Atomistic Modeling of Diffusion in Aluminum

Abstract

We present molecular-dynamics simulations of self-diffusion in Al. In order to facilitate the description of elastic and vibrational properties as well as vacancy migration, an embedded-atom method potential was used in the simulations. This potential was specifically designed to reproduce the T ¼ 0 K equation of state of Al obtained by ab initio total-energy calculations. We show that the temperature dependent self-diffusion coefficient obeys an Arrhenius law and that the resulting dynamical migration energy is slightly larger than the static migration energy obtained by using classical rate theory.

Molecular-dynamics study of mechanical deformation in nano-crystalline aluminum

“…One explanation is connected to the effective pair potential of the Al interaction used here. [13] The effective pair potential has a double-minima structure that agrees with pseudopotential calculations by Hafner [23] and with other descriptions of Al. As can be seen from the construction of this EAM Al potential, [13] the double-minima structure comes from the relatively low C 44 elastic constant of Al.…”

“…The atomic interactions were described by an embedded-atom method(EAM) potential [12] especially designed to model Al. [13] For the grain sizes investigated (d Ͻ 10 nm), we find an inverse Hall-Petch relation. The deformation processes here are dominated by grain rotation, sliding, and growth-mechanisms that result from the large fraction of grain boundary atoms as seen previously for other face-centered cubic metals.…”

Molecular-dynamics study of the local symmetry changes in metallic liquids

“…This additional fit to ab initio data leads to a potential which is softer at lower inter-particle distances than the corresponding interaction potential which is solely based on the experimental data describing the thermal equilibrium state of the metal. In particular this interaction allows the investigation of diffusion processes via vacancies in solid aluminum, yielding a temperature dependence for diffusion coefficient which is in reasonable agreement with experiment (Grabowski et al, 2002). Therefore, this EAM potential is best suited for investigating the local symmetry changes in the undercooled liquid metal regime.…”

“…In addition, in the choice of potential parameters the equation of state, E(V ), obtained from ab initio calculations has been taken into account. Details of the fit procedure for the case of Al can be found in (Grabowski et al, 2002). This additional fit to ab initio data leads to a potential which is softer at lower inter-particle distances than the corresponding interaction potential which is solely based on the experimental data describing the thermal equilibrium state of the metal.…”

“…In this paper we concentrate on details of the temperature dependence of the local symmetries (atomic short-range order) in stable undercooled monoatomic metallic melts like Al on the basis of molecular-dynamics simulations using an optimized EAM potential for Al (Grabowski et al, 2002). Our aim is to check, on the basis of the simulations, whether the increase of icosahedral short-range order with decreasing temperature, as observed in the experiment for bulk Fe, Co, Ni and Zr liquids , holds also for Al.…”