Abstract
Although molecular dynamics simulations of energetic impacts and collision cascades in graphite have been investigated for over 25years, recent investigations have shown a difference between the types of defects predicted by the commonly used empirical potentials compared to ab initio calculations. As a result a new ReaXFF potential has been fitted which reproduces the formation energies of many of the defects predicted by the ab initio calculations and the energy pathways between different defect states, important for investigating long term defect evolution. The data sets in the fitting have been added to the existing data sets used for modelling hydrocarbons and fullerenes. The elastic properties of the potential are less well modelled than the point defect structures with the elastic constants c33 being too high and c44 too low compared to experiment. Preliminary results of low energy collision cascades show many point defect structures develop that are in agreement with those predicted from the ab initio results.
Highlights
The advent of three-body and bond order potentials of the Tersoff form in the late 1980s [1,2] meant that large scale molecular dynamics computer simulations could be carried out on covalent materials for the first time
Later more sophisticated potentials such as AIREBO and EDIP were developed [6,7] to overcome some of these deficiencies, and such potentials have been recently used to investigate collision cascades in perfect and polycrystalline graphite [8,9]
This paper reports on a new ReaxFF model which fits the energies of small defect structures in graphite more exactly to the DFT with the local density approximation (LDA) results
Summary
Molecular dynamics simulations of energetic impacts and collision cascades in graphite have been investigated for over 25 years, recent investigations have shown a difference between the types of defects predicted by the commonly used empirical potentials compared to ab initio calculations. As a result a new ReaXFF potential has been fitted which reproduces the formation energies of many of the defects predicted by the ab initio calculations and the energy pathways between different defect states, important for investigating long term defect evolution. The elastic properties of the potential are less well modelled than the point defect structures with the elastic constants c33 being too high and c44 too low compared to experiment. Preliminary results of low energy collision cascades show many point defect structures develop that are in agreement with those predicted from the ab initio results.
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