Ab-initio simulations of the interactions of isolated defects

Interacting defects give rise to interesting phenomena such as nanovoid and prismatic dislocation loop formation through vacancy coalescence, precipitate nucleation through solute segregation, and solute diffusion through solute-vacancy binding. Though, ab-initio methods such as Density Functional Theory (DFT) is capable of capturing the chemical effects of the defect core, large cell sizes are required to accurately capture the elastic field arising from these defects. Popular DFT codes are cubic scaling with respect to the number of atoms and employ periodic boundary conditions, making accurate simulations of defect interactions difficult. We present an accurate and efficient finite-difference formulation and parallel implementation of Linear Scaling Kohn-Sham Density (Operator) Functional Theory (DFT) for non-periodic systems embedded in a bulk environment. We first discuss the parallel scalability of the framework, and then discuss the interactions of isolated defects in Mg-Al alloys.