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“Phonons”

“Phonons”. Vibrational normal modes Evolution from molecule to solid Heat conduction What are vibrations like in glasses?. P. B. Allen, visiting Applied Physics at Columbia On leave from SUNY Stony Brook. Euken Einstein Debye Born Peierls Frenkel Brockhouse. PBA and J. Kelner

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“Phonons”

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  1. “Phonons” Vibrational normal modes Evolution from molecule to solid Heat conduction What are vibrations like in glasses? P. B. Allen, visiting Applied Physics at Columbia On leave from SUNY Stony Brook

  2. Euken Einstein Debye Born Peierls Frenkel Brockhouse

  3. PBA and J. Kelner Am. J. Phys. 66, 497 (1998) group velocity phase velocity

  4. Energy transport, weakly disordered 1d chain 0.93 < K < 1.07 uniform random deviations

  5. Ballistic motion of wavepacket for 0 < t < 100 Center of energy stops systematic motion by t=200 Non-Chaotic Evolution

  6. Diffusive motion, 100 < t < 1000 Localization, t > 2000 (no further energy transport)

  7. Phonon dispersion in tungsten metal “first principles” calculation Density-functional theory C. Bungaro, thesis, SISSA, 1995 (with Baroni and Gironcoli)

  8. Heat Conduction by Phonons Experiments: Euken Theories: Einstein, Debye R. Peierls, thesis, Zurich, 1929 4000 W/mK “Phonon gas model”

  9. Thesis supervised by Arne Claesson KCl

  10. 3000 W/mK 1 W/mK “plateau”

  11. “Phase diagram of silicon by molecular dynamics” J. Q. Broughton and X. P. Li Phys. Rev. B 35, 9120-9127 (1987) interatomic forces

  12. vibrational density of states amorphous silicon PBA, J. L. Feldman, J. Fabian Neutron Scattering data atomcoordinates crystal vs. amorphous

  13. Phonon gas model: does not apply! Group velocity vi is undefined! Lattice analog of Kubo-Greenwood formula (Allen and Feldman, 1987)

  14. “Anharmonic Decay of Vibrational States in Amorphous Silicon” Jaroslav Fabian and Philip B. Allen Phys. Rev. Lett. 77, 3839 (1996)

  15. Observation of Giant Kohn Anomaly in the One-Dimensional Conductor K2Pt(CN)4Br0.3· 3H2O B. Renker, H. Rietschel, L. Pintschovius, W. Gläser, P. Brüesch, D. Kuse, and M. J. Rice Phys. Rev. Lett. 30, 1144 (1973) Peierls-Overhauser Insulator, or “band Jahn-Teller system” partly-filled electron energy band “Peierls gap” 2D

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