Thermal conductivity of amorphous SiO2 by first-principles molecular dynamics

Abstract

The approach-to-equilibrium molecular dynamics (AEMD) methodology implemented within a first-principles molecular dynamics (FPMD) scheme is applied to amorphous SiO2. In this disordered material, measurements of the thermal conductivity indicate no reduction down to 10 nm. In view of these premises, we calculate the thermal conductivity of amorphous SiO2 in the size range comprised between 2 and 8 nm via the AEMD/FPMD approach. The thermal conductivity agrees with experiments for the largest sizes we considered, while it is strongly reduced for values not accessible to experimental resolution (up to 50% for 2 nm). This behavior is close to that found in amorphous chalcogenides GeTe4 and Ge2Sb2Te5 within the same AEMD/FPMD approach. Taken together, these results show that the observed decrease of the thermal conductivity is a general feature of disordered networks and in any case cannot be taken as peculiar to a specific class of systems.