Nd2Ta2O9 crystallizes in the monoclinic P2_1/c space group. Nd(1) is bonded in a 9-coordinate geometry to one O(4), two equivalent O(1), three equivalent O(2), and three equivalent O(5) atoms. Ta(1) is bonded to one O(3), one O(5), two equivalent O(1), and two equivalent O(4) atoms to form a mixture of distorted corner and edge-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles range from 0-14°. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Nd(1) and two equivalent Ta(1) atoms to form a mixture of distorted corner and edge-sharing ONd2Ta2 trigonal pyramids. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to three equivalent Nd(1) atoms. In the third O site, O(3) is bonded in a linear geometry to two equivalent Ta(1) atoms. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Nd(1) and two equivalent Ta(1) atoms. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to three equivalent Nd(1) and one Ta(1) atom.
Nd2Ta2O9 crystallizes in the monoclinic P2_1/c space group. Nd(1) is bonded in a 9-coordinate geometry to one O(4), two equivalent O(1), three equivalent O(2), and three equivalent O(5) atoms. The Nd(1)-O(4) bond length is 2.56 Å. There is one shorter (2.59 Å) and one longer (2.60 Å) Nd(1)-O(1) bond length. There are a spread of Nd(1)-O(2) bond distances ranging from 2.40-2.61 Å. There is one shorter (2.37 Å) and two longer (2.58 Å) Nd(1)-O(5) bond lengths. Ta(1) is bonded to one O(3), one O(5), two equivalent O(1), and two equivalent O(4) atoms to form a mixture of distorted corner and edge-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles range from 0-14°. The Ta(1)-O(3) bond length is 1.91 Å. The Ta(1)-O(5) bond length is 1.98 Å. There is one shorter (1.97 Å) and one longer (2.20 Å) Ta(1)-O(1) bond length. There is one shorter (1.96 Å) and one longer (1.97 Å) Ta(1)-O(4) bond length. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Nd(1) and two equivalent Ta(1) atoms to form a mixture of distorted corner and edge-sharing ONd2Ta2 trigonal pyramids. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to three equivalent Nd(1) atoms. In the third O site, O(3) is bonded in a linear geometry to two equivalent Ta(1) atoms. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Nd(1) and two equivalent Ta(1) atoms. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to three equivalent Nd(1) and one Ta(1) atom.