedral tilt angles range from 2-95°. In the seventh C site, C(4) is bonded to one Y(4), two equivalent Y(2), two equivalent Y(3), and one C(6) atom to form distorted CY5C octahedra that share corners with two equivalent C(2)Y4C trigonal bipyramids, corners with four equivalent C(3)Y4C trigonal bipyramids, edges with two equivalent C(4)Y5C octahedra, edges with two equivalent C(7)Y6 octahedra,  an edgeedge with one C(3)Y4C trigonal bipyramid, and edges with two equivalent C(2)Y4C trigonal bipyramids.