Nosé-Hoover molecular-dynamics study of self-pipe-diffusion in gold using many-atom interactions

Self-diffusion along the [112] Shockley parital dislocation pair (self-pipe-diffusion) in Au is studied with Nosé-Hoover molecular dynamics (MD) using the many-atom Ackland-Tichy-Vitek-Finnis model. We find the following formation energy difference between interstitials (i) and vacancies (v) at partial dislocations: ΔEf=Ef(i)-Ef(v)=1.3 eV. Thermal disorder in the stacking fault region makes it difficult (or even impossible) to follow the migration of single vacancies or interstitials sufficiently long times in the temperature range 0.78Tm. . . Tm (Tm=1475 K is the melting temperature). The diffusion induced by one vacancy and one interstitial calculated at the temperature range 1150–1400 K gives the following migration energies: Em(v)=0.75 eV and Em(i)≊0.0 eV. Since the activation energy for interstitials is about 0.5 eV larger than that for vacancies, self-pipe-diffusion is more vacancy type than interstitial type. The components of the induced diffusion constants indicate the spread of diffusion into the whole stacking fault region.