Ab initio modelling of the effects of varying Zr (Ti) concentrations on the atomic and electronic properties of stoichiometric PZT solid solutions

Abstract Lead zirconate titanate Pb(ZrxTi1−x)O3 solid solution is considered as one of the most advanced ferroelectric and piezoelectric materials. Consequent variation of Zr (Ti) concentrations significantly affects the atomic and electronic properties of PZT structures. To perform ab initio modelling of different morphologies for lead zirconate titanate, we are using approach of hybrid density functional B3PW as implemented in CRYSTAL14 computer code. In this study, we are performing large-scale calculations of such PZT parameters as optimized lattice constants, atomic charges and bond populations, as well as band structure (e.g., band gap) and density of states.

First Principles Calculations of Atomic and Electronic Structure of TiAl3+- and TiAl2+-Doped YAlO3

In this paper, the density functional theory accompanied with linear combination of atomic orbitals (LCAO) method is applied to study the atomic and electronic structure of the Ti3+ and Ti2+ ions substituted for the host Al atom in orthorhombic Pbnm bulk YAlO3 crystals. The disordered crystalline structure of YAlO3 was modelled in a large supercell containing 160 atoms, allowing simulation of a substitutional dopant with a concentration of about 3%. In the case of the Ti2+-doped YAlO3, compensated F-center (oxygen vacancy with two trapped electrons) is inserted close to the Ti to make the unit cell neutral. Changes of the interatomic distances and angles between the chemical bonds in the de…

First Principles Calculations of Atomic and Electronic Structure of Ti3+Al- and Ti2+Al-Doped YAlO3

M.G.B. appreciates support from the Chongqing Recruitment Program for 100 Overseas Innovative Talents (grant no. 2015013), the Program for the Foreign Experts (grant no. W2017011), Wenfeng High-end Talents Project (grant no. W2016-01) offered by the Chongqing University of Posts and Telecommunications (CQUPT), Estonian Research Council grant PUT PRG111, European Regional Development Fund (TK141), and NCN project 2018/31/B/ST4/00924. This study was supported by a grant from Latvian Research Council No. LZP-2018/1-0214 (for AIP). Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Program H202…

The electronic properties of an oxygen vacancy at ZrO2-terminated (001) surfaces of a cubic PbZrO3: computer simulations from the first principles

Combining B3PW hybrid exchange-correlation functional within the density functional theory (DFT) and a supercell model, we calculated from the first principles the electronic structure of both ideal PbZrO(3) (001) surface (with ZrO(2)- and PbO-terminations) and a neutral oxygen vacancy also called the F center. The atomic relaxation and electronic density redistributions are discussed. Thermodynamic analysis of pure surfaces indicates that ZrO(2) termination is energetically more favorable than PbO-termination. The O vacancy on the ZrO(2)-surface attracts approximately 0.3 e (0.7 e in the bulk PbZrO(3)), while the remaining electron density from the missing O(2-) ion is localized mostly on …

Ab initio modelling of Y-O cluster formation in γ-Fe lattice

Ab initio modelling of Y and O impurity atoms as well as VFe vacancies in the fcc-Fe lattice is performed in order to calculate the interactions between these defects, which are important for understanding of nanoparticles’ formation within the oxide dispersed strengthened steels. Large scale parallel calculations based on plane-wave method realised in VASP computer code show that VFe vacancies considerably influence the binding between the impurity atoms. In this study, we present the results of performed calculations providing the detailed information about the binding energies between the defects, the changes of their effective charges as well as displacements of the substitute atoms rel…

Modeling of yttrium, oxygen atoms and vacancies in γ-iron lattice

Abstract Development of the oxide dispersion strengthened (ODS) steels for fission and fusion reactors requires a deep understanding of the mechanism and kinetics of Y 2 O 3 nanoparticle precipitation in the steel matrix. Therefore, it is necessary to perform a large-scale theoretical modeling of the Y 2 O 3 formation. In the current study, a series of first-principles calculations have been performed on different elementary clusters consisting of pair and triple solute atoms and containing: (i) the Y–Fe-vacancy pairs, (ii) the two Y atoms substituted for Fe lattice atoms and (iii) the O impurity atoms dissolved in the steel matrix. The latter is represented by a face-centered cubic γ-Fe si…

Time-Dependent Density Functional Theory Calculations of N- and S-Doped TiO2 Nanotube for Water-Splitting Applications

This research was funded by the Latvian Council of Science grant LZP-2018/2-0083. Institute of Solid State Physics, University of Latvia, as the Center of Excellence, has received funding from the European Union?s Horizon 2020 Framework Program H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under Grant Agreement No. 739508, project CAMART2.

Interaction Between Oxygen and Yttrium Impurity Atoms as well as Vacancies in fcc Iron Lattice: Ab Initio Modeling

Synthesis of advanced radiation-resistant steels as construction materials for nuclear reactors, which contain the uniformly distributed yttria precipitates (ODS steels), is an important task for ecological security of nuclear plants. The initial stage of theoretical simulation on oxide cluster growth in the steel matrix is a large-scale ab initio modeling on pair- and triple-wise interaction between the Y and O impurity atoms as well as Fe vacancies, including their different combinations, in the paramagnetic face-centered-cubic (fcc) iron lattice. Calculations on the pair of Y atoms have shown that no bonding appears between them, whereas a certain attraction has been found between Y subs…

Visualization of the Renewable Energy Resources

The methods of the renewable energy resources visualization are analysed in this work, the examples of the systems and possible architecture of the renewable energy monitoring systems of the Republic of Kazakhstan are considered. Successful practices are analysed, the leading scientific organization in the field of green energy are considered, a comparative analysis of geographic information systems and data sources in the field of green energy is performed. Possible software architecture of the system based on 3M paradigm of geographic information system (multilayer views, multilayer architecture and multi-agent interaction) is considered.

Using Applications and Tools to Visualize ab initio Calculations Performed in VASP

Visualization of the results of the ab initio calculations is important for the analysis of these results. It improves the quality of the analysis by supplementing the plain numbers received as the output of the calculations with various graphical images and facilitates the analysis of the results. In addition to that visualization helps avoiding some mistakes or inconsistencies. Various tools have been used in this work to construct the unit cell models of the calculated lattices, to check and analyze the calculated lattice structure before and after the relaxation, to plot total and difference electron charge density maps.

Energy Consumption Management of the Automated Self-service Centre’s Storage Module: Models and Simulations

Ab initio modelling of the initial stages of the ODS particle formation process

Abstract Oxide-Dispersion Strengthened (ODS) steels with Y2O3 nanoparticles are promising structural materials for fision and future fusion reactors. A large number of experimental as well as theoretical studies provided valuable information on the ODS particle formation process. However, some important details of this process still remain unexplained. We present the results of ab initio VASP calculations of the initial steps of the ODS particle formation. At these steps Y solute atoms are stabilized in the Fe lattice by vacancies, which create a basis for the future growth of Y2O3-particle. Interaction of multiple vacancies and solution Y and O atoms has been studied in various combination…

A Method of Three-Dimensional Visualization of Molecular Processes of Apoptosis

Apoptosis or programmed cell death plays an important role in many physiological states and diseases. Detection of apoptotic cells, tracing the development of apoptosis, drug development and regulation of apoptosis are an important parts of basic research in medicine. A large number of models have been developed that are based on the differential equations of the chemical kinetics, and can be expressed in a uniform notation using some XML-based languages, such as SBML and CellML. We describe the CellML and the simulation environment OpenCell herein. These tools can display models schematically and output results in the form of graphs showing time dependencies of component concentrations. Ho…

Ideāla un defektīva svina cirkonāta atomāra un elektroniskā struktūra: aprēķini no pirmajiem principiem

Aprēķini no pirmajiem principiem ir viena no plašāk izmantojamām metodēm atšķirīgu materiālu teorētiskiem pētījumiem. Šajā darbā CRYSTAL programma tika izmantota, lai izpildītu aprēķinus no pirmajiem principiem. Šī programma izmanto kvantu ķīmijas metodes, kuras ir bāzētas uz Hartrī-Foka un blīvuma funkcionāļa teorijas metodēm. Šajā darbā ideāla un defekta saturoša (F-centru) svina cirkonāta (PZO) atomāras un elektroniskās struktūras apjomā un (001) virsmā tika aprēķinātas. Iegūti rezultāti ir salīdzināti ar stroncija titanāta (STO) un svina titanāta (PTO) aprēķiniem. Teorētisko aprēķinu rezultāti, kuri ir iegūti ar CRYSTAL programmas palīdzību, ir kvalitatīvā saskaņā ar zināmajiem eksperim…

Ab initio modelling of the Y, O, and Ti solute interaction in fcc-Fe matrix

Abstract Strengthening of the ODS steels by Y2O3 precipitates permits to increase their operation temperature and radiation resistance, which is important in construction materials for future fusion and advanced fission reactors. Both size and spatial distribution of oxide particles significantly affect mechanical properties and radiation resistance of ODS steels. Addition of the Ti species (present also as a natural impurity atoms in iron lattice) in the particles of Y2O3 powder before their mechanical alloying leads to the formation of YTiO3, Y2TiO5, and Y2Ti2O7 nanoparticles in ODS steels. Modelling of these nanoparticle formation needs detailed knowledge of the energetic interactions be…

Ab initio simulation of yttrium oxide nanocluster formation on fcc Fe lattice

Using results of density functional theory (DFT) calculations the first attempt towards the understanding of Y2O3 particles formation in oxide dispersed strengthened (ODS) ferritic–martensitic steels was performed. The present work includes modeling of single defects (O impurity atom, Fe vacancy and Y substitute atom), interaction between substituted Y atoms, Y–Fe vacancy pairs and oxygen impurity atoms in the iron matrix. The calculations have showed the repulsive interaction between the two Y substitute atoms at any separation distances that might mean that the oxygen atoms or O atoms with vacancies are required to form binding between atoms in the yttrium oxide nanoclusters.

Ab Initio Modeling of Y and O Solute Atom Interaction in Small Clusters within the bcc Iron Lattice

This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euroatom research and training programme 2014–2018 under grant agreement No 633053. The authors are indebted to A. Möslang and P. V. Vladimirov for stimulating discussions. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

Itritija un skābekļa nogulsnējumu fcc-Fe kristālrežģī modelēšana no pirmajiem principiem

Elektroniskā versija nesatur pielikumus

Ab initio modelling of titanium impurities in α-Fe lattice

Abstract Reduced activation ferritic-martensitic (RAFM) as well as ferritic steels strengthened by yttrium oxide are considered as candidate materials for future fusion and advanced fission reactors. Addition of Ti during the manufacturing of the oxide dispersed strengthened (ODS) leads to the formation of yttrium titanium oxide particles, which size is smaller compared to yttrium oxide particles. This improves the mechanical properties and radiation resistance of the ODS steels. DFT calculations of Ti impurities have been performed to determine the factors contributing to the formation of the nanoparticles in α-Fe (bcc-Fe) based steels. The interaction energies between TiFe-OFe, TiFe-Ooct,…