Ab initio Calculations for SrTiO_3 (100) Surface Structure

Results of detailed calculations for SrTiO_3 (100) surface relaxation and the electronic structure for the two different terminations (SrO and TiO_2) are discussed. These are based on ab initio Hartree-Fock (HF) method with electron correlation corrections and Density Functional Theory (DFT) with different exchange-correlation functionals, including hybrid (B3PW, B3LYP) exchange techniques. Results are compared with previous ab initio plane wave LDA calculations. All methods agree well on both surface energies and on atomic displacements. Considerable increase of Ti[Single Bond]O chemical bond covalency nearby the surface is predicted, along with a gap reduction, especially for the TiO_2 termination

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