Comment on “Development of an interatomic potential for the simulation of defects, plasticity, and phase transformations in titanium” [J. Chem. Phys. 145, 154102 (2016)]

Recently Mendelev, Underwood, and Ackland1 (MUA) published three interatomic potentials (IPs) Ti1, Ti2, and Ti3 for pure Ti. These IPs were developed to model atomistically defects, plasticity, and phase changes in Ti. In this comment we compare quantitatively the γsurfaces predicted by these IPs on the basal and {11̄01} first order pyramidal or pyramidal I planes of hexagonal close-packed Ti with those we computed recently by density functional theory (DFT)2. We also compare with the γ-surfaces computed with the IP developed by Ackland3, which we call Ti0. Local minima in the γ-surface4 correspond to stable stacking faults, which indicate the possibility, depending on the energy of the local minimum, of dissociation of lattice dislocations into partial dislocations separated by the stacking fault. In addition, the slope of the γ-surface determines the force per unit area tending to constrict the core of dislocations in the slip plane5. The accuracy of a γ-surface is therefore of some importance for modelling plasticity on that slip plane.