Theory of point defect energetics: A review

Abstract

285-293The energetics of point defects provide the controlling factor in determining the atomistic mechanisms in a wide range of solid state processes. We present here a pedagogical overview of the development of the continuum, quasi-lattice and lattice theories for different classes of point defects and materials. Varied approaches were followed in the past in modelling the relevant perfect crystals for interatomic forces for nonionic solids and model potentials for ionic materials. The earliest continuum approaches are those of Eshelby and Jost for treating point defects as elastic and dielectric singularities. These were followed by semicontinuum Mott-Littleton techniques and the Kanzaki defect force techniques in application to charged and neutral defect species. However the importance of a correct assessment of the dielectric polarization and the anharmonicity of the forces in the evaluation of the enthalpies and volumes have been well documented. Numerical computations of the enthalpies are seen to be sensitive to the choice of potential parameters and polarization models to varying degrees. While the theoretical picture is relatively clear in the case of the simpler materials with a near-ideal pure disorder, materials with mixed type of point defect disorders call for a more challenging simulation of defect environments which among other things should take into account the strong inhomogeneities of defect fields. The paper gives an overview of the evolution covering the highlights of these developments.</span