We have revealed, and resolved, an apparent inability of density functional theory, within the local density and generalized gradient approximations, to describe vacancies in Al accurately and consistently. The shortcoming is due to electron correlation effects near electronic edges and we show how to correct for them. We find that the divacancy in Al is energetically unstable and we show that anharmonic atomic vibrations explain the non-Arrhenius temperature dependence of the vacancy concentration.

No abstract

No abstract

We have used density functional theory in an orbital-free, implementation to calculate the properties of pure fcc Al, hcp and bcc Mg, and the meta-stable alloy phase β′′ (Al3Mg). Five linear-response-based kinetic energy density functionals have been used, one of which has a density-dependent (DD) response kernel. We demonstrate that orbital-free density functional theory (OF-DFT) can produce physically accurate properties for Al–Mg alloys, if the kinetic energy density functional employed has a DD-kernel.

No abstract

No abstract

The early stages of clustering in Al-14.8 Mg alloy have been studied using atomistic modelling and 3DAP analysis. Atomistic modelling was based on first-principles quantum mechanical calculations and Monte Carlo (MC) based techniques. A good agreement between the experimental results and simulated data was obtained showing the appropriateness of the theoretical approach used. It has been shown that after 720 h at 35°C (308 K) clustering of Mg was clearly detectable in the experimental alloy. The simulated data after 200 MC steps corresponded well to the experimental results obtained after ageing for 720 h.