On the basis of neutron diffraction data the Mn−O bond lengths and Mn−O−Mn bond angles for the poly- and nanocrystalline TbMnO3 samples are determined. All the samples crystallize in the orthorhombically distorted perovskite structure (space group Pnma) and exhibit antiferromagnetic ordering below 41 K. The Tb atoms and O1 atoms are in (4)c site, Mn atoms − in 4(b) site and O2 atoms − in 8(d) site. The Mn−O2−Mn bond angles for the polycrystalline and nanosize samples are similar, whereas the Mn−O1−Mn bond angles for the nanoparticle samples are larger. The temperature dependencies of the Mn−O bond lengths and the Mn−O−Mn bond angles, the Jahn-Teller distortion parameter (JT) and MnO6 − octahedron distortion parameter (delta) for polycrystalline sample exhibit anomalies at TN temperature for Mn sublattice.
