Semi-Empirical Force-Field Model for the Ti1−xAlxN  (0 ≤ x ≤ 1) System

Abstract

We present a modified embedded atom method (MEAM) semi-empirical force-field model for the Ti1−xAlxN (0 ≤ x ≤ 1) alloy system. The MEAM parameters, determined via an adaptive simulated-annealing (ASA) minimization scheme, optimize the model’s predictions with respect to 0 K equilibrium volumes, elastic constants, cohesive energies, enthalpies of mixing, and point-defect formation energies, for a set of ≈40 elemental, binary, and ternary Ti-Al-N structures and configurations. Subsequently, the reliability of the model is thoroughly verified against known finite-temperature thermodynamic and kinetic properties of key binary Ti-N and Al-N phases, as well as properties of Ti1−xAlxN (0 < x < 1) alloys. The successful outcome of the validation underscores the transferability of our model, opening the way for large-scale molecular dynamics simulations of, e.g., phase evolution, interfacial processes, and mechanical response in Ti-Al-N-based alloys, superlattices, and nanostructures.

Strength, transformation toughening, and fracture dynamics of rocksalt-structure Ti1−xAlxNSangiovanni1, Tasnádi2, Johnson3 et al. 2020Phys. Rev. Materials

“…It should also be emphasized that our present AIMD simulations pertain the mechanical behavior of (Ti,Al)N solid solutions at 300 K. At this temperature, spinodal decomposition is kinetically blocked, i.e., the temperature is not high enough to activate diffusion of vacancies (vacancy migration in B1 (Ti,Al)N systems requires energies in the range ≈2.5 -4.5 eV [63][64][65][66]). In general, if the operation temperature of (Ti,Al)N coatings remains below ≈1000 Ktypically the onset for decompositionwe find it unlikely that the spinodal decomposition process may occur faster than the strain-mediated lattice transformations seen here.…”

Defects in Titanium Aluminum Nitride-Based Thin Films

“…To be able to accurately model the interatomic forces of materials during CMD simulations, it is important to choose suitable empirical interatomic potentials. Therefore, the modified embedded atom method (MEAM) potential has been parameterized to incorporate the influence of interatomic distances, chemical bond angles, and electronic-screening effects [131,132]. This is especially important for TMN films, which contain a complex combination of ionic, covalent, and metallic bonds.…”

Atomistic Mechanisms Underlying Plasticity and Crack Growth in Ceramics: A Case Study of Aln/Tin Superlattices

“…The classical molecular dynamics (CMD) calculations were run with the LAMMPS code [38] and a Modified Embedded-Atom Method (MEAM) Al-Ti-N potential developed by Almyras et al . [39] . All simulations were performed with a 1 fs time step.…”

“…1 (b) (see dark blue triangle data points at ε = 20%) and can be rationalised based on the energy variations in pure B1 and B3 AlN under strain. Given the order of lattice parameters: a B3 −AlN > a B1 −TiN > a B1 −AlN [39] , an increasing [110]-elongation of AlN(0 01)/TiN(0 01) SL monotonically increases strain energy of the B1 building blocks. At the same time, strain energy of a hypothetical B3-AlN polymorph-which would be in compression-progressively diminishes, and eventually becomes lower than that of the B1-AlN.…”

“…To support and complement AIMD predictions on strainmediated structural transformations and crack growth mechanisms, we carry out "large"-scale CMD simulations employing a semi-empirical potential by Almyras et al . [39] , parameterised and validated for elastic, structural, and thermodynamic properties of binary and pseudobinary Ti-Al-N systems. Although semiempirical potential models generally offer modest accuracy in comparison to ab initio methods, their efficiency allows to overcome limitations of small supercells.…”