Molecular dynamics simulations of substitutional diffusion

Abstract

In atomistic simulations, diffusion energy barriers are usually calculated for each atomic jump path using a nudged elastic band method. Practical materials often involve thousands of distinct atomic jump paths that are not known a priori. Hence, it is often preferred to determine an overall diffusion energy barrier and an overall pre-exponential factor from the Arrhenius equation constructed through molecular dynamics simulations of mean square displacement of the diffusion species at different temperatures. This approach has been well established for interstitial diffusion, but not for substitutional diffusion at the same confidence. Using In 0.1 Ga 0.9 N as an example, we have identified conditions where molecular dynamics simulations can be used to calculate highly converged Arrhenius plots for substitutional alloys. This may enable many complex diffusion problems to be easily and reliably studied in the future using molecular dynamics, provided that moderate computing resources are available. I. INTRODUCTION As the most pervasive rate-limiting mechanism, diffusion impacts almost all the kinetic problems of materials. In the past, theoretical studies of diffusion are usually done through the calculations of the state transition energy barriers for each atomic jump path using molecular statics (MS) simulations in combination with a nudged elastic band method 1,2,3. The problem is that practical materials often involve thousands or more distinct atomic jumps that are not known a priori. It is also unclear as how a large multitude of distinct diffusion energy barriers relate to

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