A COMPUTER-SIMULATION STUDY OF INTERSTITIAL-TWIN BOUNDARY INTERACTIONS IN HCP METALS

The formation of stable interstitial configurations in the {11 (2) ove r bar 1}, {11 (2) over bar 2}, {10 (1) over bar 1} and {10 (1) over ba r 2} twin boundaries in hexagonal closed packed metals has been studie d by computer simulation. The crystals have been modelled by either a pair potential for a crystal with a near-ideal c/a lattice parameter r atio or a many-body potential for titanium. These potentials have prov ed to be satisfactory for the simulation of both twin boundaries and p oint defects. It is found that the twin boundary gives rise to stable interstitial configurations exhibiting a high binding energy. These co nfigurations are not found in the perfect lattice and are highly depen dent on the twin crystallography. The variation of the twin-interstiti al binding energy as a function of the defect distance to the interfac e depends also on the twin structure. The features are qualitatively t he same for both potentials for the {11 (2) over bar 1} and {11 (2) ov er bar 2} twins, but differences between the two model potentials are observed for the {10 (1) over bar 1} and {10 (1) over bar 2} twin boun daries.