Molecular dynamics simulations were used to elucidate phonon scattering from the high-energy Σ29 twist grain boundary. In particular, the dependence of energy transmission through the grain boundary on the wavelength and angle of incidence was computed. Transmission through the grain boundary was found to be predominantly a function of the incident phonon frequency. In agreement with previous results, modes with wave vectors perpendicular to the grain-boundary plane exhibit relatively large energy-transmission coefficients. However, as the wavelength decreased and frequency increased, the energy transmission through the interface tends to sharply decrease. To develop a comprehensive picture of elastic phonon scattering, longitudinal-acoustic, transverse-acoustic, and some longitudinal-optical modes were studied. By considering a simple theory that related the energy-transmission coefficients to the Kapitza conductance, it was possible to make a quantitative prediction based upon detailed transmission probabilities. Predictions obtained using this model were relevant for comparison to both the classical (high-temperature) and quantum (low-temperature) regimes.

Scattering of Phonons from a High-Energy Grain Boundary in Silicon - Dependence on Angle of Incidence. C.Kimmer, S.Aubry, A.Skye, P.K.Schelling: Physical Review B, 2007, 75[14], 144105