We present and discuss the results of surface relaxation and rumpling computations for ReO₃, WO₃, SrTiO₃, BaTiO₃ and BaZrO₃ (001) surfaces employing a hybrid B3LYP or B3PW description of exchange and correlation. In particular, we perform the first B3LYP computations for O-terminated ReO₃ and WO₃ (001) surfaces. In most cases, according to our B3LYP or B3PW computations for both surface terminations BO₂- and O, AO-terminated ReO₃, WO₃, BaTiO₃, SrTiO₃ and BaZrO₃ (001) surface upper layer atoms shift downwards, towards the bulk, the second layer atoms shift upwards and the third layer atoms, again, shift downwards. Our ab initio computes that ReO₃, WO₃, BaTiO₃, SrTiO₃ and BaZrO₃ (001) surface Γ-Γ bandgaps are always smaller than their respective bulk Γ-Γ bandgaps. Our first principles compute that B-O atom chemical bond populations in the BaTiO₃, SrTiO₃ and BaZrO₃ perovskite bulk are always smaller than near their BO₂-terminated (001) surfaces. Just opposite, the Re-O and W-O chemical bond populations in the ReO₃ (0.212e) and WO₃ (0.142e) bulk are slightly larger than near the ReO₂ and WO₂-terminated ReO₃ as well as WO₃ (001) surfaces (0.170e and 0.108e, respectively).

Nanocrystalline materials based on titanium dioxide possess unique properties, including photocatalytic and antibacterial activities. Despite many approaches have already been utilized to fabricate and characterize pure and doped TiO₂, a systematic description of its nanostructured samples depending on the synthesis method has not been presented yet. In this study, we shed new light on the process–structure relationships of nanocrystalline TiO₂-based powders fabricated by extraction–pyrolytic, hydrothermal, and sol–gel techniques. The comprehensive analysis of the fabricated nanocrystalline TiO₂-based powders with different anatase/rutile phase content is performed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The hydrothermal and sol–gel methods are also used to grow TiO₂ particles doped with Cu and Er-Yb. The correlation between synthesis parameters (pyrolysis and annealing temperature) and properties of the produced materials is studied. Particular attention is paid to Raman spectroscopy and the detailed comparison of our obtained data with existing experimental and theoretical studies.