We completed B3LYP and B3PW computations for AO- and BO₂-terminated (001) as well as AO₃- and B-terminated (111) surfaces of BSO, BTO, STO, PTO, CTO, BZO, SZO, and CZO perovskites. In particular, we performed the first B3LYP computations for polar BSO (111) surfaces. We observed that most of the upper-layer atoms for AO- and BO₂-terminated ABO perovskite (001) surfaces relax inward. In contrast, practically all second-layer atoms relax upward. Lastly, almost all third-layer atoms relax inward. This tendency is less pronounced for atomic relaxation of first, second, and third layer atoms for AO₃- and B-terminated ABO perovskite (111) surfaces. For almost all ABO perovskites, their (001) surface rumplings s are considerably larger for AO-terminated compared to BO₂-terminated surfaces. On the contrary, the ABO perovskite (001) surface energies, for both AO and BO₂-terminations, are essentially equivalent. The ABO perovskite polar (111) surface energies are always substantially larger than their neutral (001) surface energies. In most cases, the surface energies of AO₃-terminated ABO perovskite polar (111) surfaces are considerably larger than their B-terminated surface energies. Our computations illustrate a noticeable boost in the B-O bond covalency near the BO₂-terminated (001) surface related to the bulk. Our computed ABO perovskite bulk Γ-Γ band gaps are almost always reduced near the AO- and BO₂-terminated neutral (001) surfaces as well as in most cases also near the AO₃- and B-terminated polar (111) surfaces.

We employ a simple analytic model to calculate the thermopower of low-transparency molecular nanosystems. It turns out that the sign of the thermovoltage for this model depends sensitively on the participating molecular orbital, and one finds a sign change when the transport channel switches from the highest occupied molecular orbital to the lowest unoccupied molecular orbital. Comparing our results to recent experimental data obtained for a benzenedithiol molecule contacted with a scanning tunneling microscope tip, we observe good agreement.

We employ Green’s function method for describing multiband models with magnetic impurities and apply the formalism to the problem of chromium impurities adsorbed onto a carbon nanotube. Density functional theory is used to determine the bandstructure, which is then fit to a tight-binding model to allow for the subsequent Green’s function description. Electron–electron interactions, electron–phonon coupling, and disorder scattering are all taken into account (perturbatively) with a theory that involves a cluster extension of the coherent potential approximation. We show how increasing the cluster size produces more accurate results and how the final calculations converge as a function of the cluster size. We examine the spin-polarized electrical current on the nanotube generated by the magnetic impurities adsorbed onto the nanotube surface. The spin polarization increases with both increasing concentration of chromium impurities and with increasing magnetic field. Its origin arises from the strong electron correlations generated by the Cr impurities.

In this paper, research has been carried out on the electronic properties of nanostructured graphene. We focus our attention on trapped states of the proposed systems such as spherical and toroidal graphene quantum dots (GQDs). Using a continuum model, by solving the Dirac-Weyl equation, and applying periodic boundary conditions of two types, i.e., either with zigzag edges only or with both armchair and zigzag edges, we obtain analytical results for energy levels yielding self-similar energy bands located subsequently one after another on the energy scale. Only for the toroidal quantum dot (owing to the lack of curvature) the distribution of electron density is like Bohr atomic orbitals. However, although the quasi-zero-energy band exists for both spherical and toroidal quantum dots, no electron density is present on this band for the toroidal quantum dot. This causes the formation of a pseudogap between the hole and electron bands because of the absence of the electron density at the quantum dot center, like in the case of an ordinary atom. Conversely, the confinement of the charge-carrier density is observed for both geometries of GQDs.

The results of most B3LYP and B3PW simulations, performed during the last quarter of century, dealing with ABO perovskite (001) surfaces, heterostructures, and oxygen vacancies therein, were reviewed. According to carried out B3LYP and B3PW simulations, almost all upper-layer atoms on the BO₂- and AO-terminated STO, BTO, PTO, CTO, SZO, BZO, PZO, and CZO perovskite (001) surfaces shift inwards. Practically all ABO perovskite second-layer atoms shift upwards. Finally, nearly all third-layer atoms, once more, shift inwards. The ABO perovskite (001) surface energies, for both BO₂ and AO terminations, are comparable. Computer simulations on the ABO perovskites indicate a significant rise of the B-O chemical bond covalency nearby the BO₂-terminated (001) surfaces in comparison to their bulk. B3LYP- and B3PW-simulated ABO perovskite bulk Γ-Γ band gaps are decreased nearby their BO₂- and AO-terminated (001) surfaces. We discuss recent B3PW simulations for the STO/BTO, STO/PTO, and SZO/PZO (001) heterostructures. Simulated optical band gaps of the STO/BTO, STO/PTO, and SZO/PZO (001) heterostructures mainly depend on the BO₂- or AO-terminations of the upper layer of the augmented film. The displacement magnitudes of the nearest neighbor atoms, around the (001) surface oxygen vacancy, in the ABO perovskites, usually, are larger than in their bulk. In the STO, BTO, PTO, and SZO perovskites, the electronic charge, ordinarily, is a lot better localized inside the bulk than the (001) surface oxygen vacancy. In the STO, BTO, PTO, and SZO perovskites, the (001) surface oxygen vacancy-induced defect levels are located closer to the conduction band bottom than in the bulk cases. Simulated formation energy difference between the bulk and the (001) surface oxygen vacancies in the STO, BTO, PTO, and SZO perovskites triggers the oxygen vacancy segregation from the bulk towards the (001) surface. All computer simulations for ABO perovskites were performed in their high-symmetry cubic phase.