Development of a Ni–Al reactive force field for Ni-based superalloy: revealing electrostatic effects on mechanical deformation

Abstract

The physics-informed expression of interatomic potentials is critical to driving accurate molecular dynamics (MD) simulations while most alloy potentials neglect the electrostatic effects explicitly despite the existence of local charge non-neutrality in multi-component alloys. The Ni–Al ReaxFF force field (dubbed ReaxFFNiAl-S22), implementing charge equilibration scheme for explicit electrostatic interactions, was developed in this work for Ni-based superalloy via parametrization based on density functional theory (DFT) calculations. The ReaxFFNiAl-S22 described well the equation of states of Ni and Ni3Al across various polymorphous structures and defects, improving overall accuracy in comparison with several other reported potentials including ReaxFF and Embedded Atom Method (EAM) potentials. Moreover, the short-range repulsion (inner wall) terms implemented in ReaxFFNiAl-S22 extended the capability of describing highly compressed crystal structures. The new potential was applied in the tensile MD simulations of Ni, Al, and Ni/Ni3Al interface models. The obtained strain–stress relationship and the evolution of dislocations are critical to understanding the dynamics of plastic deformation and fracture of alloys. The charge redistribution was particularly examined during the tensile process of Ni3Al, revealing the important role of electrostatic interactions during the mechanical deformation of alloys that are often overlooked before. This work demonstrates that the reactive force field can be used to study the mechanism of mechanical deformation with electrostatic effects. The proposed electrostatic design principle suggests that alloying elements with large electronegativity and strong covalency would benefit electrostatic contribution to the strength of alloys.