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Title: Phonon anharmonicity in silicon from 100 to 1500 K

Inelastic neutron scattering was performed on silicon powder to measure the phonon density of states (DOS) from 100 to 1500 K. The mean fractional energy shifts with temperature of the modes were $$\langle$$Δε iiΔT$$\rangle$$=₋0.07, giving a mean isobaric Grüneisen parameter of +6.95±0.67, which is significantly different from the isothermal parameter of +0.98. These large effects are beyond the predictions from quasiharmonic models using density functional theory or experimental data, demonstrating large effects from phonon anharmonicity. At 1500 K the anharmonicity contributes 0.15k B/atom to the vibrational entropy, compared to 0.03k B/atom from quasiharmonicity. Lastly, excellent agreement was found between the entropy from phonon DOS measurements and the reference NIST-JANAF thermodynamic entropy from calorimetric measurements.
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [1]
  1. California Inst. of Technology (CalTech), Pasadena, CA (United States). Dept. of Applied Physics and Materials Science
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Instrument and Source Division
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division
Publication Date:
OSTI Identifier:
Grant/Contract Number:
AC05-00OR22725; FG02-03ER46055
Accepted Manuscript
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 91; Journal Issue: 1; Journal ID: ISSN 1098-0121
American Physical Society (APS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States