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| Asıl Yazarlar: | , |
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| Materyal Türü: | Preprint |
| Baskı/Yayın Bilgisi: |
2024
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| Konular: | |
| Online Erişim: | https://arxiv.org/abs/2402.08087 |
| Etiketler: |
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| _version_ | 1866910549795667968 |
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| author | Jasrasaria, Dipti Berkelbach, Timothy C. |
| author_facet | Jasrasaria, Dipti Berkelbach, Timothy C. |
| contents | We use vibrational dynamical mean-field theory (VDMFT) to study the vibrational structure of type-I clathrate solids, specifically X$_8$Ga$_{16}$Ge$_{30}$, where X=Ba,Sr. These materials are cage-like chemical structures hosting loosely bound guest atoms, resulting in strong anharmonicity, short phonon lifetimes, and ultra-low thermal conductivities. Presenting the methodological developments necessary for this first application to three-dimensional, atomistic materials, we validate our approach through comparison to molecular dynamics simulations and show that VDMFT is extremely accurate at a fraction of the cost. Through the use of nonperturbative methods, we find that anharmonicity is dominated by four-phonon and higher-order scattering processes, and it causes rattler modes to shift up in frequency by 50% (10 cm$^{-1}$) and to have lifetimes of less than 1 ps; this behavior is not captured by traditional perturbation theory. Furthermore, we analyze the phonon self-energy and find that anharmonicity mixes guest rattling modes and cage acoustic modes, significantly changing the character of the harmonic phonons. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2402_08087 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Nonperturbative Simulation of Anharmonic Rattler Dynamics in Type-I Clathrates with Vibrational Dynamical Mean-Field Theory Jasrasaria, Dipti Berkelbach, Timothy C. Materials Science Chemical Physics We use vibrational dynamical mean-field theory (VDMFT) to study the vibrational structure of type-I clathrate solids, specifically X$_8$Ga$_{16}$Ge$_{30}$, where X=Ba,Sr. These materials are cage-like chemical structures hosting loosely bound guest atoms, resulting in strong anharmonicity, short phonon lifetimes, and ultra-low thermal conductivities. Presenting the methodological developments necessary for this first application to three-dimensional, atomistic materials, we validate our approach through comparison to molecular dynamics simulations and show that VDMFT is extremely accurate at a fraction of the cost. Through the use of nonperturbative methods, we find that anharmonicity is dominated by four-phonon and higher-order scattering processes, and it causes rattler modes to shift up in frequency by 50% (10 cm$^{-1}$) and to have lifetimes of less than 1 ps; this behavior is not captured by traditional perturbation theory. Furthermore, we analyze the phonon self-energy and find that anharmonicity mixes guest rattling modes and cage acoustic modes, significantly changing the character of the harmonic phonons. |
| title | Nonperturbative Simulation of Anharmonic Rattler Dynamics in Type-I Clathrates with Vibrational Dynamical Mean-Field Theory |
| topic | Materials Science Chemical Physics |
| url | https://arxiv.org/abs/2402.08087 |