Phonon Thermal Conductivity Of F.C.C. Cu By Molecular Dynamics Simulation

Phonon dynamics and phonon thermal conductivity of f.c.c. Cu are investigated in detail in the temperature range 200 - 1300 K within the framework of equilibrium molecular dynamics simulations making use of the Green-Kubo formalism and one of the most reliable embedded-atom method potentials. It is found that the temporal decay of the heat current autocorrelation function of the f.c.c. Cu model at low and intermediate temperatures demonstrates a more complex behaviour than the two-stage decay observed previously for the f.c.c. Ar model. After the first stage of decay, it demonstrates a peak in the temperature range 200 - 800 K. The intensity of the peak decreases as the temperature increases. At 900 K, it transforms to a shoulder which diminishes almost entirely at 1200 K. It is suggested that the peak may be activated by the influence of the Cauchy pressure in f.c.c. Cu on the phonon dynamics. A decomposition model of the heat current autocorrelation function of a monatomic f.c.c. lattice is introduced. This model can capture all contributions to the function discussed in the literature. It is found that the temperature dependence of the phonon thermal conductivity of the f.c.c. Cu model is in good agreement with previous calculations on the f.c.c. Ar model which follows an exponent close to -1.4, i.e. varies more rapidly than the T-1 law predicted by the theory. The calculated phonon thermal conductivity of the f.c.c. Cu is found to be about one order of magnitude higher than the f.c.c. Ar. This is explained by the inclusion of the electronic contribution to the bulk lattice properties during the fitting of the embedded-atom method potential functions to the experimental or ab initio data. It is demonstrated that the electronic contribution to the total thermal conductivity of f.c.c. Cu dominates over the whole studied temperature range. Nevertheless, the phonon contribution increases as the temperature decreases. The contribution can be estimated to be about 0.5 % at 1300 K and about 5 % at 200 K. © (2013) Trans Tech Publications, Switzerland