**About this Abstract** |

**Meeting** |
**2021 TMS Annual Meeting & Exhibition
** |

**Symposium
** |
**Thermal Property Characterization, Modeling, and Theory in Extreme Environments
** |

**Presentation Title** |
Ultra-high lattice thermal conductivity and the
effect of pressure in superhard hexagonal BC2N |

**Author(s)** |
Safoura Nayeb Sadeghi, S. Mehdi Vaez Allaei, Mona Zebarjadi, Keivan Esfarjani |

**On-Site Speaker (Planned)** |
Keivan Esfarjani |

**Abstract Scope** |
Hexagonal BC2N is a superhard material recently identified to be comparable to or even harder than cubic boron nitride (c-BN). Using a first-principles approach to calculate force constants and an exact numerical solution to the phonon Boltzmann equation, we show that BC2N has a high lattice thermal conductivity exceeding that of c-BN owing to the strong C–C and B–N bonds, which produce high group velocities. Its coefficient of thermal expansion (CTE) is found to match that of Si above 400 K The combination of large thermal conductivity and a good CTE match with
that of Si, makes BC2N a promising material for use in thermal management and high-power electronics applications. We show that the application of compressive strain increases the thermal conductivity significantly.
This enhancement results from the overall increased frequency scale with pressure, which makes acoustic and optic velocities higher, and weaker phonon–phonon scattering rates. |

**Proceedings Inclusion?** |
Planned: |