{"title":"First-principles calculations of proton defect properties in Ca-doped YPO4","authors":"Gyeongseo Lee, Takafumi Ogawa, Kazuki Shitara, Akihide Kuwabara","doi":"10.1039/d4cp02887b","DOIUrl":null,"url":null,"abstract":"YPO<small><sub>4</sub></small> has a xenotime-type structure with one-dimensional percolating channels along the c-axis, and Ca-doped YPO<small><sub>4</sub></small> exhibits proton conduction. In the present study, using first-principles calculations, we investigate the behaviors of proton solutions in 3 mol% Ca-doped YPO<small><sub>4</sub></small> in the intermediate temperature range on the basis of point-defect formation energies, defect concentrations, and migration barriers. Although the charge-neutrality condition is mainly satisfied by Ca<small><sup>′</sup></small><small><sub>Y</sub></small> and OH<small><sup>•</sup></small><small><sub>O</sub></small> defects within the defect formation energy diagrams, the Ca<small><sup>′</sup></small><small><sub>Y</sub></small> + OH<small><sup>•</sup></small><small><sub>O</sub></small> defect complex has the lowest formation energy and the highest concentration among examined defects under various temperature and partial-pressure conditions. The migration barriers of isolated protons in the [100] and [001] directions, as obtained from nudged elastic band (NEB) calculations, are 0.49 and 0.17 eV, respectively, confirming that protons in the YPO<small><sub>4</sub></small> crystal exhibit anisotropic diffusion and are likely to migrate along the c-axis channels. The activation energy estimated by the sum of the migration energy and the association energy for the Ca<small><sup>′</sup></small><small><sub>Y</sub></small> + OH<small><sup>•</sup></small><small><sub>O</sub></small> defect complex is comparable to the reported experimental value. Based on concentration calculations and diffusion-property analyses, we identified the Ca doping conditions and temperature ranges that govern proton conduction in YPO<small><sub>4</sub></small> and elucidated the diffusion pathways.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":2.9000,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Physical Chemistry Chemical Physics","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1039/d4cp02887b","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
引用次数: 0
Abstract
YPO4 has a xenotime-type structure with one-dimensional percolating channels along the c-axis, and Ca-doped YPO4 exhibits proton conduction. In the present study, using first-principles calculations, we investigate the behaviors of proton solutions in 3 mol% Ca-doped YPO4 in the intermediate temperature range on the basis of point-defect formation energies, defect concentrations, and migration barriers. Although the charge-neutrality condition is mainly satisfied by Ca′Y and OH•O defects within the defect formation energy diagrams, the Ca′Y + OH•O defect complex has the lowest formation energy and the highest concentration among examined defects under various temperature and partial-pressure conditions. The migration barriers of isolated protons in the [100] and [001] directions, as obtained from nudged elastic band (NEB) calculations, are 0.49 and 0.17 eV, respectively, confirming that protons in the YPO4 crystal exhibit anisotropic diffusion and are likely to migrate along the c-axis channels. The activation energy estimated by the sum of the migration energy and the association energy for the Ca′Y + OH•O defect complex is comparable to the reported experimental value. Based on concentration calculations and diffusion-property analyses, we identified the Ca doping conditions and temperature ranges that govern proton conduction in YPO4 and elucidated the diffusion pathways.
期刊介绍:
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