Thermal conductivity accumulation in amorphous silica and amorphous silicon
JM Larkin and AJH McGaughey, PHYSICAL REVIEW B, 89, 144303 (2014).
We predict the properties of the propagating and nonpropagating vibrational modes in amorphous silica (a-SiO2) and amorphous silicon (a-Si) and, from them, thermal conductivity accumulation functions. The calculations are performed using molecular dynamics simulations, lattice dynamics calculations, and theoretical models. For a-SiO2, the propagating modes contribute negligibly to thermal conductivity (6%), in agreement with the thermal conductivity accumulation measured by Regner et al. Nat. Commun. 4, 1640 ( 2013). For a-Si, propagating modes with mean-free paths up to 1 mu m contribute 40% of the total thermal conductivity. The predicted contribution to thermal conductivity from nonpropagating modes and the total thermal conductivity for a-Si are in agreement with the measurements of Regner et al. The accumulation in the measurements, however, takes place over a narrower band of mean-free paths (100 nm-1 mu m) than that predicted (10 nm-1 mu m).
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