Investigation on interfacial thermal resistance and phonon scattering at twist boundary of silicon

Grain interfaces in nanocrystalline materials play a critical role in thermal transport. A series of twist boundary thermal resistances in silicon is investigated by the nonequilibrium molecular dynamics simulation so as to find the relationship between the boundary resistance, the twist angle, the boundary energy and temperature. The results indicate that the magnitude of the twist grain boundary (GB) thermal resistance is on the order of 10⁻⁹ m² KW⁻¹, and the GB thermal resistance becomes larger with increasing GB energy at most twist angles, and it drops obviously with increasing temperature. The phonon wave packet dynamic simulation shows that the transmission coefficient of the low frequency phonons with long wavelength is close to 100% at the boundary with different twist angles. The transmission coefficient of the longitudinal phonon wave packet decreases with increasing frequency and transverse phonons are produced due to the scattering. In most cases, higher grain boundary energy corresponds to lower transmission coefficient, leading to larger GB thermal resistance.