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<p>Accurate evaluation of high-order anharmonic interactions in complex crystalline systems requires prohibitively large computational resources, limiting mechanistic insight into defect scattering and the resulting suppression of thermal conductivity in <i>β</i>-Ga<sub>2</sub>O<sub>3</sub>. In this study, machine learning-accelerated first-principles calculations were used to evaluate both harmonic and anharmonic phonon properties over a broad range. This approach incorporates both phonon-phonon and defect scattering within a unified framework. Oxygen vacancies lead to a pronounced phonon redshift, a sharp reduction in phonon group velocity, and a substantial decrease in phonon lifetime, collectively indicating strong defect-induced phonon scattering. As the vacancy concentration increases, phonon frequencies and lifetimes exhibit an approximately linear downward trend. Concurrently, the available phase space and anharmonic matrix elements associated with low-frequency phonon scattering are enhanced. These combined effects result in a rapid suppression of the lattice thermal conductivity and phonon mean free path, particularly in the low-frequency transport regime. This study not only avoids the theoretical limitations associated with calculating high-order anharmonic terms but also systematically quantifies the degradation of thermal conductivity with increasing vacancy concentration, thereby elucidating the microscopic mechanisms governing defect-induced anharmonicity and advancing the understanding of anharmonic lattice dynamics in <i>β</i>-Ga<sub>2</sub>O<sub>3</sub>.</p>

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Strong phonon scattering and suppressed thermal transport induced by oxygen vacancy in β-Ga2O3 elucidated via machine learning

  • 期刊论文

  • 发表日期：

    2026年3月19日

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  • Sihan Yan,
  • Yajing Gu,
  • Xueqiang Ji,
  • Jiahan Zhang,
  • Lincong Shu,
  • Baijie Cheng,
  • Chee-Keong Tan,
  • Shan Li,
  • Zeng Liu,
  • Weihua Tang

摘要

Accurate evaluation of high-order anharmonic interactions in complex crystalline systems requires prohibitively large computational resources, limiting mechanistic insight into defect scattering and the resulting suppression of thermal conductivity in β-Ga2O3. In this study, machine learning-accelerated first-principles calculations were used to evaluate both harmonic and anharmonic phonon properties over a broad range. This approach incorporates both phonon-phonon and defect scattering within a unified framework. Oxygen vacancies lead to a pronounced phonon redshift, a sharp reduction in phonon group velocity, and a substantial decrease in phonon lifetime, collectively indicating strong defect-induced phonon scattering. As the vacancy concentration increases, phonon frequencies and lifetimes exhibit an approximately linear downward trend. Concurrently, the available phase space and anharmonic matrix elements associated with low-frequency phonon scattering are enhanced. These combined effects result in a rapid suppression of the lattice thermal conductivity and phonon mean free path, particularly in the low-frequency transport regime. This study not only avoids the theoretical limitations associated with calculating high-order anharmonic terms but also systematically quantifies the degradation of thermal conductivity with increasing vacancy concentration, thereby elucidating the microscopic mechanisms governing defect-induced anharmonicity and advancing the understanding of anharmonic lattice dynamics in β-Ga2O3.