Theoretical Approaches to Materials Design: Intergranular Embrittlement

Abstract

One of the ultimate objectives for the electronic structure theory of solids is the first-principles design of materials. Major steps in this direction have already been taken in the form of parameter-free calculations, which are capable of yielding accurate descriptions of a number of structural, electronic, and magnetic properties of metals, semiconductors and even disordered alloys. Furthermore, extensions of these approaches to point defects (substitutional impurities, interstitials, and vacancies) and to interfaces and clean and covered surfaces are showing great promise. However, only recently has there been an attempt to correlate the results of electronic structure calculations with mechanical properties, and only in the past few years have the specific features of electronic structure that could give rise, for example, to brittle versus ductile behavior,^1-5 been addressed. Indeed, despite the complex and manifold origins of mechanical behavior and the relatively poor characterization of the pertinent structures at the atomic level, general trends in certain mechanical properties may be correlated with specific features of electronic structure. An interesting illustration is the control of mechanical properties of semiconductors by electrically-active impurities.⁶ At relatively low temperatures (≲500°C) the dopants have been shown to affect yield stress and hardness through their influence on dislocation velocities,^6-7 the effect being a particularly strong function of dopant concentration in Si and Ge.*