**About this Abstract** |

**Meeting** |
**2017 TMS Annual Meeting & Exhibition
** |

**Symposium
** |
**Computational Thermodynamics and Kinetics
** |

**Presentation Title** |
Phonon Thermodynamics of Silicon |

**Author(s)** |
Dennis Sungtae Kim, Olle Hellman, Hillary Smith, Jiao Lin, Jane Herriman, Jennifer Niedziela, Douglas Abernathy, Brent Fultz |

**On-Site Speaker (Planned)** |
Dennis Sungtae Kim |

**Abstract Scope** |
Phonons are the main source of total entropy, thermal expansion, and thermal transport properties of most materials, so it is essential to know the temperature-dependent lattice dynamics. We measured phonon dispersions in silicon by neutron inelastic scattering at elevated temperatures. Although the quasiharmonic model (harmonic phonons renormalized by volume) predicts the experimental entropy and thermal expansion of silicon fairly well, it does not predict correctly the temperature-dependent lattice dynamics. The necessity to include anharmonicities to describe the lattice dynamics throughout the temperature range was verified by ab-initio calculations using the temperature-dependent effective potential method. Large phonon anharmonicities manifested through shifts and broadenings go beyond the quasiharmonic model even at low temperatures. The quasiharmonic model correctly predicts the macroscopic values due to a cancelation of phonon shifts, but its validity should not be assumed because it predicts average quantities. |

**Proceedings Inclusion?** |
Planned: Supplemental Proceedings volume |