Threshold displacement energy in GaN: Ab initio molecular dynamics study

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Large-scale ab initio molecular dynamics method has been used to determine the threshold displacement energies Ed along five specific directions and to determine the defect configurations created during low energy events. The Ed shows a significant dependence on direction. The minimum Ed is determined to be 39 eV along the ⟨1¯010⟩ direction for a gallium atom and 17.0 eV along the ⟨1¯010⟩ direction for a nitrogen atom, which are in reasonable agreement with the experimental measurements. The average Ed values determined are 73.2 and 32.4 eV for gallium and nitrogen atoms, respectively. The N defects created at low energy events along different crystallographic directions have a similar configuration (a N–N dumbbell configuration), but various configurations for Ga defects are formed in GaN.