Atomistic simulation of titanium. II. Structure of ⅓ 〈1210〉 screw dislocations and slip systems in titanium

Abstract

Abstract The bond-order potential for hcp Ti, constructed in part I, and a central-force Finnis-Sinclair-type potential have been used to study atomistically the core structure of the ⅓ 〈1210〉 screw dislocation. The qualitative features of the core structures are similar in the two cases. The dislocation may either dissociate into Shockley partials on the basal plane or spread in a continuous manner into the prism plane. However, the spreading of the dislocation core into the prism plane is always energetically favoured over the splitting into the basal plane in the case of the bond-order potential whilst the opposite is found in the case of the centralforce Finnis-Sinclair-type potential. Hence, the results obtained using the bond-order potential explain the strong preference for the prism slip over the basal slip in Ti. The most important global parameter is the energy of the intrinsic stacking fault on the basal plane which is so high in the case of the bond-order potential that splitting into Shockley partials is not energetically favourable. The reason for such a high stacking-fault energy is the non-central character of atomic interactions in Ti arising from the significant contribution of d electrons to the bonding, which is correctly captured by the bond-order potential.