Atomistic Modelling of All Dislocations and Twins in HCP and BCC Ti

Finite-temperature screw dislocation core structures and dynamics in α-titanium

“…The simulations employ a Deep Potential (DP) trained using DFT results for perfect crystals and defects in the α, β and ω phases of Ti 33 . This DP successfully reproduces the 0 K core structures of the 〈a〉 screw dislocations in Ti as predicted by DFT 33 .…”

“…The three sharp peaks at θ ≃ 75 ∘ , 90 ∘ and 105 ∘ correspond to the π 1 , P and π 2 cores (π 1 and π 2 are both π cores). The peaks for the π cores shift towards θ = 90 ∘ as temperature increases because the c/a ratio increases with temperature 33 . The peak for the π 0 core, if it existed, would be at ~61 ∘ and ~110 ∘ ; however, no peaks exist there, implying that the π 0 core may be ignored.…”

“…where Q 0 iðκÞj is the intrinsic barrier at 0 K, T 0 = 1250 K is the HCP-BCC transition temperature for this DP potential 33 , and we assign q = 3 to give best fit to all the data. Equation ( 13) is proposed based on the observations that (i) the free energy barrier decrease with increasing temperature and (ii) when the HCP phase becomes unstable/metastable, the transition between the core structures is barrierless.…”