An order-N first-principles molecular dynamics method, which was based upon orbital-free density functional theory, was applied to the study of interstitials. The results confirmed that the <100> dumb-bell (in which 2 atoms occupied a single lattice site to form an atom pair in the <100> direction) was the lowest-energy structure; with a formation energy that was about 0.2eV lower than that of the classical octahedral interstitial. The formation of the interstitial was associated with a reorganization, of the atomic and electronic structures, which extended over several unit cells. The dumb-bell interstitial was shown to have a low-energy (0.084eV) migration pathway, and to be responsible for the appearance of low-frequency resonance modes in the vibrational density of states.

Thermal Properties of the Self-Interstitial in Aluminum: an ab initio Molecular-Dynamics Study. B.J.Jesson, M.Foley, P.A.Madden: Physical Review B, 1997, 55[8], 4941-6