First-principles Calculation on Screw Dislocation Core Properties in BCC Molybdenum

Predicting atomistic properties of a dislocation is a first step toward an understanding of plastic behavior of materials, in particular BCC metals. The core structure and Peierls stress of a screw dislocation in BCC metals have been studied over the years using the first-principles and empirical methods, however, their conclusions vary due to the inefficiency of the methods. We have executed first-principles calculations based on the density functional method, employing the most accurate 1 × 1 × 20 k-point samplings, to determine the core structure and Peierls stress of the a0/2[111] screw dislocation of molybdenum. We have concluded that the core has a 6-fold structure, and determined the Peierls stress of 1.8 GPa for the simple shear strain along the (–110)<111> direction.