THERMAL-PROPERTIES OF THE SELF-INTERSTITIAL IN ALUMINUM - AN AB-INITIO MOLECULAR-DYNAMICS STUDY

An order-N ab initio molecular-dynamics method, based on orbital-free density functional theory, is applied to the study of the interstitial in aluminum. The results confirm the (100) dumbbell (in which two ato ms occupy a single lattice site, forming an atom pair in the (100) dir ection) as the lowest-energy structure, with a formation energy simila r to 0.2 eV lower than the classical octahedral interstitial. Formatio n of the interstitial is associated with a reorganization of the atomi c and electronic structure, which extends over several unit cells. The dumbbell interstitial is shown to have a low-energy (similar to 0.084 eV) migration pathway and to be responsible for the appearance of low -frequency resonance modes in the vibrational density of states.