**Thermal conductivity accumulation in amorphous silica and amorphous
silicon**

JM Larkin and AJH McGaughey, PHYSICAL REVIEW B, 89, 144303 (2014).

DOI: 10.1103/PhysRevB.89.144303

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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