Vibrational mean free paths and thermal conductivity of amorphous silicon from non-equilibrium molecular dynamics simulations

The frequency-dependent mean free paths (MFPs) of vibrational heat carriers in amorphous silicon are predicted from the length dependence of the spectrally decomposed heat current (SDHC) obtained from non-equilibrium molecular dynamics simulations. The results suggest a (frequency)−2 scaling of the room-temperature MFPs below 5 THz. The MFPs exhibit a local maximum at a frequency of 8 THz and fall below 1 nm at frequencies greater than 10 THz, indicating localized vibrations. The MFPs extracted from sub-10 nm system-size simulations are used to predict the length-dependence of thermal conductivity up to system sizes of 100 nm and good agreement is found with independent molecular dynamics simulations. Weighting the SDHC by the frequency-dependent quantum occupation function provides a simple and convenient method to account for quantum statistics and provides reasonable agreement with the experimentally-measured trend and magnitude.

DOI

10.1063/1.4968617

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Sääskilahti, K, Oksanen, J, Tulkki, J, McGaughey, A J H & Volz, S 2016, 'Vibrational mean free paths and thermal conductivity of amorphous silicon from non-equilibrium molecular dynamics simulations', AIP Advances, vol. 6, no. 12, 121904. https://doi.org/10.1063/1.4968617

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https://urn.fi/URN:NBN:fi:aalto-201705114313

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[article-cris] Perustieteiden korkeakoulu / SCI

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Vibrational mean free paths and thermal conductivity of amorphous silicon from non-equilibrium molecular dynamics simulations

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