Quantifying the Effect of Point and Line Defect Densities on the melting Temperature in the Transition Metals
Molecular dynamics simulations of the melting process of bulk copper and gold were performed using Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). The aim of the study was to understand the effects of high pressures and defects on the melting temperature. The simulations were visualised using Visual Molecular Dynamics (VMD). The melting temperature of the perfect crystals were found to be higher than the experimentally observed values. The melting temperature as a function of pressure was determined and found to be in good agreement with experimental results. Vacancies and line defects in the form of dislocations were then introduced into the simulation cell and the melting temperatures recalculated. In both scenarios, we find that the melting temperature decreases as the defect density is increased bringing it closer to the experimentally observed value. Based on the pressure dependence of the melting curve, we conclude that vacancies are not the driving force for the melting transition.
Some of the MD simulations were carried out on the ARCCA computing facilities at Cardiff University. CCM wishes to thank Professor Norman March for the many fruitful discussions on the topic of melting.
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