Multiple Jumps and Vacancy Diffusion in a Face-Centered-Cubic Metal

Abstract

The diffusion of monovacancies in gold has been studied by computer simulation. Multiple jumps have been found to play a central role in the atomic dynamics at high temperature, and have been shown to be responsible for an upward curvature in the Arrhenius plot of the diffusion coefficient. Appropriate saddle-points on the potential energy surface have been found, supporting the interpretation of vacancy multiple jumps as distinct migration mechanisms.

Atomistic Modeling of Diffusion in Aluminum

“…Contributions to the diffusion coefficient D due to other jump processes like correlated double jumps cannot be excluded at least for the highest simulation temperatures. Therefore, a slight increase of the activation energy obtained from the Arrhenius plot can be expected because migration energies of correlated double jumps are approximately twice the migration energy of single vacancy jumps (Lorenzi and Ercolessi, 1992).…”

“…Of interest are, for example, deviations of DðTÞ from an Arrhenius law as observed for several metals. Such deviations can be investigated by analyzing the contributions of different jump mechanisms (Lorenzi and Ercolessi, 1992). Another interesting aspect is the dynamical reduction of the migration energy for self-diffusion due to low lying phonon modes in bcc metals (Ko¨ehler and Herzig, 1988).…”

Engineering embedded metal nanoparticles with ion beam technology

“…For the high-fluence ion implantation, the initially formed NPs were irradiated by subsequently implanted high-energy self-ions, knocking out atoms from the NPs and left vacancies. For nano-scaled particles in silica, it is easy to reach high-density vacancies under high-fluence of ion irradiation, because the energy barrier for the diffusion of a neutral vacancy in silica is much higher than that in metal [26,27] and they do not easily diffuse into the surrounding amorphous matrix. When the density of vacancies reaches supersaturation, these vacancies aggregate into nanovoids driven by the heat produced by the collision cascades.…”

Self-diffusion in the hexagonal structure of Zirconium and Hafnium: computer simulation studies

“…In doing that, the oscillations (they occur when an atom jumps and immediately returns to the original site) are filtered for the time interval τ ≤ 0.3 ps for α-Zr and τ ≤ 0.4 ps for α-Hf. They are approximately twice the corresponding Debye periods 13 . The oscillations would produce an increase of the jump frequency and no effect on the atomic diffusion.…”

“…Every change in the occupation number implies that a jump has occurred. By recording the involved lattice sites and the occurrence time step, the jumps can be easily classified and the corresponding frequencies evaluated 13,14 . In doing that, the oscillations (they occur when an atom jumps and immediately returns to the original site) are filtered for the time interval τ ≤ 0.3 ps for α-Zr and τ ≤ 0.4 ps for α-Hf.…”