A comparative study of molecular dynamics simulation methods for evaluation of the thermal conductivity and phonon transport in Si nanowires

Abstract

In the present study, various MD methods including Equilibrium Molecular Dynamics (EMD) and two different Non- Equilibrium Molecular Dynamics (NEMD) methods are studied and compared for evaluation of the thermal conductivity and total and partial phonon density of states spectra in silicon nanowires, as a case study. The thermal conductivity of nanowires was determined as a function of length, cross section width and temperature. According to the results obtained via various MD methods, the thermal conductivity increases by increasing the length and cross section or decreasing the MD temperature. However, it was observed that despite the same initial conditions, different MD methods could predict considerably different values for the thermal conductivity which was found to be due to the different equilibrium temperature achieved in different methods. The total phonon density of states spectra was then employed to analyze the phonon transport properties of a 45 nm SiNW simulated using various MD techniques. Two major peaks were observed at around 16.5 and 5 THz which are attributed to Si-Si bond modes. Finally partial phonon density of states was calculated to differentiate the contributions to the phonon DOS from surface atoms compared to central atoms.