Isotope scattering and phonon thermal conductivity in light atom compounds: LiH and LiF
Journal Article
·
· Physical Review B
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Engineered isotope variation is a pathway toward modulating lattice thermal conductivity (κ) of a material through changes in phonon-isotope scattering. The effects of isotope variation on intrinsic thermal resistance is little explored, as varying isotopes have relatively small differences in mass and thus do not affect bulk phonon dispersions. However, for light elements isotope mass variation can be relatively large (e.g., hydrogen and deuterium). Using a first principles Peierls-Boltzmann transport equation approach the effects of isotope variance on lattice thermal transport in ultra-low-mass compound materials LiH and LiF are characterized. The isotope mass variance modifies the intrinsic thermal resistance via modulation of acoustic and optic phonon frequencies, while phonon-isotope scattering from mass disorder plays only a minor role. This leads to some unusual cases where values of isotopically pure systems (6LiH, 7Li2H and 6LiF) are lower than the values from their counterparts with naturally occurring isotopes and phonon-isotope scattering. However, these differences are relatively small. The effects of temperature-driven lattice expansion on phonon dispersions and calculated κ are also discussed. This work provides insight into lattice thermal conductivity modulation with mass variation and the interplay of intrinsic phonon-phonon and phonon-isotope scattering in interesting light atom systems.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE; USDOE Office of Science (SC)
- Grant/Contract Number:
- AC02-05CH11231; AC05-00OR22725
- OSTI ID:
- 1334472
- Alternate ID(s):
- OSTI ID: 1331232
- Journal Information:
- Physical Review B, Journal Name: Physical Review B Journal Issue: 17 Vol. 94; ISSN 2469-9950; ISSN PRBMDO
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Effect of atomic isotopes on phonon modes
|
journal | July 2019 |
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