On the pressure-dependent phonon characteristics and anomalous thermal expansion coefficient of 3C-SiC

Devki N. Talwar, Indiana University of Pennsylvania


By exploiting a realistic rigid-ion model (RIM) in the quasi-harmonic approximation, we have calculated the pressure- and temperature-dependent phonon characteristics of cubic silicon carbide (3C-SiC). All the RIM parameters at ambient (1 atm or P = 0) and high pressure (P = 22.5 GPa) are carefully optimized by using successive least-square fitting procedures – incorporating critical-point phonon energies as input while the lattice, elastic constants and their pressure derivatives are employed as constraints. For P > 0, we strongly recommend the need of high resolution temperature-dependent second-order Raman scattering measurements to help identify the shifts of optical and acoustical phonons perceived in the two-phonon density of states. Unlike many zinc-blende semiconductors, the present lattice dynamical study of 3C-SiC exhibited no negative thermal expansion (NTE) coefficient α(T) at low temperatures T < 100 K. The mechanism responsible for the absence of NTE behavior is identified and discussed in terms of the bonding and elastic properties of 3C-SiC with comparison to those of diamond (C) and silicon (Si) materials.