Molecular dynamics simulations on heat conduction in nano-porous Si

We investigate heat conduction of silicon nano-porous structures by molecular-dynamics simulations (MDs). We calculated the phonon dispersion curves of the nano-structured Si to understand the effects of nano-structures on phonon properties, such as phonon group velocity and phonon density of states. The dispersion curves were calculated from MDs results by using the 2D time-space Fourier transformation. Frequency gaps in phonon dispersion curves reduce the phonon group velocity in the periodic nano-porous structures. Moreover the group velocity of phonon is reduced due to new phonon modes even though the nano-porous was random. The results show that nanoporous structures reduce the thermal conductivity as well as superlattices.