Review of Systematic Tendencies in (001), (011) and (111) Surfaces Using B3PW as Well as B3LYP Computations of BaTiO3, CaTiO3, PbTiO3, SrTiO3, BaZrO3, CaZrO3, PbZrO3 and SrZrO3 Perovskites

This study was funded by the Latvian Council of Science Grant Number: LZP-2021/1-464. The Institute of Solid State Physics, University of Latvia (Latvia), as the Centre of Excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase2 under Grant Agreement No. 739508, project CAMART-2.We performed B3PW and B3LYP computations for BaTiO3 (BTO), CaTiO3 (CTO), PbTiO3 (PTO), SrTiO3 (STO), BaZrO3 (BZO), CaZrO3 (CZO), PbZrO3 (PZO) and SrZrO3 (SZO) perovskite neutral (001) along with polar (011) as well as (111) surfaces. For the neutral AO- as well as BO2-terminated (001) surfaces, in most cases, all upper-layer atoms relax inwards, although the second-layer atoms shift outwards. On the (001) BO2-terminated surface, the second-layer metal atoms, as a rule, exhibit larger atomic relaxations than the second-layer O atoms. For most ABO3 perovskites, the (001) surface rumpling s is bigger for the AO- than BO2-terminated surfaces. In contrast, the surface energies, for both (001) terminations, are practically identical. Conversely, different (011) surface terminations exhibit quite different surface energies for the O-terminated, A-terminated and BO-terminated surfaces. Our computed ABO3 perovskite (111) surface energies are always significantly larger than the neutral (001) as well as polar (011) surface energies. Our computed ABO3 perovskite bulk B-O chemical bond covalency increases near their neutral (001) and especially polar (011) surfaces.--//-- This is an open access article Eglitis, R.I.; Jia, R. Review of Systematic Tendencies in (001), (011) and (111) Surfaces Using B3PW as Well as B3LYP Computations of BaTiO3, CaTiO3, PbTiO3, SrTiO3, BaZrO3, CaZrO3, PbZrO3 and SrZrO3 Perovskites. Materials 2023, 16, 7623. https://doi.org/10.3390/ma16247623 published under the CC BY 4.0 licence.This study was funded by the Latvian Council of Science Grant Number: LZP-2021/1-464. The Institute of Solid State Physics, University of Latvia (Latvia), as the Centre of Excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase2 under Grant Agreement No. 739508, project CAMART-2

Tendencies in abo3 perovskite and srf2, baf2 and caf2 bulk and surface f‐center ab initio computations at high symmetry cubic structure

This research was partly funded by the Latvian Council of Science project No. LZP‐ 2020/2‐0009 (for R. Eglitis), as well as the ERAF Project No. 1.1.1.1/18/A/073. We express our gratitude for the financial support from Latvian–Ukraine cooperation Project No. Latvia–Ukraine LV‐ UA/2021/5. The Institute of Solid State Physics, University of Latvia (Latvia), as the Centre of Excellence has received funding from the European Unions Horizon 2020 Framework Pro‐ gramme H2020‐WIDESPREAD01‐2016‐2017‐Teaming Phase2 under Grant Agreement No. 739508, project CAMART2.We computed the atomic shift sizes of the closest adjacent atoms adjoining the (001) surface F‐center at ABO3 perovskites. They are significantly larger than the atomic shift sizes of the closest adjacent atoms adjoining the bulk F‐center. In the ABO3 perovskite matrixes, the electron charge is significantly stronger confined in the interior of the bulk oxygen vacancy than in the interior of the (001) surface oxygen vacancy. The formation energy of the oxygen vacancy on the (001) surface is smaller than in the bulk. This microscopic energy distinction stimulates the oxygen vacancy segregation from the perovskite bulk to their (001) surfaces. The (001) surface F‐center created defect level is nearer to the (001) surface conduction band (CB) bottom as the bulk F‐center created defect level. On the contrary, the SrF2, BaF2 and CaF2 bulk and surface F‐center charge is almost perfectly confined to the interior of the fluorine vacancy. The shift sizes of atoms adjoining the bulk and surface F‐centers in SrF2, CaF2 and BaF2 matrixes are microscopic as compared to the case of ABO3 perovskites. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. Published under the CC BY 4.0 license.Latvian Council of Science project No. LZP‐ 2020/2‐0009; ERAF Project No. 1.1.1.1/18/A/073; Latvian–Ukraine cooperation Project No. Latvia–Ukraine LV‐ UA/2021/5. The Institute of Solid State Physics, University of Latvia (Latvia), as the Centre of Excellence has received funding from the European Unions Horizon 2020 Framework Pro‐ gramme H2020‐WIDESPREAD01‐2016‐2017‐Teaming Phase2 under Grant Agreement No. 739508, project CAMART2

Review of First Principles Simulations of STO/BTO, STO/PTO, and SZO/PZO (001) Heterostructures

We acknowledge the financial support from our funder the Latvian Council of Science. The funding number is Grant No. LZP-2020/1-0345. The Institute of Solid-State Physics, University of Latvia (Latvia), as a center of excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase 2 under Grant Agreement No. 739508, project CAMART2.In this study, we review our first-principles simulations for STO/BTO, STO/PTO, and SZO/PZO (001) heterostructures. Specifically, we report ab initio B3PW calculations for STO/BTO, STO/PTO, and SZO/PZO (001) interfaces, considering non-stoichiometric heterostructures in the process. Our ab initio B3PW calculations demonstrate that charge redistribution in the (001) interface region only subtly affects electronic structures. However, changes in stoichiometry result in significant shifts in band edges. The computed band gaps for the STO/BTO, STO/PTO, and SZO/PZO (001) interfaces are primarily determined according to whether the topmost layer of the augmented (001) film has an AO or BO2 termination. We predict an increase in the covalency of B-O bonds near the STO/BTO, STO/PTO, and SZO/PZO (001) heterostructures as compared to the BTO, PTO, and PZO bulk materials. --//-- This is an open access article R.I. Eglitis*, D. Bocharov, S. Piskunov, R. Jia; Review of first principles simulations of STO/BTO, STO/PTO, and SZO/PZO (001) heterostructures; Crystals, 2023, 13, 799 (pp. 1-25); DOI: 10.3390/cryst13050799; https://www.mdpi.com/2073-4352/13/5/799 published under the CC BY 4.0 licence.Latvian Council of Science Grant No. LZP-2020/1-0345. The Institute of Solid-State Physics, University of Latvia (Latvia), as a center of excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase 2 under Grant Agreement No. 739508, project CAMART2

Systematic trends in YAlO3, SrTiO3, BaTiO3, BaZrO3 (001) and (111) surface ab initio calculations

We greatly acknowledge the financial support via Latvian-Ukrainian Joint Research Project No. LV-UA/2018/2, Latvian Council of Science Grant No. 2018/2-0083 “Theoretical prediction of hybrid nanostructured photocatalytic materials for efficient water splitting”, Latvian Council of Science Grant No. 2018/1-0214 as well as ERAF Project No. 1.1.1.1/18/A/073.The paper presents and discusses the results of performed calculations for YAlO3 (111) surfaces using a hybrid B3LYP description of exchange and correlation. Calculation results for SrTiO3, BaTiO3 and BaZrO3 (111) as well as YAlO3, SrTiO3, BaTiO3 and BaZrO3 (001) surfaces are listed for comparison purposes in order to point out systematic trends common for these four ABO3 perovskite (001) and (111) surfaces. According to performed ab initio calculations, the displacement of (001) and (111) surface metal atoms of YAlO3, SrTiO3, BaTiO3 and BaZrO3 perovskite, upper three surface layers for both AO and BO2 (001) as well as AO3 and B (111) surface terminations, in most cases, are considerably larger than that of oxygen atoms. The YAlO3, SrTiO3, BaTiO3 and BaZrO3 (001) surface energies for both calculated terminations, in most cases, are almost equal. In contrast, the (111) surface energies for both AO3 and B-terminations are quite different. Calculated (111) surface energies always are much larger than the (001) surface energies. As follows from performed ab initio calculations for YAlO3, SrTiO3, BaTiO3 and BaZrO3 perovskites, the AO- and BO2-terminated (001) as well as AO3- and B-terminated (111) surface bandgaps are almost always reduced with respect to their bulk bandgap values. ---- / / / ---- This is the preprint version of the following article: Roberts Eglitis, J. Purans, A. I. Popov and Ran Jia,Systematic trends in YAlO3, SrTiO3, BaTiO3, BaZrO3 (001) and (111) surface ab initio calculations, JInternational Journal of Modern Physics B, Vol. 33, No. 32 (2019) 1950390, DOI https://doi.org/10.1142/S0217979219503909, which has been published in final form at https://www.worldscientific.com/doi/abs/10.1142/S0217979219503909. This article may be used for non-commercial purposes in accordance with World Scientific Publishing Terms and Conditions for Sharing and Self-Archiving. The copyright of this work belongs to the publisher.Latvian-Ukrainian Joint Research Project No. LV-UA/2018/2; Latvian Council of Science Grant No. 2018/2-0083; Latvian Council of Science Grant No. 2018/1-0214; ERAF Project No. 1.1.1.1/18/A/073; 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

Ab initio calculations of CaZrO3 (011) surfaces: systematic trends in polar (011) surface calculations of ABO3 perovskites

Financial support via Latvian-Ukrainian Joint Research Project No. LV-UA/2018/2 for A. I. Popov, Latvian Council of Science Project No. 2018/2-0083 “Theoretical prediction of hybrid nanostructured photocatalytic materials for efficient water splitting” for R. I. Eglitis and J. Kleperis as well as ERAF project No. 1.1.1.1/18/A/073 for R. I. Eglitis and J. Purans is greatly acknowledged.By means of the CRYSTAL computer program package, first-principles calculations of polar ZrO-, Ca- and O-terminated CaZrO3 (011) surfaces were performed. Our calculation results for polar CaZrO3 (011) surfaces are compared with the previous ab initio calculation results for ABO3 perovskite (011) and (001) surfaces. From the results of our hybrid B3LYP calculations, all upper-layer atoms on the ZrO-, Ca- and O-terminated CaZrO3 (011) surfaces relax inwards. The only exception from this systematic trend is outward relaxation of the oxygen atom on the ZrO-terminated CaZrO3 (011) surface. Different ZrO, Ca and O terminations of the CaZrO3 (011) surface lead to a quite different surface energies of 3.46, 1.49, and 2.08 eV. Our calculations predict a considerable increase in the Zr–O chemical bond covalency near the CaZrO3 (011) surface, both in the directions perpendicular to the surface (0.240e) as well as in the plane (0.138e), as compared to the CaZrO3 (001) surface (0.102e) and to the bulk (0.086e). Such increase in the B–O chemical bond population from the bulk towards the (001) and especially (011) surfaces is a systematic trend in all our eight calculated ABO3 perovskites. This work is licensed under a CC BY license.Latvian-Ukrainian Joint Research Project No. LV-UA/2018/2; Latvian Council of Science Project No. 2018/2-0083; ERAF project No. 1.1.1.1/18/A/073; 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

Systematic Trends in Hybrid-DFT Computations of BaTiO3/SrTiO3, PbTiO3/SrTiO3 and PbZrO3/SrZrO3 (001) Hetero Structures

We acknowledge the financial support from the funder—Latvian Council of Science. The funding number is: Grant No. LZP-2020/1-0345. The Institute of Solid State Physics, University of Latvia (Latvia), as the Centre of Excellence, has received funding from the European Unions Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase2 under Grant Agreement No. 739508, project CAMART-2.We performed predictive hybrid-DFT computations for PbTiO3, BaTiO3, SrTiO3, PbZrO3 and SrZrO3 (001) surfaces, as well as their BaTiO3/SrTiO3, PbTiO3/SrTiO3 and PbZrO3/SrZrO3 (001) heterostructures. According to our hybrid-DFT computations for BO2 and AO-terminated ABO3 solid (001) surfaces, in most cases, the upper layer ions relax inwards, whereas the second layer ions shift upwards. Our hybrid-DFT computed surface rumpling s for the BO2-terminated ABO3 perovskite (001) surfaces almost always is positive and is in a fair agreement with the available LEED and RHEED experiments. Computed B-O atom chemical bond population values in the ABO3 perovskite bulk are enhanced on its BO2-terminated (001) surfaces. Computed surface energies for BO2 and AO-terminated ABO3 perovskite (001) surfaces are comparable; thus, both (001) surface terminations may co-exist. Our computed ABO3 perovskite bulk Γ-Γ band gaps are in fair agreement with available experimental data. BO2 and AO-terminated (001) surface Γ-Γ band gaps are always reduced with regard to the respective bulk band gaps. For our computed BTO/STO and PTO/STO (001) interfaces, the average augmented upper-layer atom relaxation magnitudes increased by the number of augmented BTO or PTO (001) layers and always were stronger for TiO2-terminated than for BaO or PbO-terminated upper layers. Our B3PW concluded that BTO/STO, as well as SZO/PZO (001) interface Γ-Γ band gaps, very strongly depends on the upper augmented layer BO2 or AO-termination but considerably less so on the number of augmented (001) layers. © 2022 by the authors. --//-- This is an open access article Eglitis R.I., Piskunov S., Popov A.I., Purans J., Bocharov D., Jia R., "Systematic Trends in Hybrid-DFT Computations of BaTiO3/SrTiO3, PbTiO3/SrTiO3 and PbZrO3/SrZrO3 (001) Hetero Structures", (2022) Condensed Matter, 7 (4), art. no. 70, DOI: 10.3390/condmat7040070 published under the CC BY 4.0 licence.Latvian Council of Science Grant No. LZP-2020/1-0345; Institute of Solid-State Physics, University of Latvia has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2

Effects of Electron Correlation inside Disordered Crystals

S.P.K. acknowledges support by the National Academy of Sciences of Ukraine (Project No.0116U002067). Calculations were performed using Latvian Super Cluster (LASC), located in the Center of Excellence at Institute of Solid State Physics, the University of Latvia, which is supported by European Union Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-Teaming. Phase two under Grant Agreement No. 739508, project CAMART2.We propose a novel approach for characterising the electron spectrum of disordered crystals constructed from a Hamiltonian of electrons as well as phonons and a diagram approach for Green’s function. The system’s electronic states were modelled by means of the multi‐band, tight-binding approach. The system’s Hamiltonian is described based on the electron wave functions at the field of the atom nucleus. Our novel approach incorporates the long‐range Coulomb interplay of electrons located in different lattice positions. Explicit interpretations of Green’s functions are derived using a diagram method.Equations are obtained for the vertex components for the mass operators of the electron–electron as well aselectron–phonon interplays. A system of equations for the spectrum of elementary excitations in the crystal is obtained, in which the vertex components for the mass operators of electron–electron as well as electron–phonon interplays are renormalised. Thismakes it possible to perform numerical computationsfor the system’s energy spectrum with a predetermined accuracy. In contrast to other approaches in which electron correlations are only taken into account in the limiting cases of an infinitely large and infinitesimal electron density, in this method, electron correlations are described in the general case of an arbitrary density. We obtained the cluster expansion of the density of states (DOS) of the disordered systems. We demon-strate that the addition of the electron‐scattering mechanismsto the clusters is decreasing. This hap-pens due to a growing number of positions in the cluster, which hang ontothe small parameter. The computing exactness is fixed by a small parameter for cluster expansion of Green’s functions of electrons as well as phonons. © 2022 by the authors. Submitted for possible open access.--//-- This is an open access article Kruchinin, S.P.; Eglitis, R.I.; Babak, V.P.; Vyshyvana, I.G.; Repetsky, S.P. Effects of Electron Correlation inside Disordered Crystals. Crystals 2022, 12, 237. https://doi.org/10.3390/cryst12020237; published under the CC BY 4.0 licence.European Union Horizon 2020 Framework Programme H2020‐WIDESPREAD‐01‐2016‐2017‐Teaming; National Academy of Sciences of Ukraine 0116U002067; 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

Co-doping with boron and nitrogen impurities in T-carbon

Previously, Ren et al. [Chem. Phys. 518, 69–73, 2019] reported the failure of Boron-Nitrogen (B-N) co-doping as inter B-N bond in T-carbon. In present work, a B-N atom pair is introduced in T-carbon as p-n co-dopant to substitute two carbon atoms in the same carbon tetrahedron and form an intra B-N bond. The stability of this doping system is verified from energy, lattice dynamic, and thermodynamic aspects. According to our B3PW calculations, B-N impurities in this situation can reduce the band gap of T-carbon from 2.95 eV to 2.55 eV, making this material to be a promising photocatalyst. Through the study of its transport properties, we can also conclude that B-N co-doping cannot improve the thermoelectric performance of T-carbon.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 CAMART

Certain doping concentrations caused half-metallic graphene

This work is supported by National Natural Science Foundation of China (Grant No. 21173096).The singly B and N doped graphene systems are carefully studied. The highly concentrated dopants cause a spin polarization effect in the systems. The spin polarization limits are affirmed in the singly B and N doped graphene systems through periodic hybrid density functional theory studies. The spin polarization effects must be considered indeed in the B and N doped graphene systems if the dopant concentration is above 3.1% and 1.4%, respectively. The system symmetry cooperating with the presence of the spin polarization brings half-metallic properties into the doping systems. The semiconducting channels in the half-metallic systems are in two different spin directions due to the different electron configurations of the B and N dopants in graphene.National Natural Science Foundation of China 21173096; 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 CAMART

First principles hybrid Hartree–Fock–DFT calculations of bulk and (001) surface F centers in oxide perovskites and alkaline-earth fluorides

Valuable discussions with E. A. Kotomin are gratefully acknowledged. Research contribution of R. E. and A. I. P. has been performed within the framework of the EUROfusion Enabling Research project: ENR-MFE19.ISSP-UL-02 “Advanced experimental and theoretical analysis of defect evolution and structural disordering in optical and dielectric materials for fusion applications.” The views and opinions expressed herein do not necessarily reflect those of the European Commission.We report the results of ab initio calculations and analysis of systematic trends for the F centers in the bulk and on the (001) surface in oxide perovskites, such as BaTiO3, SrTiO3, SrZrO3, and PbZrO3, with a corresponding comparison of the F centers in perovskites with those in alkaline earth metal fluorides (CaF2, BaF2, and SrF2). It was found that in perovskites in both bulk F centers and those on their (001) surfaces, two nearest to the vacancy Ti or Zr atoms repel each other, while the next nearest O atoms relax towards the oxygen vacancy. It was also found that the obtained relaxations of atoms in the nearest neighborhood around the F center in ABO3 perovskites are generally larger than in alkaline earth metal fluorides. The bulk and (001)-terminated surface F center ground states in BaTiO3, SrTiO3, and SrZrO3 perovskites are located 0.23, 0.69, 1.12 eV, and 0.07, 0.25, 0.93 eV, respectively, below the conduction band bottom, indicating that the F center is a shallow donor. The vacancies in BaTiO3, SrZrO3, and PbZrO3 are occupied with 1.103e, 1.25e, and 0.68e, respectively, whereas slightly smaller charges, only 1.052e, 1.10e, and 0.3e are localized inside the F center on the perovskite (001) surface. In contrast to the partly covalent ABO3 perovskites, charge is well localized (around 80%) inside the ionic CaF2, BaF2, and SrF2 fluorine vacancy. ---- / / / ---- This is the preprint version of the following article: R. Eglitis, A. I. Popov, J. Purans and Ran Jia,First principles hybrid Hartree-Fock-DFT calculations of bulk and (001) surface F centers in oxide perovskites and alkaline-earth fluorides, Low Temperature Physics,46, 1206 (2020), DOI ttps://doi.org/10.1063/10.0002475, which has been published in final form at https://aip.scitation.org/doi/10.1063/10.0002475. This article may be used for non-commercial purposes in accordance with American Institute of Physics terms and conditions for sharing and self-archiving.EUROfusion Enabling Research project: ENR-MFE19.ISSP-UL-02; 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