Cai, Qingan; Said, Ayman H.; Li, Chen
Monolayer-like Lattice Dynamics in Bulk WSe2 Journal Article Forthcoming
In: Materials Today Physics, Forthcoming.
BibTeX | Tags: 2D, anharmonicity, lattice dynamics, low dimension, phonon, selenide, transition metal dichalcogenides, X-ray scattering
@article{Cai2022,
title = {Monolayer-like Lattice Dynamics in Bulk WSe2},
author = {Qingan Cai and Ayman H. Said and Chen Li },
year = {2022},
date = {2022-10-10},
urldate = {2022-10-10},
journal = {Materials Today Physics},
keywords = {2D, anharmonicity, lattice dynamics, low dimension, phonon, selenide, transition metal dichalcogenides, X-ray scattering},
pubstate = {forthcoming},
tppubtype = {article}
}
Hou, Songrui; Sun, Bo; Tian, Fei; Cai, Qingan; Xu, Youming; Wang, Shanmin; Chen, Xi; Ren, Zhifeng; Li, Chen; Wilson, Richard B.
Thermal Conductivity of BAs under Pressure Journal Article
In: Advanced Electronic Materials, no. 2200017, 2022.
Abstract | Links | BibTeX | Tags: high pressure, phonon, thermal transport
@article{nokey,
title = {Thermal Conductivity of BAs under Pressure},
author = {Songrui Hou and Bo Sun and Fei Tian and Qingan Cai and Youming Xu and Shanmin Wang and Xi Chen and Zhifeng Ren and Chen Li and Richard B. Wilson},
url = {https://onlinelibrary.wiley.com/doi/10.1002/aelm.202200017},
doi = {10.1002/aelm.202200017},
year = {2022},
date = {2022-07-22},
urldate = {2022-07-22},
journal = {Advanced Electronic Materials},
number = {2200017},
abstract = {The thermal conductivity of boron arsenide (BAs) is believed to be influenced by phonon scattering selection rules due to its special phonon dispersion. Compression of BAs leads to significant changes in phonon dispersion, which allows for a test of first principles theories for how phonon dispersion affects three- and four-phonon scattering rates. This study reports the thermal conductivity of BAs from 0 to 30 GPa. Thermal conductivity vs. pressure of BAs is measured by time-domain thermoreflectance with a diamond anvil cell. In stark contrast to what is typical for nonmetallic crystals, BAs is observed to have a pressure independent thermal conductivity below 30 GPa. The thermal conductivity of nonmetallic crystals typically increases upon compression. The unusual pressure independence of BAs's thermal conductivity shows the important relationship between phonon dispersion properties and three- and four-phonon scattering rates.},
keywords = {high pressure, phonon, thermal transport},
pubstate = {published},
tppubtype = {article}
}
The thermal conductivity of boron arsenide (BAs) is believed to be influenced by phonon scattering selection rules due to its special phonon dispersion. Compression of BAs leads to significant changes in phonon dispersion, which allows for a test of first principles theories for how phonon dispersion affects three- and four-phonon scattering rates. This study reports the thermal conductivity of BAs from 0 to 30 GPa. Thermal conductivity vs. pressure of BAs is measured by time-domain thermoreflectance with a diamond anvil cell. In stark contrast to what is typical for nonmetallic crystals, BAs is observed to have a pressure independent thermal conductivity below 30 GPa. The thermal conductivity of nonmetallic crystals typically increases upon compression. The unusual pressure independence of BAs's thermal conductivity shows the important relationship between phonon dispersion properties and three- and four-phonon scattering rates.
Chen, Shuonan; Colema, Devin; Abernathy, Douglas L.; Banerjee, Arnab; Mangolini, Lorenzo; Li, Chen
Distinct Acoustic and Optical Phonon Dependences on Particle Size, Oxidation, and Temperature in Silicon Nanocrystals Journal Article
In: Joural of Physical Chemistry C, vol. 126, iss. 30, pp. 12704-12711, 2022.
Abstract | Links | BibTeX | Tags: confinement, nanoparticle, neutron scattering, phonon, photonics, silicon
@article{nokey,
title = {Distinct Acoustic and Optical Phonon Dependences on Particle Size, Oxidation, and Temperature in Silicon Nanocrystals},
author = {Shuonan Chen and Devin Colema and Douglas L. Abernathy and Arnab Banerjee and Lorenzo Mangolini and Chen Li},
url = {https://pubs.acs.org/doi/abs/10.1021/acs.jpcc.2c04246},
doi = {10.1021/acs.jpcc.2c04246},
year = {2022},
date = {2022-07-20},
journal = {Joural of Physical Chemistry C},
volume = {126},
issue = {30},
pages = {12704-12711},
abstract = {Phonon, as a momentum carrier, may play an important role in the photoluminescence of silicon nanocrystals. However, a systematic experimental study on phonon dynamics in spatially confined silicon systems remains limited. We used inelastic neutron scattering to investigate particle size, oxidation, and temperature effects on phonon dynamics of silicon nanocrystals by measuring phonon density of states of 12 and 50 nm silicon nanocrystals with several oxidation levels at different temperatures. We showed that the lattice vibrations of large silicon nanocrystals and bulk silicon are substantially different. We found that transverse acoustic phonon modes have much stronger dependences on particle size, oxidation, and temperature than optical phonon modes. We showed that the changes in phonon dynamics have the largest effect on vibrational entropy and free energy of silicon nanocrystals at intermediate temperatures. Our results shed light on phonon dynamics of silicon-based functional nanomaterials and will facilitate further investigations of electron\textendashphonon interactions in spatially confined silicon systems.},
keywords = {confinement, nanoparticle, neutron scattering, phonon, photonics, silicon},
pubstate = {published},
tppubtype = {article}
}
Phonon, as a momentum carrier, may play an important role in the photoluminescence of silicon nanocrystals. However, a systematic experimental study on phonon dynamics in spatially confined silicon systems remains limited. We used inelastic neutron scattering to investigate particle size, oxidation, and temperature effects on phonon dynamics of silicon nanocrystals by measuring phonon density of states of 12 and 50 nm silicon nanocrystals with several oxidation levels at different temperatures. We showed that the lattice vibrations of large silicon nanocrystals and bulk silicon are substantially different. We found that transverse acoustic phonon modes have much stronger dependences on particle size, oxidation, and temperature than optical phonon modes. We showed that the changes in phonon dynamics have the largest effect on vibrational entropy and free energy of silicon nanocrystals at intermediate temperatures. Our results shed light on phonon dynamics of silicon-based functional nanomaterials and will facilitate further investigations of electron–phonon interactions in spatially confined silicon systems.
Su, Yaokun; Smith, Hillary L.; Stone, Matthew B.; Abernathy, Douglas L.; Lumsden, Mark D.; Adams, Carl P.; Li, Chen
Frustration-induced diffusive scattering anomaly and dimension change in FeGe2 Journal Article
In: Physical Review B, vol. 106, no. 024406, 2022.
Abstract | Links | BibTeX | Tags: frustration, magnetism, magnon-phonon, neutron, neutron scattering, phonon
@article{nokey,
title = {Frustration-induced diffusive scattering anomaly and dimension change in FeGe2},
author = {Yaokun Su and Hillary L. Smith and Matthew B. Stone and Douglas L. Abernathy and Mark D. Lumsden and Carl P. Adams and Chen Li},
url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.106.024406},
doi = {10.1103/PhysRevB.106.024406},
year = {2022},
date = {2022-07-11},
urldate = {2022-07-11},
journal = {Physical Review B},
volume = {106},
number = {024406},
abstract = {Magnetic frustration, arising from the competition of exchange interactions, has received great attention because of its relevance to exotic quantum phenomena in materials. In the current work, we report an unusual checkerboard-shaped scattering anomaly in FeGe2, far from the known incommensurate magnetic satellite peaks, by inelastic neutron scattering. More surprisingly, such phenomenon appears as spin dynamics at low temperature, but it becomes prominent above N\'{e}el transition as elastic scattering. A model Hamiltonian that includes an intraplane next-nearest neighbor was proposed and such anomaly is attributed to the near-perfect magnetic frustration and the emergence of unexpected two-dimensional magnetic order in the quasi-one-dimensional FeGe2.},
keywords = {frustration, magnetism, magnon-phonon, neutron, neutron scattering, phonon},
pubstate = {published},
tppubtype = {article}
}
Magnetic frustration, arising from the competition of exchange interactions, has received great attention because of its relevance to exotic quantum phenomena in materials. In the current work, we report an unusual checkerboard-shaped scattering anomaly in FeGe2, far from the known incommensurate magnetic satellite peaks, by inelastic neutron scattering. More surprisingly, such phenomenon appears as spin dynamics at low temperature, but it becomes prominent above Néel transition as elastic scattering. A model Hamiltonian that includes an intraplane next-nearest neighbor was proposed and such anomaly is attributed to the near-perfect magnetic frustration and the emergence of unexpected two-dimensional magnetic order in the quasi-one-dimensional FeGe2.
Liu, Junyan; Strobel, Timothy A.; Zhang, Haidong; Abernathy, Doug; Li, Chen; Hong, Jiawang
Significant phase-space-driven thermal transport suppression in BC8 silicon Journal Article
In: Materials Today Physics, vol. 21, pp. 100566, 2021.
Abstract | Links | BibTeX | Tags: anharmonicity, lattice dynamics, phonon, thermal transport
@article{nokey,
title = {Significant phase-space-driven thermal transport suppression in BC8 silicon},
author = {Junyan Liu and Timothy A. Strobel and Haidong Zhang and Doug Abernathy and Chen Li and Jiawang Hong},
url = {https://www.sciencedirect.com/science/article/pii/S2542529321002273?dgcid=author},
doi = {10.1016/j.mtphys.2021.100566},
year = {2021},
date = {2021-10-29},
journal = {Materials Today Physics},
volume = {21},
pages = {100566},
abstract = {The BC8 silicon allotrope has a lattice thermal conductivity 1\textendash2 orders of magnitude lower than that of diamond-cubic silicon. In the current work, the phonon density of states, phonon dispersion, and lattice thermal conductivity are investigated by inelastic neutron scattering measurements and first-principles calculations. Flat phonon bands are found to play a critical role in the reduction of lattice thermal conductivity in BC8\textendashSi. Such bands in the low-energy range enhance the phonon scattering between acoustic and low-energy optical phonons, while bands in the intermediate-energy range act as a scattering bridge between the high- and low-energy optical phonons. They significantly enlarge the phonon-phonon scattering phase space and reduces the lattice thermal conductivity in this novel silicon allotrope. This work provides insights into the significant reduction of the lattice thermal conductivity in BC8\textendashSi, thus expanding the understanding of novel silicon allotropes and their development for electronic devices.},
keywords = {anharmonicity, lattice dynamics, phonon, thermal transport},
pubstate = {published},
tppubtype = {article}
}
The BC8 silicon allotrope has a lattice thermal conductivity 1–2 orders of magnitude lower than that of diamond-cubic silicon. In the current work, the phonon density of states, phonon dispersion, and lattice thermal conductivity are investigated by inelastic neutron scattering measurements and first-principles calculations. Flat phonon bands are found to play a critical role in the reduction of lattice thermal conductivity in BC8–Si. Such bands in the low-energy range enhance the phonon scattering between acoustic and low-energy optical phonons, while bands in the intermediate-energy range act as a scattering bridge between the high- and low-energy optical phonons. They significantly enlarge the phonon-phonon scattering phase space and reduces the lattice thermal conductivity in this novel silicon allotrope. This work provides insights into the significant reduction of the lattice thermal conductivity in BC8–Si, thus expanding the understanding of novel silicon allotropes and their development for electronic devices.
Wei, B.; Cai, Q.; Sun, Q.; Su, Y.; Said, A. H.; Abernathy, D. L.; Hong, J.; Li, C.
Matryoshka Phonon Twining in a-GaN Journal Article
In: Communications Physics, vol. 4, no. 227, 2021.
Abstract | Links | BibTeX | Tags: lattice expansion, metal-insulator transition, phonon, thermal transport
@article{Li2021,
title = {Matryoshka Phonon Twining in a-GaN},
author = {B. Wei and Q. Cai and Q. Sun and Y. Su and A. H. Said and D. L. Abernathy and J. Hong and
C. Li},
url = {https://www.nature.com/articles/s42005-021-00727-9},
doi = {10.1038/s42005-021-00727-9},
year = {2021},
date = {2021-10-12},
urldate = {2021-10-12},
journal = {Communications Physics},
volume = {4},
number = {227},
abstract = {Understanding lattice dynamics is crucial for effective thermal management in electronic devices because phonons dominate thermal transport in most semiconductors. α-GaN has become a focus of interest as one of the most important third-generation power semiconductors, however, the knowledge on its phonon dynamics remains limited. Here we show a Matryoshka phonon dispersion of α-GaN with the complementary inelastic X-ray and neutron scattering techniques and the first-principles calculations. Such Matryoshka twinning throughout the basal plane of the reciprocal space is demonstrated to amplify the anharmonicity of the related phonons through creating abundant three-phonon scattering channels and cutting the lifetime of affected modes by more than 50%. Such phonon topology contributes to reducing the in-plane thermal transport, thus the anisotropic thermal conductivity of α-GaN. The results not only have implications for engineering the thermal performance of α-GaN, but also offer valuable insights on the role of anomalous phonon topology in thermal transport of other technically semiconductors.},
keywords = {lattice expansion, metal-insulator transition, phonon, thermal transport},
pubstate = {published},
tppubtype = {article}
}
Understanding lattice dynamics is crucial for effective thermal management in electronic devices because phonons dominate thermal transport in most semiconductors. α-GaN has become a focus of interest as one of the most important third-generation power semiconductors, however, the knowledge on its phonon dynamics remains limited. Here we show a Matryoshka phonon dispersion of α-GaN with the complementary inelastic X-ray and neutron scattering techniques and the first-principles calculations. Such Matryoshka twinning throughout the basal plane of the reciprocal space is demonstrated to amplify the anharmonicity of the related phonons through creating abundant three-phonon scattering channels and cutting the lifetime of affected modes by more than 50%. Such phonon topology contributes to reducing the in-plane thermal transport, thus the anisotropic thermal conductivity of α-GaN. The results not only have implications for engineering the thermal performance of α-GaN, but also offer valuable insights on the role of anomalous phonon topology in thermal transport of other technically semiconductors.
Cai, Qingan; McIntire, Michael; Daemen, Luke L.; Li, Chen; Chronister, Eric L.
Pressure- and temperature-dependent inelastic neutron scattering study of the phase transition and phonon lattice dynamics in para-terphenyl Journal Article
In: Physical Chemistry Chemical Physics, vol. 23, pp. 8792, 2021.
Abstract | Links | BibTeX | Tags: high pressure, phonon, Raman
@article{Cai2021,
title = {Pressure- and temperature-dependent inelastic neutron scattering study of the phase transition and phonon lattice dynamics in para-terphenyl},
author = {Qingan Cai and Michael McIntire and Luke L. Daemen and Chen Li and Eric L. Chronister},
url = {https://pubs.rsc.org/en/content/articlelanding/2021/cp/d1cp00190f#!divAbstract},
doi = {10.1039/D1CP00190F},
year = {2021},
date = {2021-03-24},
journal = {Physical Chemistry Chemical Physics},
volume = {23},
pages = {8792},
abstract = {Inelastic neutron scattering has been performed on para-terphenyl at temperatures from 10 to 200 K and under pressures from the ambient pressure to 1.51 kbar. The temperature dependence of phonons, especially low-frequency librational bands, indicates strong anharmonic phonon dynamics. The pressure- and temperature-dependence of the phonon modes suggest a lack of phase transition in the region of 0\textendash1.51 kbar and 10\textendash30 K. Additionally, the overall lattice dynamics remains similar up to 200 K under the ambient pressure. The results suggest that the boundary between the ordered triclinic phase and the third solid phase, reported at lower temperatures and higher pressures, is out of the pressure and temperature range of this study.},
keywords = {high pressure, phonon, Raman},
pubstate = {published},
tppubtype = {article}
}
Inelastic neutron scattering has been performed on para-terphenyl at temperatures from 10 to 200 K and under pressures from the ambient pressure to 1.51 kbar. The temperature dependence of phonons, especially low-frequency librational bands, indicates strong anharmonic phonon dynamics. The pressure- and temperature-dependence of the phonon modes suggest a lack of phase transition in the region of 0–1.51 kbar and 10–30 K. Additionally, the overall lattice dynamics remains similar up to 200 K under the ambient pressure. The results suggest that the boundary between the ordered triclinic phase and the third solid phase, reported at lower temperatures and higher pressures, is out of the pressure and temperature range of this study.
Kim, D. S.; Hellman, O.; Shulumba, N.; Saunders, C. N.; Lin, J. Y. Y.; Smith, H. L.; Herriman, J. E.; Niedziela, J. L.; Abernathy, D. L.; Li, C. W.; Fultz, B.
Temperature-dependent phonon lifetimes and thermal conductivity of silicon by inelastic neutron scattering and ab initio calculations Journal Article
In: Phys. Rev. B, vol. 102, pp. 174311, 2020.
Abstract | Links | BibTeX | Tags: lattice, lifetime, phonon
@article{Fultz2020,
title = {Temperature-dependent phonon lifetimes and thermal conductivity of silicon by inelastic neutron scattering and ab initio calculations},
author = {D. S. Kim and O. Hellman and N. Shulumba and C. N. Saunders and J. Y. Y. Lin and H. L. Smith and J. E. Herriman and J. L. Niedziela and D. L. Abernathy and C. W. Li and B. Fultz},
url = {https://doi.org/10.1103/PhysRevB.102.174311},
doi = {10.1103/PhysRevB.102.174311},
year = {2020},
date = {2020-11-16},
journal = {Phys. Rev. B},
volume = {102},
pages = {174311},
abstract = {Inelastic neutron scattering on a single crystal of silicon was performed at temperatures from 100 to 1500 K. These experimental data were reduced to obtain phonon spectral intensity at all wave vectors Q and frequencies ω in the first Brillouin zone. Thermal broadenings of the phonon peaks were obtained by fitting and by calculating with an iterative ab initio method that uses thermal atom displacements on an ensemble of superlattices. Agreement between the calculated and experimental broadenings was good, with possible discrepancies at the highest temperatures. Distributions of phonon widths versus phonon energy had similar shapes for computation and experiment. These distributions grew with temperature but maintained similar shapes. Parameters from the ab initio calculations were used to obtain the thermal conductivity from the Boltzmann transport equation, which was in good agreement with experimental data. Despite the high group velocities of longitudinal acoustic phonons, their shorter lifetimes reduced their contribution to the thermal conductivity, which was dominated by transverse acoustic modes.},
keywords = {lattice, lifetime, phonon},
pubstate = {published},
tppubtype = {article}
}
Inelastic neutron scattering on a single crystal of silicon was performed at temperatures from 100 to 1500 K. These experimental data were reduced to obtain phonon spectral intensity at all wave vectors Q and frequencies ω in the first Brillouin zone. Thermal broadenings of the phonon peaks were obtained by fitting and by calculating with an iterative ab initio method that uses thermal atom displacements on an ensemble of superlattices. Agreement between the calculated and experimental broadenings was good, with possible discrepancies at the highest temperatures. Distributions of phonon widths versus phonon energy had similar shapes for computation and experiment. These distributions grew with temperature but maintained similar shapes. Parameters from the ab initio calculations were used to obtain the thermal conductivity from the Boltzmann transport equation, which was in good agreement with experimental data. Despite the high group velocities of longitudinal acoustic phonons, their shorter lifetimes reduced their contribution to the thermal conductivity, which was dominated by transverse acoustic modes.
Niedziela, J. L.; Bansal, D.; Ding, J.; Lanigan-Atkins, T.; Li, Chen; May, A. F.; Wang, H.; Lin, J. Y. Y.; Abernathy, D. L.; Ehlers, G.; Huq, A.; Parshall, D.; Lynn, J. W.; Delaire, O.
Controlling phonon lifetimes via sublattice disordering in AgBiSe2 Journal Article
In: Phys. Rev. Materials, vol. 4, pp. 105402, 2020.
Abstract | Links | BibTeX | Tags: lattice dynamics, phonon, thermal transport
@article{Delaire2020,
title = {Controlling phonon lifetimes via sublattice disordering in AgBiSe2},
author = {J. L. Niedziela and D. Bansal and J. Ding and T. Lanigan-Atkins and Chen Li and A. F. May and H. Wang and J. Y. Y. Lin and D. L. Abernathy and G. Ehlers and A. Huq and D. Parshall and J. W. Lynn and O. Delaire},
url = {https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.4.105402},
doi = {10.1103/PhysRevMaterials.4.105402},
year = {2020},
date = {2020-08-04},
journal = {Phys. Rev. Materials},
volume = {4},
pages = {105402},
abstract = {Understanding and controlling microscopic heat transfer mechanisms in solids is critical to material design in numerous technological applications. Yet, the current understanding of thermal transport in semiconductors and insulators is limited by the difficulty in directly measuring individual phonon lifetimes and mean free paths, and studying their dependence on the microscopic state of the material. Here we report our measurements of microscopic phonon scattering rates in AgBiSe2, which exhibits a controllable, reversible change directly linked to microstructure evolution near a reversible structural phase transition, that directly impacts the thermal conductivity. We demonstrate a steplike doubling of phonon scattering rates resultant from the cation disordering at the structural transition. To rationalize the neutron scattering data, we leverage a stepwise approach to account for alterations to the thermal conductivity that are imparted by distinct scattering mechanisms. These results highlight the potential of tunable microstructures housed in a stable crystal matrix to provide a practical route to tailor phonon scattering to optimize thermal transport properties.},
keywords = {lattice dynamics, phonon, thermal transport},
pubstate = {published},
tppubtype = {article}
}
Understanding and controlling microscopic heat transfer mechanisms in solids is critical to material design in numerous technological applications. Yet, the current understanding of thermal transport in semiconductors and insulators is limited by the difficulty in directly measuring individual phonon lifetimes and mean free paths, and studying their dependence on the microscopic state of the material. Here we report our measurements of microscopic phonon scattering rates in AgBiSe2, which exhibits a controllable, reversible change directly linked to microstructure evolution near a reversible structural phase transition, that directly impacts the thermal conductivity. We demonstrate a steplike doubling of phonon scattering rates resultant from the cation disordering at the structural transition. To rationalize the neutron scattering data, we leverage a stepwise approach to account for alterations to the thermal conductivity that are imparted by distinct scattering mechanisms. These results highlight the potential of tunable microstructures housed in a stable crystal matrix to provide a practical route to tailor phonon scattering to optimize thermal transport properties.
Sun, Qiyang; Li, Chen W.
Exploring nanoscale heat transport via neutron scattering Book Chapter
In: Liao, Bolin (Ed.): pp. 11-1~14, 2020, ISBN: 978-0-7503-1736-8.
Abstract | Links | BibTeX | Tags: lattice dynamics, phonon, thermal transport
@inbook{Sun2020,
title = {Exploring nanoscale heat transport via neutron scattering},
author = {Qiyang Sun and Chen W. Li},
editor = {Bolin Liao},
url = {https://iopscience.iop.org/book/978-0-7503-1738-2},
isbn = {978-0-7503-1736-8},
year = {2020},
date = {2020-03-01},
pages = {11-1~14},
abstract = {Nanoscale Energy Transport
Emerging phenomena, methods and applications
This book brings together leading names in the field of nanoscale energy transport to provide a comprehensive and insightful review of this developing topic. The text covers new developments in the scientific basis and the practical relevance of nanoscale energy transport, highlighting the emerging effects at the nanoscale that qualitatively differ from those at the macroscopic scale. Throughout the book, microscopic energy carriers are discussed, including photons, electrons and magnons. State-of-the-art computational and experimental nanoscale energy transport methods are reviewed, and a broad range of materials system topics are considered, from interfaces and molecular junctions to nanostructured bulk materials. Nanoscale Energy Transport is a valuable reference for researchers in physics, materials, mechanical and electrical engineering, and it provides an excellent resource for graduate students.},
keywords = {lattice dynamics, phonon, thermal transport},
pubstate = {published},
tppubtype = {inbook}
}
Nanoscale Energy Transport
Emerging phenomena, methods and applications
This book brings together leading names in the field of nanoscale energy transport to provide a comprehensive and insightful review of this developing topic. The text covers new developments in the scientific basis and the practical relevance of nanoscale energy transport, highlighting the emerging effects at the nanoscale that qualitatively differ from those at the macroscopic scale. Throughout the book, microscopic energy carriers are discussed, including photons, electrons and magnons. State-of-the-art computational and experimental nanoscale energy transport methods are reviewed, and a broad range of materials system topics are considered, from interfaces and molecular junctions to nanostructured bulk materials. Nanoscale Energy Transport is a valuable reference for researchers in physics, materials, mechanical and electrical engineering, and it provides an excellent resource for graduate students.
Emerging phenomena, methods and applications
This book brings together leading names in the field of nanoscale energy transport to provide a comprehensive and insightful review of this developing topic. The text covers new developments in the scientific basis and the practical relevance of nanoscale energy transport, highlighting the emerging effects at the nanoscale that qualitatively differ from those at the macroscopic scale. Throughout the book, microscopic energy carriers are discussed, including photons, electrons and magnons. State-of-the-art computational and experimental nanoscale energy transport methods are reviewed, and a broad range of materials system topics are considered, from interfaces and molecular junctions to nanostructured bulk materials. Nanoscale Energy Transport is a valuable reference for researchers in physics, materials, mechanical and electrical engineering, and it provides an excellent resource for graduate students.
He, L.; Li, Chen W.; Hamilton, W. A.; Hong, T.; Tong, X.; Winn, B. L.; Crow, L.; Bailey, K.; Gallego, N. C.
Anomalous neutron scattering ‘halo’ observed in highly oriented pyrolytic graphite Journal Article
In: Journal of Applied Cyrstallography, vol. 52, no. 2, pp. 296-303, 2019.
Abstract | Links | BibTeX | Tags: graphite, neutron scattering, phonon
@article{He2019,
title = {Anomalous neutron scattering ‘halo’ observed in highly oriented pyrolytic graphite},
author = {L. He and Chen W. Li and W.A. Hamilton and T. Hong and X. Tong and B.L. Winn and L. Crow and K. Bailey and N.C. Gallego},
url = {https://onlinelibrary.wiley.com/iucr/doi/10.1107/S1600576719001110},
doi = {10.1107/S1600576719001110},
year = {2019},
date = {2019-03-05},
journal = {Journal of Applied Cyrstallography},
volume = {52},
number = {2},
pages = {296-303},
abstract = {Highly oriented pyrolytic graphite (HOPG) has been used as monochromators, analyzers and filters at neutron and X-ray scattering facilities for more than half a century. Interesting questions remain. In this work, the first observation of anomalous neutron ‘halo’ scattering of HOPG is reported. The scattering projects a ring onto the detector with a half-cone angle of 12.4, which surprisingly persists to incident neutron wavelengths far beyond the Bragg cutoff for graphite (6.71 A ̊ ). At longer wavelengths the ring is clearly a doublet with a splitting roughly proportional to wavelength. Sample tilting leads to the shift of the ring, which is wavelength dependent with longer wavelengths providing a smaller difference between the ring shift and the sample tilting. The ring broadens and weakens with decreasing HOPG quality. The lattice dynamics of graphite play a role in causing the scattering ring, as shown by the fact that the ring vanishes once the sample is cooled to 30 K. A possible interpretation by multiple scattering including elastic and inelastic processes is proposed.},
keywords = {graphite, neutron scattering, phonon},
pubstate = {published},
tppubtype = {article}
}
Highly oriented pyrolytic graphite (HOPG) has been used as monochromators, analyzers and filters at neutron and X-ray scattering facilities for more than half a century. Interesting questions remain. In this work, the first observation of anomalous neutron ‘halo’ scattering of HOPG is reported. The scattering projects a ring onto the detector with a half-cone angle of 12.4, which surprisingly persists to incident neutron wavelengths far beyond the Bragg cutoff for graphite (6.71 A ̊ ). At longer wavelengths the ring is clearly a doublet with a splitting roughly proportional to wavelength. Sample tilting leads to the shift of the ring, which is wavelength dependent with longer wavelengths providing a smaller difference between the ring shift and the sample tilting. The ring broadens and weakens with decreasing HOPG quality. The lattice dynamics of graphite play a role in causing the scattering ring, as shown by the fact that the ring vanishes once the sample is cooled to 30 K. A possible interpretation by multiple scattering including elastic and inelastic processes is proposed.
Smith, Hillary L.; Shen, Yang; Kim, Dennis S.; Yang, Fred C.; Adams, C. P.; Li, Chen W.; Abernathy, D. L.; Stone, M. B.; Fultz, B.
Temperature dependence of phonons in FeGe2 Journal Article
In: Physical Review Materials, vol. 2, pp. 103602, 2018.
Abstract | Links | BibTeX | Tags: anharmonicity, high temperature, lattice expansion, magnetism, phonon, vibrational entropy
@article{Smith2018,
title = {Temperature dependence of phonons in FeGe2},
author = {Hillary L. Smith and Yang Shen and Dennis S. Kim and Fred C. Yang and C.P. Adams and Chen W. Li and D.L. Abernathy and M.B. Stone and B. Fultz},
url = {https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.2.103602},
doi = {10.1103/PhysRevMaterials.2.103602},
year = {2018},
date = {2018-10-09},
journal = {Physical Review Materials},
volume = {2},
pages = {103602},
abstract = {Inelastic neutron scattering was used to measure phonon dispersions in a single crystal of FeGe2 with the C16 structure at 300, 500, and 635 K. Phonon densities of states (DOS) were also measured on polycrystalline FeGe2 from 325 to 1050 K, and the Fe partial DOS was obtained from polycrystalline
57 FeGe2 at 300 K using nuclear resonant inelastic x-ray scattering. The dominant feature in the temperature dependence of the phonon spectrum is thermal broadening of high-energy modes. The energy shifts of the low- and high-energy parts of the spectrum were almost the same. DFT calculations performed with the quasiharmonic approximation gave results in moderate agreement with the experimental thermal energy shifts, although the isobaric Gr\"{u}neisen parameter calculated from the quasiharmonic model was smaller than that from measurements. The thermal broadening of the phonon spectrum and dispersions, especially at high energies, indicates a cubic anharmonicity to second order that should also induce phonon shifts. We show that different anharmonic contributions cancel out, giving average phonon shifts in moderate agreement to calculations with the quasiharmonic approximation. The different parts of the large phonon contribution to the entropy are separated for FeGe2, showing modest but interpretable anharmonic contributions.},
keywords = {anharmonicity, high temperature, lattice expansion, magnetism, phonon, vibrational entropy},
pubstate = {published},
tppubtype = {article}
}
Inelastic neutron scattering was used to measure phonon dispersions in a single crystal of FeGe2 with the C16 structure at 300, 500, and 635 K. Phonon densities of states (DOS) were also measured on polycrystalline FeGe2 from 325 to 1050 K, and the Fe partial DOS was obtained from polycrystalline
57 FeGe2 at 300 K using nuclear resonant inelastic x-ray scattering. The dominant feature in the temperature dependence of the phonon spectrum is thermal broadening of high-energy modes. The energy shifts of the low- and high-energy parts of the spectrum were almost the same. DFT calculations performed with the quasiharmonic approximation gave results in moderate agreement with the experimental thermal energy shifts, although the isobaric Grüneisen parameter calculated from the quasiharmonic model was smaller than that from measurements. The thermal broadening of the phonon spectrum and dispersions, especially at high energies, indicates a cubic anharmonicity to second order that should also induce phonon shifts. We show that different anharmonic contributions cancel out, giving average phonon shifts in moderate agreement to calculations with the quasiharmonic approximation. The different parts of the large phonon contribution to the entropy are separated for FeGe2, showing modest but interpretable anharmonic contributions.
57 FeGe2 at 300 K using nuclear resonant inelastic x-ray scattering. The dominant feature in the temperature dependence of the phonon spectrum is thermal broadening of high-energy modes. The energy shifts of the low- and high-energy parts of the spectrum were almost the same. DFT calculations performed with the quasiharmonic approximation gave results in moderate agreement with the experimental thermal energy shifts, although the isobaric Grüneisen parameter calculated from the quasiharmonic model was smaller than that from measurements. The thermal broadening of the phonon spectrum and dispersions, especially at high energies, indicates a cubic anharmonicity to second order that should also induce phonon shifts. We show that different anharmonic contributions cancel out, giving average phonon shifts in moderate agreement to calculations with the quasiharmonic approximation. The different parts of the large phonon contribution to the entropy are separated for FeGe2, showing modest but interpretable anharmonic contributions.
Smith, H L; Li, Chen W; Hoff, A; Garrett, G R; Kim, D S; Yang, F C; Lucas, M S; Swan-Wood, T; Lin, J Y Y; Stone, M B; Abernathy, D L; Demetriou, M D; Fultz, B
Separating the configurational and vibrational entropy contributions in metallic glasses Journal Article
In: Nature Physics, vol. 13, no. 9, pp. 900-905, 2017.
Links | BibTeX | Tags: metallic glass, neutron, phase transition, phonon, thermodynamics, vibrational entropy
@article{Smith:2017goa,
title = {Separating the configurational and vibrational entropy contributions in metallic glasses},
author = {H L Smith and Chen W Li and A Hoff and G R Garrett and D S Kim and F C Yang and M S Lucas and T Swan-Wood and J Y Y Lin and M B Stone and D L Abernathy and M D Demetriou and B Fultz},
url = {http://www.nature.com/doifinder/10.1038/nphys4142},
doi = {10.1038/nphys4142},
year = {2017},
date = {2017-01-01},
journal = {Nature Physics},
volume = {13},
number = {9},
pages = {900-905},
keywords = {metallic glass, neutron, phase transition, phonon, thermodynamics, vibrational entropy},
pubstate = {published},
tppubtype = {article}
}
Shen, Yang; Li, Chen W.; Tang, Xiaoli; Smith, Hillary L.; Fultz, B.
honon anharmonicity and components of the entropy in palladium and platinum Journal Article
In: Physical Review B, vol. 93, pp. 214303, 2016.
Abstract | Links | BibTeX | Tags: anharmonicity, neutron, phonon, vibrational entropy
@article{Shen2016,
title = {honon anharmonicity and components of the entropy in palladium and platinum},
author = {Shen, Yang and Li, Chen W. and Tang, Xiaoli and Smith, Hillary L. and Fultz, B.},
url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.214303},
doi = {10.1103/PhysRevB.93.214303},
year = {2016},
date = {2016-06-07},
journal = {Physical Review B},
volume = {93},
pages = {214303},
abstract = {Inelastic neutron scattering was used to measure the phonon density of states in fcc palladium and platinum metal at temperatures from 7 K to 1576 K. Both phonon-phonon interactions and electron-phonon interactions were calculated by methods based on density functional theory (DFT) and were consistent with the measured shifts and broadenings of phonons with temperature. Unlike the longitudinal modes, the characteristic transverse modes had a nonlinear dependence on temperature owing to the requirement for a population of thermal phonons for upscattering. Kohn anomalies were observed in the measurements at low temperature and were reproduced by calculations based on DFT. Contributions to the entropy from phonons and electrons were assessed and summed to obtain excellent agreement with prior calorimetric data. The entropy from thermal expansion is positive for both phonons and electrons but larger for phonons. The anharmonic phonon entropy is negative in Pt, but in Pd it changes from positive to negative with increasing temperature. Owing to the position of the Fermi level on the electronic DOS, the electronic entropy was sensitive to the adiabatic electron-phonon interaction in both Pd and Pt. The adiabatic EPI depended strongly on thermal atom displacements.},
keywords = {anharmonicity, neutron, phonon, vibrational entropy},
pubstate = {published},
tppubtype = {article}
}
Inelastic neutron scattering was used to measure the phonon density of states in fcc palladium and platinum metal at temperatures from 7 K to 1576 K. Both phonon-phonon interactions and electron-phonon interactions were calculated by methods based on density functional theory (DFT) and were consistent with the measured shifts and broadenings of phonons with temperature. Unlike the longitudinal modes, the characteristic transverse modes had a nonlinear dependence on temperature owing to the requirement for a population of thermal phonons for upscattering. Kohn anomalies were observed in the measurements at low temperature and were reproduced by calculations based on DFT. Contributions to the entropy from phonons and electrons were assessed and summed to obtain excellent agreement with prior calorimetric data. The entropy from thermal expansion is positive for both phonons and electrons but larger for phonons. The anharmonic phonon entropy is negative in Pt, but in Pd it changes from positive to negative with increasing temperature. Owing to the position of the Fermi level on the electronic DOS, the electronic entropy was sensitive to the adiabatic electron-phonon interaction in both Pd and Pt. The adiabatic EPI depended strongly on thermal atom displacements.
Bansal, D; Hong, J; Li, Chen W; May, A F; Porter, W; Hu, M Y; Abernathy, D L; Delaire, O
Phonon anharmonicity and negative thermal expansion in SnSe Journal Article
In: Physical Review B, vol. 94, no. 5, pp. 054307, 2016.
Links | BibTeX | Tags: neutron, NTE, phonon, selenide, thermodynamics, thermoelectric
@article{Bansal:2016hd,
title = {Phonon anharmonicity and negative thermal expansion in SnSe},
author = {D Bansal and J Hong and Chen W Li and A F May and W Porter and M Y Hu and D L Abernathy and O Delaire},
url = {https://link.aps.org/doi/10.1103/PhysRevB.94.054307},
doi = {10.1103/PhysRevB.94.054307},
year = {2016},
date = {2016-01-01},
journal = {Physical Review B},
volume = {94},
number = {5},
pages = {054307},
keywords = {neutron, NTE, phonon, selenide, thermodynamics, thermoelectric},
pubstate = {published},
tppubtype = {article}
}
Li, Chen W; Smith, H L; Lan, T; Niedziela, J L; Munoz, J A; Keith, J B; Mauger, L; Abernathy, D L; Fultz, B
Phonon anharmonicity of monoclinic zirconia and yttrium-stabilized zirconia Journal Article
In: Physical Review B, vol. 91, no. 14, pp. 5563, 2015.
Links | BibTeX | Tags: anharmonicity, oxide, phonon
@article{li_phonon_2015,
title = {Phonon anharmonicity of monoclinic zirconia and yttrium-stabilized zirconia},
author = {Chen W Li and H L Smith and T Lan and J L Niedziela and J A Munoz and J B Keith and L Mauger and D L Abernathy and B Fultz},
url = {https://link.aps.org/doi/10.1103/PhysRevB.91.144302},
doi = {10.1103/PhysRevB.91.144302},
year = {2015},
date = {2015-04-01},
journal = {Physical Review B},
volume = {91},
number = {14},
pages = {5563},
keywords = {anharmonicity, oxide, phonon},
pubstate = {published},
tppubtype = {article}
}
Delaire, O; Al-Qasir, I I; May, A F; Li, Chen W; Sales, B C; Niedziela, J L; Ma, J; Matsuda, M; Abernathy, D L; Berlijn, T
Heavy-impurity resonance, hybridization, and phonon spectral functions in Fe1−xMxSi (M=Ir, Os) Journal Article
In: Physical Review B, vol. 91, no. 9, pp. 784, 2015.
Links | BibTeX | Tags: anharmonicity, lattice dynamics, phonon
@article{delaire_heavy-impurity_2015,
title = {Heavy-impurity resonance, hybridization, and phonon spectral functions in Fe1−xMxSi (M=Ir, Os)},
author = {O Delaire and I I Al-Qasir and A F May and Chen W Li and B C Sales and J L Niedziela and J Ma and M Matsuda and D L Abernathy and T Berlijn},
url = {https://link.aps.org/doi/10.1103/PhysRevB.91.094307},
doi = {10.1103/PhysRevB.91.094307},
year = {2015},
date = {2015-03-01},
journal = {Physical Review B},
volume = {91},
number = {9},
pages = {784},
keywords = {anharmonicity, lattice dynamics, phonon},
pubstate = {published},
tppubtype = {article}
}
Lan, T; Li, Chen W; Hellman, O; Kim, D S; Munoz, J A; Smith, H L; Abernathy, D L; Fultz, B
Phonon quarticity induced by changes in phonon-tracked hybridization during lattice expansion and its stabilization of rutile TiO2 Journal Article
In: Physical Review B, vol. 92, no. 5, 2015.
Links | BibTeX | Tags: anharmonicity, lattice, lattice expansion, oxide, phonon
@article{Lan:2015bs,
title = {Phonon quarticity induced by changes in phonon-tracked hybridization during lattice expansion and its stabilization of rutile TiO2},
author = {T Lan and Chen W Li and O Hellman and D S Kim and J A Munoz and H L Smith and D L Abernathy and B Fultz},
url = {http://link.aps.org/doi/10.1103/PhysRevB.92.054304},
doi = {10.1103/PhysRevB.92.054304},
year = {2015},
date = {2015-01-01},
journal = {Physical Review B},
volume = {92},
number = {5},
keywords = {anharmonicity, lattice, lattice expansion, oxide, phonon},
pubstate = {published},
tppubtype = {article}
}
Bansal, D; Li, Chen W; Said, A H; Abernathy, D L; Yan, J
Electron-phonon coupling and thermal transport in the thermoelectric compound Mo3Sb7−xTex Journal Article
In: Physical Review B, vol. 92, no. 21, pp. 214301, 2015.
Links | BibTeX | Tags: electron-phonon coupling, phonon, thermal transport, thermoelectric
@article{bansal_electron-phonon_2015-2,
title = {Electron-phonon coupling and thermal transport in the thermoelectric compound Mo3Sb7−xTex},
author = {D Bansal and Chen W Li and A H Said and D L Abernathy and J Yan},
url = {https://link.aps.org/doi/10.1103/PhysRevB.92.214301},
doi = {10.1103/PhysRevB.92.214301},
year = {2015},
date = {2015-01-01},
journal = {Physical Review B},
volume = {92},
number = {21},
pages = {214301},
keywords = {electron-phonon coupling, phonon, thermal transport, thermoelectric},
pubstate = {published},
tppubtype = {article}
}
Kim, D S; Smith, H L; Niedziela, J L; Li, Chen W; Abernathy, D L; Fultz, B
Phonon anharmonicity in silicon from 100 to 1500 K Journal Article
In: Physical Review B, vol. 91, no. 1, pp. 014307, 2015.
Links | BibTeX | Tags: anharmonicity, lattice, lattice expansion, phonon
@article{Kim:2015fx,
title = {Phonon anharmonicity in silicon from 100 to 1500 K},
author = {D S Kim and H L Smith and J L Niedziela and Chen W Li and D L Abernathy and B Fultz},
url = {https://link.aps.org/doi/10.1103/PhysRevB.91.014307},
doi = {10.1103/PhysRevB.91.014307},
year = {2015},
date = {2015-01-01},
journal = {Physical Review B},
volume = {91},
number = {1},
pages = {014307},
keywords = {anharmonicity, lattice, lattice expansion, phonon},
pubstate = {published},
tppubtype = {article}
}
Budai, J D; Hong, J; Manley, M E; Specht, E D; Li, Chen W; Tischler, J Z; Abernathy, D L; Said, A H; Leu, B M; Boatner, L A; McQueeney, R J; Delaire, O
Metallization of vanadium dioxide driven by large phonon entropy Journal Article
In: Nature, vol. 515, no. 7528, pp. 535-539, 2014.
Links | BibTeX | Tags: anharmonicity, metal-insulator transition, neutron, phonon, synchrotron, thermodynamics, vibrational entropy
@article{budai_metallization_2014,
title = {Metallization of vanadium dioxide driven by large phonon entropy},
author = {J D Budai and J Hong and M E Manley and E D Specht and Chen W Li and J Z Tischler and D L Abernathy and A H Said and B M Leu and L A Boatner and R J McQueeney and O Delaire},
url = {http://www.nature.com/doifinder/10.1038/nature13865},
doi = {10.1038/nature13865},
year = {2014},
date = {2014-11-01},
journal = {Nature},
volume = {515},
number = {7528},
pages = {535-539},
keywords = {anharmonicity, metal-insulator transition, neutron, phonon, synchrotron, thermodynamics, vibrational entropy},
pubstate = {published},
tppubtype = {article}
}
Lan, T; Li, Chen W; Niedziela, J L; Smith, H L; Abernathy, D L; Rossman, G R; Fultz, B
Anharmonic lattice dynamics of Ag2O studied by inelastic neutron scattering and first-principles molecular dynamics simulations Journal Article
In: Physical Review B, vol. 89, no. 5, pp. 2022, 2014.
Links | BibTeX | Tags: anharmonicity, neutron, oxide, phonon
@article{lan_anharmonic_2014,
title = {Anharmonic lattice dynamics of Ag2O studied by inelastic neutron scattering and first-principles molecular dynamics simulations},
author = {T Lan and Chen W Li and J L Niedziela and H L Smith and D L Abernathy and G R Rossman and B Fultz},
url = {https://link.aps.org/doi/10.1103/PhysRevB.89.054306},
doi = {10.1103/PhysRevB.89.054306},
year = {2014},
date = {2014-01-01},
journal = {Physical Review B},
volume = {89},
number = {5},
pages = {2022},
keywords = {anharmonicity, neutron, oxide, phonon},
pubstate = {published},
tppubtype = {article}
}
Li, Chen W; Ma, J; Cao, H B; May, A F; Abernathy, D L; Ehlers, G; Hoffmann, C; Wang, X; Hong, T; Huq, A; Gourdon, O; Delaire, O
Anharmonicity and atomic distribution of SnTe and PbTe thermoelectrics Journal Article
In: Physical Review B, vol. 90, no. 21, pp. 194, 2014.
Links | BibTeX | Tags: anharmonicity, lattice dynamics, neutron, phonon, telluride
@article{li_anharmonicity_2014,
title = {Anharmonicity and atomic distribution of SnTe and PbTe thermoelectrics},
author = {Chen W Li and J Ma and H B Cao and A F May and D L Abernathy and G Ehlers and C Hoffmann and X Wang and T Hong and A Huq and O Gourdon and O Delaire},
url = {https://link.aps.org/doi/10.1103/PhysRevB.90.214303},
doi = {10.1103/PhysRevB.90.214303},
year = {2014},
date = {2014-01-01},
journal = {Physical Review B},
volume = {90},
number = {21},
pages = {194},
keywords = {anharmonicity, lattice dynamics, neutron, phonon, telluride},
pubstate = {published},
tppubtype = {article}
}
Li, Chen W; Hellman, O; Ma, J; May, A F; Cao, H B; Chen, X; Christianson, A D; Ehlers, G; Singh, D J; Sales, B C; Delaire, O
Phonon Self-Energy and Origin of Anomalous Neutron Scattering Spectra in SnTe and PbTe Thermoelectrics Journal Article
In: Physical Review Letters, vol. 112, no. 17, pp. 194, 2014.
Links | BibTeX | Tags: anharmonicity, neutron, phonon, thermoelectric
@article{li_phonon_2014,
title = {Phonon Self-Energy and Origin of Anomalous Neutron Scattering Spectra in SnTe and PbTe Thermoelectrics},
author = {Chen W Li and O Hellman and J Ma and A F May and H B Cao and X Chen and A D Christianson and G Ehlers and D J Singh and B C Sales and O Delaire},
url = {https://link.aps.org/doi/10.1103/PhysRevLett.112.175501},
doi = {10.1103/PhysRevLett.112.175501},
year = {2014},
date = {2014-01-01},
journal = {Physical Review Letters},
volume = {112},
number = {17},
pages = {194},
keywords = {anharmonicity, neutron, phonon, thermoelectric},
pubstate = {published},
tppubtype = {article}
}
Lan, T; Li, Chen W; Fultz, B
In: Physical Review B, vol. 86, no. 13, pp. 134302, 2012.
Abstract | Links | BibTeX | Tags: anharmonicity, first-principles, phonon, Raman
@article{lan_phonon_2012,
title = {Phonon anharmonicity of rutile SnO 2studied by Raman spectrometry and first principles calculations of the kinematics of phonon-phonon interactions},
author = {T Lan and Chen W Li and B Fultz},
url = {https://link.aps.org/doi/10.1103/PhysRevB.86.134302},
doi = {10.1103/PhysRevB.86.134302},
year = {2012},
date = {2012-10-01},
journal = {Physical Review B},
volume = {86},
number = {13},
pages = {134302},
abstract = {Raman spectra of rutile tin dioxide (SnO$_2$) were measured at temperatures from 83 to 873 K. The pure anharmonicity from phonon-phonon interactions was found to be large and comparable to the quasiharmonicity. First-principles calculations of phonon dispersions were used to assess the kinematics of three-phonon and four-phonon processes. These kinematics were used to generate Raman peak widths and shifts, which were fit to measured data to obtain the cubic and quartic components of the anharmonicity for each Raman mode. The $B_2g$ mode had a large quartic component, consistent with the symmetry of its atom displacements. The broadening of the $B_2g$ mode with temperature showed an unusual concave-downwards curvature. This curvature is caused by a change with temperature in the number of down-conversion decay channels, originating with the wide band gap in the phonon dispersions.},
keywords = {anharmonicity, first-principles, phonon, Raman},
pubstate = {published},
tppubtype = {article}
}
Raman spectra of rutile tin dioxide (SnO$_2$) were measured at temperatures from 83 to 873 K. The pure anharmonicity from phonon-phonon interactions was found to be large and comparable to the quasiharmonicity. First-principles calculations of phonon dispersions were used to assess the kinematics of three-phonon and four-phonon processes. These kinematics were used to generate Raman peak widths and shifts, which were fit to measured data to obtain the cubic and quartic components of the anharmonicity for each Raman mode. The $B_2g$ mode had a large quartic component, consistent with the symmetry of its atom displacements. The broadening of the $B_2g$ mode with temperature showed an unusual concave-downwards curvature. This curvature is caused by a change with temperature in the number of down-conversion decay channels, originating with the wide band gap in the phonon dispersions.
Li, Chen W; Tang, X; Munoz, J A; Keith, J B; Tracy, S J; Abernathy, D L; Fultz, B
Structural Relationship between Negative Thermal Expansion and Quartic Anharmonicity of Cubic ScF3 Journal Article
In: Physical Review Letters, vol. 107, no. 19, pp. 195504, 2011.
Links | BibTeX | Tags: anharmonicity. fluoride, lattice expansion, NTE, phonon
@article{li_structural_2011,
title = {Structural Relationship between Negative Thermal Expansion and Quartic Anharmonicity of Cubic ScF3},
author = {Chen W Li and X Tang and J A Munoz and J B Keith and S J Tracy and D L Abernathy and B Fultz},
url = {https://link.aps.org/doi/10.1103/PhysRevLett.107.195504},
doi = {10.1103/PhysRevLett.107.195504},
year = {2011},
date = {2011-01-01},
journal = {Physical Review Letters},
volume = {107},
number = {19},
pages = {195504},
keywords = {anharmonicity. fluoride, lattice expansion, NTE, phonon},
pubstate = {published},
tppubtype = {article}
}
Markovskiy, N D; Munoz, J A; Lucas, M S; Li, Chen W; Delaire, O; Stone, M B; Abernathy, D L; Fultz, B
Nonharmonic phonons in MgB 2at elevated temperatures Journal Article
In: Physical Review B, vol. 83, no. 17, pp. 174301, 2011.
Abstract | Links | BibTeX | Tags: anharmonicity, high temperature, MgB2, phonon
@article{markovskiy_nonharmonic_2011,
title = {Nonharmonic phonons in MgB 2at elevated temperatures},
author = {N D Markovskiy and J A Munoz and M S Lucas and Chen W Li and O Delaire and M B Stone and D L Abernathy and B Fultz},
url = {https://link.aps.org/doi/10.1103/PhysRevB.83.174301},
doi = {10.1103/PhysRevB.83.174301},
year = {2011},
date = {2011-01-01},
journal = {Physical Review B},
volume = {83},
number = {17},
pages = {174301},
abstract = {Inelastic neutron scattering was used to measure phonon spectra in MgB$_2$ and Mg$_0.75$Al$_0.25$B$_2$ from 7 to 750 K to investigate anharmonicity and adiabatic electron-phonon coupling. First-principles calculations of phonons with a linear response method were performed at multiple unit cell volumes, and the Helmholtz free energy was minimized to obtain the lattice parameters and phonon dynamics at elevated temperature in the quasiharmonic approximation. Most of the temperature dependence of the phonon density of states could be understood with the quasiharmonic approximation, although there was also significant thermal broadening of the phonon spectra. In comparison to Mg$_0.75$Al$_0.25$B$_2$, in the energy range of 60 to 80 meV the experimental phonon spectra from MgB$_2$ showed a nonmonotonic change with temperature around 500 K. This may originate from a change with temperature of the adiabatic electron-phonon coupling.},
keywords = {anharmonicity, high temperature, MgB2, phonon},
pubstate = {published},
tppubtype = {article}
}
Inelastic neutron scattering was used to measure phonon spectra in MgB$_2$ and Mg$_0.75$Al$_0.25$B$_2$ from 7 to 750 K to investigate anharmonicity and adiabatic electron-phonon coupling. First-principles calculations of phonons with a linear response method were performed at multiple unit cell volumes, and the Helmholtz free energy was minimized to obtain the lattice parameters and phonon dynamics at elevated temperature in the quasiharmonic approximation. Most of the temperature dependence of the phonon density of states could be understood with the quasiharmonic approximation, although there was also significant thermal broadening of the phonon spectra. In comparison to Mg$_0.75$Al$_0.25$B$_2$, in the energy range of 60 to 80 meV the experimental phonon spectra from MgB$_2$ showed a nonmonotonic change with temperature around 500 K. This may originate from a change with temperature of the adiabatic electron-phonon coupling.
Tang, X; Li, Chen W; Fultz, B
Anharmonicity-induced phonon broadening in aluminum at high temperatures Journal Article
In: Physical Review B, vol. 82, no. 18, pp. 184301, 2010.
Abstract | Links | BibTeX | Tags: Al, anharmonicity, high temperature, lifetime, phonon
@article{tang_anharmonicity-induced_2010,
title = {Anharmonicity-induced phonon broadening in aluminum at high temperatures},
author = {X Tang and Chen W Li and B Fultz},
url = {https://link.aps.org/doi/10.1103/PhysRevB.82.184301},
doi = {10.1103/PhysRevB.82.184301},
year = {2010},
date = {2010-11-01},
journal = {Physical Review B},
volume = {82},
number = {18},
pages = {184301},
abstract = {Thermal phonon broadening in aluminum was studied by theoretical and experimental methods. Using second-order perturbation theory, phonon linewidths from the third-order anharmonicity were calculated from first-principles density-functional theory (DFT) with the supercell finite-displacement method. The importance of all three-phonon processes were assessed and individual phonon broadenings are presented. The good agreement between calculations and prior measurements of phonon linewidths at 300 K and new measurements of the phonon density of states to 750 K indicates that the third-order phonon-phonon interactions calculated from DFT can account for the lifetime broadenings of phonons in aluminum to at least 80% of its melting temperature.},
keywords = {Al, anharmonicity, high temperature, lifetime, phonon},
pubstate = {published},
tppubtype = {article}
}
Thermal phonon broadening in aluminum was studied by theoretical and experimental methods. Using second-order perturbation theory, phonon linewidths from the third-order anharmonicity were calculated from first-principles density-functional theory (DFT) with the supercell finite-displacement method. The importance of all three-phonon processes were assessed and individual phonon broadenings are presented. The good agreement between calculations and prior measurements of phonon linewidths at 300 K and new measurements of the phonon density of states to 750 K indicates that the third-order phonon-phonon interactions calculated from DFT can account for the lifetime broadenings of phonons in aluminum to at least 80% of its melting temperature.
Lucas, M S; Munoz, J A; Mauger, L; Li, Chen W; Sheets, A O; Turgut, Z; Horwath, J; Abernathy, D L; Stone, M B; Delaire, O; Xiao, Y; Fultz, B
Effects of chemical composition and B2 order on phonons in bcc Fe–Co alloys Journal Article
In: Journal of Applied Physics, vol. 108, no. 2, pp. 023519, 2010.
Links | BibTeX | Tags: Fe, phonon, vibrational entropy
@article{lucas_effects_2010,
title = {Effects of chemical composition and B2 order on phonons in bcc Fe\textendashCo alloys},
author = {M S Lucas and J A Munoz and L Mauger and Chen W Li and A O Sheets and Z Turgut and J Horwath and D L Abernathy and M B Stone and O Delaire and Y Xiao and B Fultz},
url = {http://aip.scitation.org/doi/10.1063/1.3456500},
doi = {10.1063/1.3456500},
year = {2010},
date = {2010-01-01},
journal = {Journal of Applied Physics},
volume = {108},
number = {2},
pages = {023519},
keywords = {Fe, phonon, vibrational entropy},
pubstate = {published},
tppubtype = {article}
}
Li, Chen W; McKerns, M M; Fultz, B
A Raman Spectrometry Study of Phonon Anharmonicity of Zirconia at Elevated Temperatures Journal Article
In: Journal of the American Ceramic Society, vol. 94, no. 1, pp. 224-229, 2010.
Abstract | Links | BibTeX | Tags: anharmonicity, high temperature, oxide, phonon, Raman
@article{li_raman_2010,
title = {A Raman Spectrometry Study of Phonon Anharmonicity of Zirconia at Elevated Temperatures},
author = {Chen W Li and M M McKerns and B Fultz},
url = {http://doi.wiley.com/10.1111/j.1551-2916.2010.04057.x},
doi = {10.1111/j.1551-2916.2010.04057.x},
year = {2010},
date = {2010-01-01},
journal = {Journal of the American Ceramic Society},
volume = {94},
number = {1},
pages = {224-229},
abstract = {Raman spectra of monoclinic zirconia (ZrO2) were measured at temperatures of up to 950 K. Temperature‐dependent Raman peak shifts and broadenings were reported and compared with prior results on hafnia...},
keywords = {anharmonicity, high temperature, oxide, phonon, Raman},
pubstate = {published},
tppubtype = {article}
}
Raman spectra of monoclinic zirconia (ZrO2) were measured at temperatures of up to 950 K. Temperature‐dependent Raman peak shifts and broadenings were reported and compared with prior results on hafnia...
Li, Chen W; McKerns, M M; Fultz, B
Raman spectrometry study of phonon anharmonicity of hafnia at elevated temperatures Journal Article
In: Physical Review B, vol. 80, no. 5, pp. 1745, 2009.
Abstract | Links | BibTeX | Tags: anharmonicity, high temperature, oxide, phonon, Raman
@article{li_raman_2009,
title = {Raman spectrometry study of phonon anharmonicity of hafnia at elevated temperatures},
author = {Chen W Li and M M McKerns and B Fultz},
url = {https://link.aps.org/doi/10.1103/PhysRevB.80.054304},
doi = {10.1103/PhysRevB.80.054304},
year = {2009},
date = {2009-08-01},
journal = {Physical Review B},
volume = {80},
number = {5},
pages = {1745},
abstract = {Raman spectra of monoclinic hafnium oxide $(textbackslashtextHfO_2)$ were measured at temperatures up to 1100 K. Raman peak shifts and broadenings are reported. Phonon dynamics calculations were performed with the shell model to obtain the total and partial phonon density of states, and to identify the individual motions of Hf and O atoms in the Raman modes. Correlating these motions to the thermal peak shifts and broadenings, it was found that modes involving changes in oxygen-oxygen bond length were the most anharmonic. The hafnium-dominated modes were more quasiharmonic and showed less broadening with temperature. Comparatively, the oxygen-dominated modes were more influenced by the cubic term in the interatomic potential than the hafnium-dominated modes. An approximately quadratic correlation was found between phonon-line broadening and softening.},
keywords = {anharmonicity, high temperature, oxide, phonon, Raman},
pubstate = {published},
tppubtype = {article}
}
Raman spectra of monoclinic hafnium oxide $(textbackslashtextHfO_2)$ were measured at temperatures up to 1100 K. Raman peak shifts and broadenings are reported. Phonon dynamics calculations were performed with the shell model to obtain the total and partial phonon density of states, and to identify the individual motions of Hf and O atoms in the Raman modes. Correlating these motions to the thermal peak shifts and broadenings, it was found that modes involving changes in oxygen-oxygen bond length were the most anharmonic. The hafnium-dominated modes were more quasiharmonic and showed less broadening with temperature. Comparatively, the oxygen-dominated modes were more influenced by the cubic term in the interatomic potential than the hafnium-dominated modes. An approximately quadratic correlation was found between phonon-line broadening and softening.