YNiO3 crystallizes in the hexagonal P6_3cm space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded in a 7-coordinate geometry to one O(1), three equivalent O(3), and three equivalent O(4) atoms. In the second Y site, Y(2) is bonded to one O(2), three equivalent O(3), and three equivalent O(4) atoms to form distorted YO7 pentagonal bipyramids that share corners with three equivalent Ni(1)O5 trigonal bipyramids and edges with three equivalent Ni(1)O5 trigonal bipyramids. Ni(1) is bonded to one O(2), one O(3), one O(4), and two equivalent O(1) atoms to form NiO5 trigonal bipyramids that share  a cornercorner with one Y(2)O7 pentagonal bipyramid, corners with six equivalent Ni(1)O5 trigonal bipyramids, and  an edgeedge with one Y(2)O7 pentagonal bipyramid. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Y(1) and three equivalent Ni(1) atoms to form OYNi3 trigonal pyramids that share corners with six equivalent O(3)Y3Ni tetrahedra, corners with three equivalent O(1)YNi3 trigonal pyramids, corners with three equivalent O(2)YNi3 trigonal pyramids, and edges with three equivalent O(4)Y3Ni tetrahedra. In the second O site, O(2) is bonded to one Y(2) and three equivalent Ni(1) atoms to form OYNi3 trigonal pyramids that share corners with six equivalent O(4)Y3Ni tetrahedra, corners with six equivalent O(1)YNi3 trigonal pyramids, and edges with three equivalent O(3)Y3Ni tetrahedra. In the third O site, O(3) is bonded to one Y(2), two equivalent Y(1), and one Ni(1) atom to form distorted OY3Ni tetrahedra that share corners with four equivalent O(4)Y3Ni tetrahedra, corners with six equivalent O(3)Y3Ni tetrahedra, corners with four equivalent O(1)YNi3 trigonal pyramids, edges with three equivalent O(4)Y3Ni tetrahedra, and  an edgeedge with one O(2)YNi3 trigonal pyramid. In the fourth O site, O(4) is bonded to one Y(2), two equivalent Y(1), and one Ni(1) atom to form OY3Ni tetrahedra that share corners with four equivalent O(3)Y3Ni tetrahedra, corners with six equivalent O(4)Y3Ni tetrahedra, corners with two equivalent O(2)YNi3 trigonal pyramids, edges with three equivalent O(3)Y3Ni tetrahedra, and edges with two equivalent O(1)YNi3 trigonal pyramids.
YNiO3 crystallizes in the hexagonal P6_3cm space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded in a 7-coordinate geometry to one O(1), three equivalent O(3), and three equivalent O(4) atoms. The Y(1)-O(1) bond length is 2.43 Å. All Y(1)-O(3) bond lengths are 2.32 Å. All Y(1)-O(4) bond lengths are 2.28 Å. In the second Y site, Y(2) is bonded to one O(2), three equivalent O(3), and three equivalent O(4) atoms to form distorted YO7 pentagonal bipyramids that share corners with three equivalent Ni(1)O5 trigonal bipyramids and edges with three equivalent Ni(1)O5 trigonal bipyramids. The Y(2)-O(2) bond length is 2.31 Å. All Y(2)-O(3) bond lengths are 2.32 Å. All Y(2)-O(4) bond lengths are 2.30 Å. Ni(1) is bonded to one O(2), one O(3), one O(4), and two equivalent O(1) atoms to form NiO5 trigonal bipyramids that share  a cornercorner with one Y(2)O7 pentagonal bipyramid, corners with six equivalent Ni(1)O5 trigonal bipyramids, and  an edgeedge with one Y(2)O7 pentagonal bipyramid. The Ni(1)-O(2) bond length is 2.07 Å. The Ni(1)-O(3) bond length is 1.86 Å. The Ni(1)-O(4) bond length is 1.86 Å. Both Ni(1)-O(1) bond lengths are 2.07 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Y(1) and three equivalent Ni(1) atoms to form OYNi3 trigonal pyramids that share corners with six equivalent O(3)Y3Ni tetrahedra, corners with three equivalent O(1)YNi3 trigonal pyramids, corners with three equivalent O(2)YNi3 trigonal pyramids, and edges with three equivalent O(4)Y3Ni tetrahedra. In the second O site, O(2) is bonded to one Y(2) and three equivalent Ni(1) atoms to form OYNi3 trigonal pyramids that share corners with six equivalent O(4)Y3Ni tetrahedra, corners with six equivalent O(1)YNi3 trigonal pyramids, and edges with three equivalent O(3)Y3Ni tetrahedra. In the third O site, O(3) is bonded to one Y(2), two equivalent Y(1), and one Ni(1) atom to form distorted OY3Ni tetrahedra that share corners with four equivalent O(4)Y3Ni tetrahedra, corners with six equivalent O(3)Y3Ni tetrahedra, corners with four equivalent O(1)YNi3 trigonal pyramids, edges with three equivalent O(4)Y3Ni tetrahedra, and  an edgeedge with one O(2)YNi3 trigonal pyramid. In the fourth O site, O(4) is bonded to one Y(2), two equivalent Y(1), and one Ni(1) atom to form OY3Ni tetrahedra that share corners with four equivalent O(3)Y3Ni tetrahedra, corners with six equivalent O(4)Y3Ni tetrahedra, corners with two equivalent O(2)YNi3 trigonal pyramids, edges with three equivalent O(3)Y3Ni tetrahedra, and edges with two equivalent O(1)YNi3 trigonal pyramids.