Point defects in bcc crystals: Structures, transition kinetics, and melting implications

Abstract

Structures corresponding to various potential energy minima have been examined for a classical model whose pair interactions produce a body‐centered‐cubic crystalline ground state. The method used is molecular dynamics computer simulation for 128 particles with frequent steepest‐descent mapping onto nearby minima. The elementary structural excitation out of the crystalline absolute minimum is creation of a vacancy, split‐interstitial defect pair. This excitation process upon repetition shows a defect softening of the medium. Transition states (saddle points) have been located for some pairs of neighboring minima, and vibrational modes have been calculated for minima and for transition states. A simple melting theory based on these observations is proposed which satisfactorily describes the model’s first‐order melting behavior.