Analysis and control of Heat transfer phenomenon in amorphous structure

Research Project

Project/Area Number	18K13697
Research Category	Grant-in-Aid for Early-Career Scientists
Allocation Type	Multi-year Fund
Review Section	Basic Section 19020:Thermal engineering-related
Research Institution	Tokyo University of Agriculture and Technology (2019) Tokyo University of Science (2018)
Principal Investigator	Hori Takuma 東京農工大学, 工学(系)研究科(研究院), 准教授 (50791513)
Project Period (FY)	2018-04-01 – 2020-03-31
Project Status	Completed (Fiscal Year 2019)
Budget Amount *help	¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000) Fiscal Year 2019: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000) Fiscal Year 2018: ¥2,730,000 (Direct Cost: ¥2,100,000、Indirect Cost: ¥630,000)
Keywords	熱伝導 / アモルファス / 分子動力学
Outline of Final Research Achievements	In order to understand and control the heat transfer in amorphous structures, a method for evaluating the interaction between phonon modes was developed. The molecular dynamics simulations, solving the time evolution of the trajectory of molecules under intermolecular potential, were utilized for the analysis. By using this method, one of the vibration modes in a crystal was excited and its relaxation process was evaluated to obtain the relaxation time. As a result, it was clarified that the relaxation curves of the excited modes exhibit exponential decay, which agrees with the perturbation theory of phonon scattering. It was also found that the developed method shows larger scattering rates compared with that from the perturbation theory. These results indicated that it is necessary to modify the relaxation time approximation in non-equilibrium systems.
Academic Significance and Societal Importance of the Research Achievements	近年の半導体デバイスの発展に伴い，コンピュータなどの情報機器の小型化や高性能化が進む一方で，排熱の問題がより深刻になっている．特に微細な構造における伝熱現象を明らかにするためにはフォノンの輸送問題を扱わなければならない．しかし，極めて温度差が小さい場合の解析は進む一方で，温度差が大きい，すなわち非平衡性が強い場合のフォノンの緩和現象は明らかになっていない．本研究によって，フォノンの緩和過程は非平衡性が大きい場合と平衡時で概ね一致するが，緩和時間が短くなることが分かった．