Rare earth elements in α-Ti: A first-principles investigation

The interaction energies between substitutional rare earth (RE) atoms, between RE and interstitial C, N, O, H atoms, as well as between RE and vacancies in α-Ti are calculated via first-principles density-functional theory with projector augmented-wave (PAW) pseudopotentials. The results show that the RE–vacancy and RE–RE interactions are attractive due to the weaker RE–Ti bond than the host Ti–Ti bond. All of the RE atoms investigated in this paper are repulsive to C and N, but attractive to H. RE–O interactions are repulsive for the light RE atoms, though the interactions are very weak for the heavy RE atoms. The mechanism underlying the interactions and their possible influence on the properties of Ti alloys are discussed.