2020 Fiscal Year Final Research Report
Exploration of the anharmonicity of phonons modes in molecular crystals with temperature-dependent and high-field terahertz spectroscopy and ab initio simulation
| Project/Area Number |
18K05034
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 32010:Fundamental physical chemistry-related
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| Research Institution | Kobe University |
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Principal Investigator |
Zhang Feng 神戸大学, 分子フォトサイエンス研究センター, 助手 (10773046)
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| Project Period (FY) |
2018-04-01 – 2021-03-31
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| Keywords | THz spectroscopoy / pure anharmonicity / quasi-harmonicity / temperature dependency / crystal disorder / THz intensity |
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| Outline of Final Research Achievements |
The PI has performed temperature-dependent THz measurements for alpha-lactose monohydrate, theophylline, and alpha-L-xylose. Interesting temperature dependencies have been observed in these systems. Quasi-harmonic calculations, which introduce an explicit dependence on unit-cell volume of THz modes and retain the harmonic expression for the Helmholtz free energy, have been performed to all three systems. The Quasi-harmonic results have been qualitatively explained the temperature-dependent frequency shifts for a few THz peaks. The correlation between the quasi-harmonicity and the nature of THz modes has been discussed. Due to the COVID-19 pandemic, the proposed high-field THz spectroscopic experiments have not been carried out. The PI expects to be able to complete this part of work after the pandemic. An interplay between the temperature-dependent and high-field terahertz spectroscopic measurements will lead to a more complete understanding of the anharmonicities of THz modes.
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| Free Research Field |
physical chemistry
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| Academic Significance and Societal Importance of the Research Achievements |
This research work gives an insight into the anharmonicity of THz modes, which may help to understand many related macroscopic properties such as thermal (or negative) expansion and heat conduction.
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