Title: First-Principles Modeling of Yttrium Oxide and Oxyhydride: Defects, Electronic Properties, and Applications in Smart Materials
Research proposal No: 1.1.1.9/LZP/1/24/012
Duration: 01.03.2025.-29.02.2028.
Project Leader: Dr.phys. Aleksejs Gopejenko
Total budget: 184 140 EUR
European Regional Development Fund (ERDF) funding: 156 519 EUR
ISSP UL budget: 9 207 EUR
Project description:
The aim of the project is to develop reliable first-principles computational models for rare earth oxides and oxyhydrides, focusing on YO and YHO. These materials have promising applications in energy-efficient technologies like smart windows. The study explores how structural composition and defects affect their properties, supporting the development of innovative functional materials.
PROJECT PROGRESS
Time period: 29.08.2025. - 31.01.2026.
During the current reporting period, substantial progress has been achieved in the development and application of first-principles computational models for yttrium monoxide (YO) and yttrium oxyhydride (YOH). The work focused on establishing reliable computational protocols, analyzing composition-dependent electronic properties, and validating theoretical approaches using different exchange-correlation functionals.
Main Scientific Results
Reliable first-principles models for YO and YOH have been successfully developed using Density Functional Theory implemented in the CRYSTAL code. Optimized computational parameters enable accurate predictions of bulk structural and electronic properties.
Initial modeling of hcp yttrium (Y) using CRYSTAL showed that reliable lattice constants cannot be obtained within the adopted computational framework. To ensure efficient project progress, the research focus was shifted to YO and YOH systems, and WP3 and WP4 were initiated ahead of schedule. The modeling of hcp yttrium will be continued in the following months using the VASP code, which is better suited for accurate description of metallic systems.
For YO in the NaCl-type structure, the calculated lattice constant (4.78 Å) shows excellent agreement with experimental data. Density of states (DOS) analysis indicates metallic or near-metallic behavior. Systematic investigation of hydrogen incorporation into YO demonstrates strong dependence of the electronic structure on hydrogen concentration and atomic positions, leading to a gradual transition toward YOH-like electronic properties.
Modeling of oxygen incorporation into YH₂ reveals continuous electronic structure evolution during the YH₂ → YOH transformation. Fully developed YOH models exhibit semiconducting behavior. Comparative calculations using B3LYP and HSE06 hybrid exchange-correlation functionals confirm the robustness of the observed trends.
Current Status and Next Steps
The project has progressed beyond initial model development toward detailed investigation of composition-driven electronic properties. Planned activities include explicit defect modeling in YO, YH₂, and YOH, continuation of hcp yttrium modeling using VASP, and dissemination of results through publications and conferences.
Conclusions
The current reporting period resulted in validated first-principles models for yttrium oxides and oxyhydrides and new insights into the role of hydrogen and oxygen in tuning electronic properties. These results form a solid foundation for subsequent defect studies and experimental validation, supporting the long-term goal of designing functional rare-earth-based smart materials.
Time period: 01.03.2025. – 28.08.2025.
Work Package 1 (WP1) was dedicated to the adjustment of computational parameters and the development of a theoretical model for the reliable prediction of the bulk and electronic properties of Y, YO, and YHO (Month 1–Month 6). The objectives of WP1 have been fully accomplished.
A comprehensive verification of computational parameters was performed to ensure accuracy and reproducibility of the results. The influence of the Monkhorst-Pack mesh on Brillouin zone sampling, as well as the convergence behavior of bulk and supercell calculations, was systematically analyzed. Particular attention was given to the convergence of defect supercells in order to minimize artificial interactions between periodic images. Several exchange–correlation functionals were tested, and the final computational protocol was established on the basis of consistency and agreement with reference data. The reliability of the chosen model was further confirmed by validation against available experimental measurements and theoretical studies.
Main Results
The equilibrium lattice constant of YO was calculated as 4.78 Å, in very good agreement with the reported value of 4.87 Å.
Analysis of the electronic density of states (DOS) demonstrated that YO exhibits metallic-like behavior, with oxygen atoms dominating the valence band and yttrium atoms dominating the conduction band.
Hydrogen incorporation into YO (YOH) resulted in a lattice expansion to 5.61 Å, accompanied by local lattice distortions depending on the positioning of hydrogen atoms in tetrahedral interstitial sites.
YOH was identified as a semiconductor with a calculated band gap of 3.13 eV. The valence band is primarily composed of contributions from oxygen and hydrogen, while the conduction band is dominated by yttrium.
These findings establish that hydrogen incorporation has a pronounced effect on both the structural and electronic properties of YO, inducing a transition from metallic-like to semiconducting behavior.
Ongoing Work
The implementation of WP2 is in progress, ensuring the continuity of the research program. Calculations of the Y lattice containing O and H defects have been initiated. These studies will provide further insight into defect-driven modifications of the structural and electronic properties of yttrium-based materials.
Conclusion
The activities of WP1 have been completed in full. The computational framework has been optimized, a validated theoretical model has been established, and the bulk and electronic properties of Y, YO, and YHO have been systematically characterized. The results obtained provide a robust foundation for subsequent investigations of defect structures and functional properties in rare-earth oxide materials.