Molecular Dynamics of Metals with Many-Atom Interactions

The thermal properties of simple metals, Al and Cu, have been studied using the molecular dynamics simulation method and the effective medium theory (EMT). The results obtained from EMT have a strongly predictive nature, because the model includes many-atom interactions and is based on ab initio-calculations within the framework of the density-functional theory. We have calculated the thermal expansion coefficient of solid and melt phase, melting point and latent heat of fusion for both metals. All the results are in good agreement with the experimental data. The long-range interactions (beyond the nearest neighbours) have been found to be important in the simulations of high-temperature processes (melting, disordered structure) and also in the case of extended crystal defects. The theory gives a good description of the vacancy formation energy and the stacking fault energy. The presence of vacancies lowers the simulated melting point of Al indicating the importance of crystal defects in the melting mechanism. No significant temperature dependence of the vacancy formation energy in Al was observed.