Theoretical calculations of hydrogen adsorption by SnO2 (110) surface: Effect of doping and calcination

A pseudopotential plane-wave based density functional theory simulations of the hydrogen adsorption on rutile SnO2 (110) surface is reported. It is found that on doping with trivalent indium, the surface becomes unstable due to the formation of bridging oxygen vacancies. At sufficiently low doping level, the surface stabilizes at an oxygen vacancy to indium ratio of 1:2. Our calculations predict that at a higher doping level of 9 at. %, this ratio becomes larger, and point out a way to synthesize p-type conducting SnO2 thin films. The binding energy of SnO2 (110) surface with adsorbed hydrogen atoms display a maximum at 3-6 at. % of indium doping. This is in good agreement with the experimental results obtained from the SnO2-based hydrogen sensor\u27s sensitivity measurements given by Drake et al. [J. Appl. Phys. 101, 104307 (2007)]. The theoretical modeling explains that the calcinations treatment can critically affect the sensitivity of the hydrogen sensor due to the enhancement of the binding energy between the SnO2 surface and the adsorbed hydrogen atoms

Oxygen evolution reaction on a N-doped Co0.5-terminated Co3O4 (001) surface

The project AP05131211 “First principles investigation on catalytic properties of N-doped Co3O4.” was funded by the Ministry of Education and Science of the Republic of Kazakhstan. The work was partly supported by COST (European Cooperation in science and Technology) Action 18234 (YM and EK). The work of T. Inerbaev was performed under the state assignment of Sobolev Institute of Geology and Mineralogy Siberian Branch of the Russian Academy of Sciences. YM and EK thank Sun-to-Chem project of ERA Net.Recent experimental findings suggest that the catalytic activity of Co3O4 for oxygen evolution reaction (OER) could be improved by nitrogen doping. We present preliminary OER modelling on a N-doped Co3O4 surface, with varying concentration of the dopant and its spatial distribution around Cooct and Cotet adsorption sites. The overpotential was calculated for two adsorption sites on seven types of N-doped Co3O4 surface. The largest calculated overpotential value for a N-doped surface was ~1V. This work is licensed under a CC BY 4.0 license.Ministry of Education and Science of the Republic of Kazakhstan, project AP0513121; COST Action 18234; Sobolev Institute of Geology and Mineralogy Siberian Branch of the Russian Academy of Sciences; Sun-to-Chem project of ERA Net; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²

Theoretical Modelling of Thermoelectric Properties of Fe2Ti1-xVxSn Heusler Alloys

Fe2TiSn is a full-Heusler alloy with 24 valence electrons per formula unit. Its electronic properties, thermal and chemical stability, relatively low cost of constituent elements make it a potential thermoelectric material for practical applications for conversion of waste heat to electricity

Color Centers in BaFBr Crystals: Experimental Study and Theoretical Modeling

This research was funded by the Ministry of Education and Science of the Republic of Kazakhstan, grant number AP14870572 \u201CExperimental-theoretical analysis of processes induced by radiation defects in scintillation materials for nuclear and space applications\u201D. In addition, the research of A.I.P. was partly supported by COST Action CA20129 \u201CMultiscale irradiation and chemistry driven processes and related technologies\u201D (MultiChem). Furthermore, the research of A.I.P and MK was partly supported by Latvian State Research Programme on Nr. VPP-IZM-CERN-2022/1-0001 and Latvian Research Project lzp-2023/1-0453. ISSP UL as the Center of Excellence, is supported through the Framework Program for European Universities, Union Horizon 2020, H2020-WIDESPREAD-01\u20132016\u20132017-TeamingPhase2, under Grant Agreement No. 739508, CAMART2 project.This study presents theoretical and experimental investigations into the electron and hole color centers in BaFBr crystals, characterizing their electronic and optical properties. Stoichiometric BaFBr crystals grown by the Steber method were used in the experiments. Radiation defects in BaFBr crystals were created by irradiation with 147 MeV 84Kr ions with up to fluences of 1010–1014 ions/cm2. The formation of electron color centers (F(F−), F2(F−), F2(Br−)) and hole aggregates was experimentally established by optical absorption spectroscopy. Performed measurements are compared with theoretical calculations. It allows us to determine the electron transition mechanisms and investigate the processes involved in photoluminescence emission in Eu-doped BaFBr materials to enhance the understanding of the fundamental electronic structure and properties of electron and hole color centers formed in BaFBr crystals. © 2024 by the authors. --//-- This is an open-access article Inerbaev, T.; Akilbekov, A.; Kenbayev, D.; Dauletbekova, A.; Shalaev, A.; Polisadova, E.; Konuhova, M.; Piskunov, S.; Popov, A.I. Color Centers in BaFBr Crystals: Experimental Study and Theoretical Modeling. Materials 2024, 17, 3340. https://doi.org/10.3390/ma17133340 published under the CC BY 4.0 licence.Latvian State Research Programme lzp-2023/1-0453, VPP-IZM-CERN-2022/1-0001; European Union Horizon 2020, H2020-WIDESPREAD-01\u20132016\u20132017-TeamingPhase2, under Grant Agreement No. 739508, CAMART2 project; European Cooperation in Science and Technology CA20129; Ministry of Education and Science of the Republic of Kazakhstan AP14870572

Quantum chemistry of quantum dots: Effects of ligands and oxidation

We report Gaussian basis set density functional theory (DFT) calculations of the structure and spectra of several colloidal quantum dots (QDs) with a (CdSe)(n) core (n=6,15,17), that are either passivated by trimethylphosphine oxide ligands, or unpassivated and oxidized. From the ground state geometry optimization results we conclude that trimethylphosphine oxide ligands preserve the wurtzite structure of the QDs. Evaporation of the ligands may lead to surface reconstruction. We found that the number of two-coordinated atoms on the nanoparticle\u27s surface is the critical parameter defining the optical absorption properties. For (CdSe)(15) wurtzite-derived QD this number is maximal among all considered QDs and the optical absorption spectrum is strongly redshifted compared to QDs with threefold coordinated surface atoms. According to the time-dependent DFT results, surface reconstruction is accompanied by a significant decrease in the linear absorption. Oxidation of QDs destroys the perfection of the QD surface, increases the number of two-coordinated atoms and results in the appearance of an infrared absorption peak close to 700 nm. The vacant orbitals responsible for this near infrared transition have strong Se-O antibonding character. Conclusions of this study may be used in optimization of engineered nanoparticles for photodetectors and photovoltaic devices

Spin Unrestricted Excited State Relaxation Dynamics in Semiconducting Systems

Atomistic modeling of light driven electron dynamics is important in studies of photoactive materials. Spin-resolved electronic structure calculations become necessary when dealing with transition metal, magnetic, and even some carbon materials, intermediates, and radicals. An approximate treatment can be pursued in the basis of spin-collinear density functional theory. Most transition-metal compounds exhibit open shell nonsinglet configurations, necessitating special treatment of electrons with α/β spin projections