Atomistic theory and computer simulation of grain boundary structure and diffusion

We present a review of the current state of atomistic theory and computer simulation methods in the study of grain boundary structure and diffusion properties. We review the multiplicity of possible local minimum energy structures that arise for the structure of the same grain boundary, particularly in the case of a grain boundary in an ordered alloy. We also review recent structural studies performed for randomly generated grain boundaries. The basic features of the interaction of vacancies with the grain boundary are reviewed for the case of special boundaries. We describe the use of a combination of molecular statics/Monte Carlo techniques for the calculation of diffusion properties along grain boundaries based on many-body interatomic potentials. The method is exemplified in the results obtained for a special grain boundary in the intermetallic compound NiAl. Finally, we describe the studies that have been carried out using molecular dynamics for special grain boundaries in fee metals, showing that both vacancy and interstitial mechanisms may be important. The advantages and disadvantages of these techniques for the study of grain boundary diffusion are discussed.