First-Principles Calculations of Structural, Lattice Dynamical, and Thermodynamic Properties of 4H-SiC

This study systematically investigates the structural, lattice dynamical, and thermodynamic properties of 4H-SiC using density functional theory (DFT), density functional perturbation theory (DFPT), and Boltzmann transport equation (BTE) frameworks. Using DFPT, we obtain the phonon frequencies and the phonon dispersion curves, as well as corresponding density of states. Quasi-harmonic approach was employed to analyze the thermodynamic parameters of 4H-SiC. The results reveal that the dynamically stable phonon spectrum provides a foundation for probing thermal transport mechanisms at high temperatures. BTE calculations demonstrate that the temperature-dependent lattice thermal conductivity originates from enhanced Umklapp scattering, with the nonlinear increase in the Grüneisen parameter quantitatively validated through relaxationtime approximations. The exceptional thermal stability is associated with its high thermal conductivity and the saturating behavior of the Grüneisen parameter at high temperatures, w hich suggests a suppression of strong anharmonic scattering. Correspondingly, the saturation of the thermal expansion coefficient at high temperatures is attributed to the weakened volume dependence of phonon frequencies. This work establishes an integrated first-principles workflow that provides a comprehensive self-consistent dataset across structural, lattice dynamical, and thermodynamic properties, offering theoretical guidance for optimizing 4H-SiC performance in extreme-environment applications.