  In this work we present a molecular dynamics investigation of thermal
transport in a silica-gallium nitride nanocomposite. A surprising enhancement
of the thermal conductivity for crystalline volume fractions larger than 5% is
found, which cannot be predicted by an effective medium approach, not even
including percolation effects, the model systematically leading to an
underestimation of the effective thermal conductivity. The behavior can instead
be reproduced if an effective volume fraction twice larger than the real one is
assumed, which translates in a percolation effect surprisingly stronger than
the usual one. Such scenario can be understood in terms of a phonon tunneling
between inclusions, enhanced by the iso-orientation of all particles. Indeed,
if a misorientation is introduced, the thermal conductivity strongly decreases.
We also show that a percolating nanocomposite clearly stand in a different
position than other nanocomopsites, where thermal transport is domimnated by
the interface scattering, and where parameters such as the interface density
play a major role, differently from our case.
