Development of an interatomic potential for the simulation of defects, plasticity, and phase transformations in titanium

Abstract

New interatomic potentials describing defects, plasticity, and high temperature phase transitions for Ti are presented. Fitting the martensitic hcp-bcc phase transformation temperature requires an efficient and accurate method to determine it. We apply a molecular dynamics method based on determination of the melting temperature of competing solid phases, and Gibbs-Helmholtz integration, and a lattice-switch Monte Carlo method: these agree on the hcp-bcc transformation temperatures to within 2 K. We were able to develop embedded atom potentials which give a good fit to either low or high temperature data, but not both. The first developed potential (Ti1) reproduces the hcp-bcc transformation and melting temperatures and is suitable for the simulation of phase transitions and bcc Ti. Two other potentials (Ti2 and Ti3) correctly describe defect properties and can be used to simulate plasticity or radiation damage in hcp Ti. The fact that a single embedded atom method potential cannot describe both low and high temperature phases may be attributed to neglect of electronic degrees of freedom, notably bcc has a much higher electronic entropy. A temperature-dependent potential obtained from the combination of potentials Ti1 and Ti2 may be used to simulate Ti properties at any temperature.

The α → ω Transformation in Titanium-Cobalt Alloys under High-Pressure Torsion

“…The formation of ω-phase in Ti, Zr, and Hf, and their alloys have attracted much theoretical work and computer simulations [3,7,10,[55][56][57][58][59][60][61][62][63][64][65][66][67][68]. Already in 2001, Greef et al performed the first-principles electronic structure calculations and constructed the equilibrium free energies for the α-and ω-phases in Ti [55].…”

“…The crystallographic mechanism of the α ↔ ω (or α ↔ β ↔ ω) phase transformation was described in Reference [3] as being based on two possible orientation relationships: OR 1 (0001) α (0111) ω ; 1120 α 1101 ω and OR 2 (0001) α (1120) ω ; 1120 α 0001 ω . However, the using of different pseudopotentials to represent titanium (such as those of Ackland, Mishin, Kim or Hennig) can lead to the significant differences in the calculation results [56][57][58]. Thus, the apparently arbitrary choices in the reference configuration can lead to significant differences in the calculated quantities [56].…”

Stacking faults and the -surface on first-order pyramidal planes in -titanium

“…This discrepancy has been discussed in previous publications [19,29]. In recent work it has been shown that this potential fitting procedure can be improved by including basal faults in the set of fitting parameters with the inclusion longer ranged interactions [30].…”

Conceptual and practical bases for the high accuracy of machine learning interatomic potentials: Application to elemental titanium

“…Secondly, we develop the most accurate MLIP of the elemental Ti ever reported using a linearized MLIP framework. As shown later, the high accuracy of [10][11][12][13] and MEAM [14][15][16][17] potentials. Some of these curves are obtained from the interatomic potential repository project [18] and KIM project [19].…”