--- _id: '10827' abstract: - lang: eng text: Titanium dioxide has been extensively studied in the rutile or anatase phase, while its high-pressure phases are less well-understood, despite that many are thought to have interesting optical, mechanical, and electrochemical properties. First-principles methods, such as density functional theory (DFT), are often used to compute the enthalpies of TiO2 phases at 0 K, but they are expensive and, thus, impractical for long time scale and large system-size simulations at finite temperatures. On the other hand, cheap empirical potentials fail to capture the relative stabilities of various polymorphs. To model the thermodynamic behaviors of ambient and high-pressure phases of TiO2, we design an empirical model as a baseline and then train a machine learning potential based on the difference between the DFT data and the empirical model. This so-called Δ-learning potential contains long-range electrostatic interactions and predicts the 0 K enthalpies of stable TiO2 phases that are in good agreement with DFT. We construct a pressure–temperature phase diagram of TiO2 in the range 0 < P < 70 GPa and 100 < T < 1500 K. We then simulate dynamic phase transition processes by compressing anatase at different temperatures. At 300 K, we predominantly observe an anatase-to-baddeleyite transformation at about 20 GPa via a martensitic two-step mechanism with a highly ordered and collective atomic motion. At 2000 K, anatase can transform into cotunnite around 45–55 GPa in a thermally activated and probabilistic manner, accompanied by diffusive movement of oxygen atoms. The pressures computed for these transitions show good agreement with experiments. Our results shed light on how to synthesize and stabilize high-pressure TiO2 phases, and our method is generally applicable to other functional materials with multiple polymorphs. acknowledgement: J.G.L. and B.C. acknowledge the resources provided by the Cambridge Tier-2 system operated by the University of Cambridge Research Computing Service funded by the EPSRC Tier-2 capital (Grant No. EP/P020259/1). article_number: '074106' article_processing_charge: No article_type: original author: - first_name: Jacob G. full_name: Lee, Jacob G. last_name: Lee - first_name: Chris J. full_name: Pickard, Chris J. last_name: Pickard - first_name: Bingqing full_name: Cheng, Bingqing id: cbe3cda4-d82c-11eb-8dc7-8ff94289fcc9 last_name: Cheng orcid: 0000-0002-3584-9632 citation: ama: Lee JG, Pickard CJ, Cheng B. High-pressure phase behaviors of titanium dioxide revealed by a Δ-learning potential. The Journal of chemical physics. 2022;156(7). doi:10.1063/5.0079844 apa: Lee, J. G., Pickard, C. J., & Cheng, B. (2022). High-pressure phase behaviors of titanium dioxide revealed by a Δ-learning potential. The Journal of Chemical Physics. AIP Publishing. https://doi.org/10.1063/5.0079844 chicago: Lee, Jacob G., Chris J. Pickard, and Bingqing Cheng. “High-Pressure Phase Behaviors of Titanium Dioxide Revealed by a Δ-Learning Potential.” The Journal of Chemical Physics. AIP Publishing, 2022. https://doi.org/10.1063/5.0079844. ieee: J. G. Lee, C. J. Pickard, and B. Cheng, “High-pressure phase behaviors of titanium dioxide revealed by a Δ-learning potential,” The Journal of chemical physics, vol. 156, no. 7. AIP Publishing, 2022. ista: Lee JG, Pickard CJ, Cheng B. 2022. High-pressure phase behaviors of titanium dioxide revealed by a Δ-learning potential. The Journal of chemical physics. 156(7), 074106. mla: Lee, Jacob G., et al. “High-Pressure Phase Behaviors of Titanium Dioxide Revealed by a Δ-Learning Potential.” The Journal of Chemical Physics, vol. 156, no. 7, 074106, AIP Publishing, 2022, doi:10.1063/5.0079844. short: J.G. Lee, C.J. Pickard, B. Cheng, The Journal of Chemical Physics 156 (2022). date_created: 2022-03-06T23:01:53Z date_published: 2022-02-16T00:00:00Z date_updated: 2023-08-02T14:45:46Z day: '16' department: - _id: BiCh doi: 10.1063/5.0079844 external_id: arxiv: - '2111.12968' isi: - '000796704500014' intvolume: ' 156' isi: 1 issue: '7' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/2111.12968 month: '02' oa: 1 oa_version: Preprint publication: The Journal of chemical physics publication_identifier: eissn: - '10897690' publication_status: published publisher: AIP Publishing quality_controlled: '1' scopus_import: '1' status: public title: High-pressure phase behaviors of titanium dioxide revealed by a Δ-learning potential type: journal_article user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 156 year: '2022' ...