Phonon thermal conductivity of a nanowire with amorphous structure

Thermal conductivity of a model nanowire, composed of Zr–Ti–Cu–Ni–Be amorphous alloy, has been studied by computer simulations and theoretical calculations. The results from the molecular dynamics simulations are compared to predictions from Fourier continuum mechanics theory, and with published experimental data. Analysis of the theoretical phonon thermal conductivity follows the previously published incoherent particle model. The novelty of this study is in the employment of amorphous structure, lacking any order or superlattice. The simulated thermal conductivity is significantly lower than that measured by experiments on bulk alloy. It appears that amorphous structure and side-wall scattering reduce thermal diffusivity significantly. Velocity auto correlation time constant increases during heating cycle in proportion to the ratio of atomic weight divided by atomic scattering cross-sectional area.

► MD simulations allow calculations of thermal conductance in amorphous nanowires.
► Velocity autocorrelation of atoms is prolonged when temperature gradient is on.
► Issues on the definition of temperature in non-equilibrium nanoscale systems remain.