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We combined the hybrid density functional theory (DFT) calculations and X-ray absorption spectroscopy (XAS) experiments in the study of the local atomic structure around Ir ions in ZnO thin films with different iridium content. This was then used in the first principles analysis of the thermoelectric properties of material. The emphasis has been put on the conditions for a positive Seebeck coefficient and p-type electrical conductivity as the functions of the Fermi level. We studied both computationally and experimentally several possible IrOx polyhedra (complexes) with a different number of surrounding oxygens and Ir oxidation states, including those with the formation of peroxide ions (O22−). In particular, octahedral coordination of iridium ions was identified by reverse Monte Carlo (RMC) simulations of the Ir L3-edge EXAFS spectra of ZnO:Ir thin films as the predominant complex, which is supported by the calculated lowest interstitial oxygen incorporation energies. All the calculated IrOx (x = 4, 5, 6) complexes, regardless of Ir the oxidation state, demonstrate potential for p-type conduction if the Fermi level (μF) falls in the range of 0–0.8 eV from the valence band maximum (VBM) and the Ir concentration is high enough (12.5% in the present DFT calculations). Even though the corresponding calculated Seebeck coefficient (S) around 80–89 μV K−1 slightly exceeds the experimental values, we emphasise the presence of an important plateau in the dependence of S on μF in this range for two complexes with the formation of peroxide ions (O22−). We predicted also that peroxide ions O22− are characterized by the calculated phonon frequencies of 810–942 cm−1 in agreement with our previous Raman experimental results. In this light, we discuss the high sensitivity of calculated S(μF) dependences to the atomic and electronic structure. [ABSTRACT FROM AUTHOR]

TiO 2 (titania) is one of the promising materials for photocatalytic applications. In this paper we report on recently obtained theoretical results for N and S doped, as well as N+S co-doped 6-layer (101) anatase nanotube (NT). First principles calculations in our study have been performed using a modified B3LYP hybrid exchange-correlation functional within density functional theory (DFT). Here we discuss the energy of defect formation mechanism and electronic band structure for nanotubes under study. We also report on influence of dopant concentration on the NT's band structure and discuss the defect–defect interactions. [ABSTRACT FROM AUTHOR]

An investigation of acoustics in 15 circuses with fabric roofs has been carried out. Objective acoustical parameters (reverberation time, clarity C80, and others) have been measured and questionnaires from the audience in the circuses have been obtained. Features of circuses acoustics are the decrease in reverberation times at low frequencies, echo (in halls with impervious fabric roofs), and high levels of background noise. The background noise levels in circuses before a performance were equal LA=46-56 dBA. The questionnaire contained subjective acoustical attributes: Timbre, balance, reverberance, spaciousness, echo, loudness, clearness, audibility of background noise, background noise affect on speech legibility, and others. Average mark estimates and results of measured noise level in halls (LA) have been subjected to factor analysis. Three factors have been extracted that can be interpreted as (1) overall acoustical impression of the music sound in a circus, (2) disturbing influence of the background noise, and (3) clarity of music and speech sounding. [ABSTRACT FROM AUTHOR]