Vibrational and electronic peculiarities of NiTiO3 nanostructures inferred from first principle calculations

Abstract

Structural, electronic and vibrational properties of nanostructured (NiTiO₃)_n clusters were calculated by numerical models based on DFT and semi-empirical quantum chemistry codes. The clusters were built by using the initial atomic positions of crystalline ilmenite, which were relaxed to ensure stable and energetically favourable geometries. For the electronic properties, the semi-empirical PM6 parameterisation method was used to evaluate the HOMO–LUMO energy differences versus nanocrystal sizes. The quantum confinement effect was induced with cluster size reduction. Theoretical UV-Vis absorption and Raman spectroscopy showed the drastic influence of the surface characteristics on the electronic and the vibrational properties of the nanoclusters. Theoretically, it was proved that powder NiTiO₃ exhibits a patchwork of the properties of the bulk ilmenite material, amorphous Ni–Ti–O structures and atoms located at the surface of the investigated cluster.