Valence electron-energy loss spectroscopy (VEELS) in a dedicated scanning transmission electron microscope, vacuum ultraviolet spectroscopy and spectroscopic ellipsometry, and ab initio band structure calculations in the local density approximation have been used to determine the optical properties and the electronic structure of SrTiO3 Assignments of the interband transitions in the electronic structure of bulk SrTiO3 have been determined quantitatively by comparison of VEELS spectra with vacuum ultraviolet spectra and with the ab initio calculated densities of states The experimentally determined indirect band gap energy is 325 eV, while the direct band gap energy is 375 eV The conduction bands in SrTiO3 correspond to the bands composed of mainly Ti 3d t2g and eg states, followed at higher energies by the bands of Sr 4d t2g and eg states, and free electron like states dominating at energies above 15 eV The upper valence band (UVB) contains 18 electrons in dominantly O 2p states, hybridized with Ti and Sr states, and has a bandwidth of 5 eV The interband transitions from the UVB to the Ti 3d bands and to the Sr 4d bands give rise to the transitions spanning from the indirect band gap energy of 325 eV up to 15 eV The lower valence band contains 12 electrons in Sr 4p and O 2s states which are separated by 2 eV, while having a bandwidth of 5 eV The interband transitions from the Sr 4p to the Ti 3d and Sr 4d bands give rise to transition energies spanning from 15 to 24 eV Interband transitions from the O 2s band to the conduction bands appear at 26 eV A very narrow band at −33 eV below the top of the valence band is composed of Sr 4s and Ti 3p states and contains eight electrons

/pdf/bulk-electronic-structure-of-srtio3-experiment-and-theory-1tzugu6bkp.pdf

Bulk electronic structure of SrTiO3: Experiment and theory

Bulk properties and electronic structure of SrTiO3, BaTiO3, PbTiO3 perovskites: an ab initio HF/DFT study

An ab initio pseudopotential method based on density functional theory, generalized gradient corrections to exchange and correlation, and projector-augmented waves is used to investigate structural, energetical, electronic, and optical properties of $\mathrm{MgO}$, $\mathrm{ZnO}$, and $\mathrm{CdO}$ in rocksalt, cesium chloride, zinc blende, and wurtzite structure. In the case of $\mathrm{MgO}$ we also examine the nickel arsenide structure and a graphitic phase. The stability of the ground-state phases rocksalt $(\mathrm{MgO},\mathrm{CdO})$ and wurtzite $(\mathrm{ZnO})$ against hydrostatic pressure and biaxial strain is studied. We also present the band structures of all polymorphs as well as the accompanying dielectric functions. We discuss the physical reasons for the anomalous chemical trend of the ground-state geometry and the fundamental gap with the size of the group-II cation in the oxide. The role of the shallow $\mathrm{Zn}3d$ and $\mathrm{Cd}4d$ electrons is critically examined.

First-principles study of ground- and excited-state properties of MgO , ZnO , and CdO polymorphs

Usually, SrTiO3 monodoped with Cr cations at the Ti4+ site hardly shows visible light photocatalytic activity. Revealing the origin of this issue is important for us to find an alternative approach to make SrTiO3 active under visible light irradiation. In this paper, two Cr-doped SrTiO3(Sr0.95Cr0.05)TiO3 and Sr(Ti0.95Cr0.05)O3were synthesized by a conventional solid-state reaction method, and their photophysical and photocatalytic properties were studied comparatively. It was found that both (Sr0.95Cr0.05)TiO3 and Sr(Ti0.95Cr0.05)O3 showed considerable absorption to visible light. However, their photocatalytic activities for H2 evolution from aqueous methanol solution under visible light irradiation were significantly different:  the H2 evolution rate over (Sr0.95Cr0.05)TiO3 (∼21 μmol/h) was more than 100 times that over Sr(Ti0.95Cr0.05)O3 (∼0.2 μmol/h). X-ray photoelectron spectroscopy analysis results revealed that the Cr cations doped at the Sr2+ site were all trivalent state (Cr3+), while those doped ...

Photophysical and photocatalytic properties of SrTiO3 doped with Cr cations on different sites.

We present a fully variational generalization of the pseudo self-interaction correction (VPSIC) approach previously presented in two implementations based on plane-waves and atomic orbital basis set, known as PSIC and ASIC, respectively. The new method is essentially equivalent to the previous version for what concern the electronic properties, but it can be exploited to calculate total-energy derived properties as well, such as forces and structural optimization. We apply the method to a variety of test cases including both non-magnetic and magnetic correlated oxides and molecules, showing a generally good accuracy in the description of both structural and electronic properties.

Variational pseudo-self-interaction-corrected density functional approach to the ab initio description of correlated solids and molecules

The structural properties and the band structures of the charge-transfer insulating oxides SrO, MgO and SrTiO3 are computed both within density functional theory in the local density approximation (LDA) and in the Hedin's GW scheme for self-energy corrections, by using a model dielectric function, which approximately includes local field and dynamical effects. The deep valence states are shifted by the GW method to higher binding energies, in very good agreement with photoemission spectra. Since in all of these oxides the direct gaps at high-symmetry points of the Brillouin zone may be very sensitive to the actual value of the lattice parameter a, already at the LDA level, self-energy corrections are computed both at the theoretical and the experimental a. For MgO and SrO, the values of the transition energies between the valence and the conduction bands are improved by GW corrections, while for SrTiO3 they are overestimated. The results are discussed in relation to the importance of local field effects and to the nature of the electronic states in these insulating oxides.

G. Cappellini

Papers

Structural properties and quasiparticule energies of cubic SrO, MgO and SrTiO3