Gas element-vacancy complexes investigated by electron momentum distribution analysis using a combination of positron annihilation and first-principles calculations

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K03902
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 14020:Nuclear fusion-related
• Research Institution: Kyoto University
• Principal Investigator: Yabuuchi Atsushi 京都大学, 複合原子力科学研究所, 助教 (90551367)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 陽電子寿命 / 消滅ガンマ線ドップラー広がり / 電子運動量分布 / 第一原理計算 / 原子空孔 / 欠陥複合体

Outline of Final Research Achievements

The change in the positron lifetime of defect complexes (VXk) with multiple interstitial impurity atoms (X=H, C, N, O) bound with a vacancy in tungsten was investigated using first-principles calculations. It was found that the VH2, VC1, VN1, and VO1 complexes all exhibit a positron lifetime of around 170 ps. The Doppler broadening of the annihilation radiation spectra of these defect complexes was also calculated. It was shown that a shoulder appears around 16 mrad of electron momentum in the spectra of all defect complexes, making it difficult to distinguish the defect species. It was concluded that a combination of observation of the annealing behavior of defect complexes and calculation of the binding energy between vacancy and impurities is necessary to identify the species of these defect complexes.

Free Research Field

材料科学

Academic Significance and Societal Importance of the Research Achievements

核融合炉のプラズマ対向壁材料として期待されているタングステン中の原子空孔と侵入型不純物原子との相互作用、および不純物原子の空孔への結合が陽電子寿命や陽電子消滅ガンマ線ドップラー広がりに与える影響について第一原理計算を用いて調べた。タングステン中のそのような欠陥の種類を同定するためには欠陥のアニール挙動観察と不純物原子の空孔への結合エネルギー計算の併用が必要であることが示された。