Self-Evolving Atomistic Kinetic Monte Carlo simulations of defects in materials

Active volume is a key concept introduced by the SEAKMC. The following figure illustrates the effects of active volumes on the saddle point searches in the SEAKMC. Without using active volumes, searches with a large system size most likely result in failed searches or unrealistic high barriers. This is because the potential energy increase is much higher in the larger-size systems; the eigenvalue stay positive for many steps during the initial phase of the saddle point searches. [Display omitted] •The framework and current status of SEAKMC is reviewed.•The concept of active volume and its potential development are discussed.•Examples ranging from diffusion to complex defect interactions are presented.•The challenges of on-the-fly KMC methods, especially the SEAKMC, are outlined. The recent development of on-the-fly atomistic kinetic Monte Carlo methods has led to an increased amount attention on the methods and their corresponding capabilities and applications. In this review, the framework and current status of Self-Evolving Atomistic Kinetic Monte Carlo (SEAKMC) are discussed. SEAKMC particularly focuses on defect interaction and evolution with atomistic details without assuming potential defect migration/interaction mechanisms and energies. The strength and limitation of using an active volume, the key concept introduced in SEAKMC, are discussed. Potential criteria for characterizing an active volume are discussed and the influence of active volume size on saddle point energies is illustrated. A procedure starting with a small active volume followed by larger active volumes was found to possess higher efficiency. Applications of SEAKMC, ranging from point defect diffusion, to complex interstitial cluster evolution, to helium interaction with tungsten surfaces, are summarized. A comparison of SEAKMC with molecular dynamics and conventional object kinetic Monte Carlo is demonstrated. Overall, SEAKMC is found to be complimentary to conventional molecular dynamics, especially when the harmonic approximation of transition state theory is accurate. However it is capable of reaching longer time scales than molecular dynamics and it can be used to systematically increase the accuracy of other methods such as object kinetic Monte Carlo. The challenges and potential development directions are also outlined.