Atomistic simulation of the energy barrier for dislocation movement in Si

Abstract

We examine the mobility of an edge dislocation pair on the shuffle plane in Si using action-derived molecular dynamics (ADMD). ADMD is one of the specially designed schemes for finding out the reaction pathways passing through transition states in the landscape of potential energy surfaces. Via ADMD calculations, the various structural changes of dislocation line with atomic resolution and their corresponding energy barriers are evaluated during the dislocation motion. The energy barrier for the movement of an edge dislocation pair on shuffle plane is about 0.24 eV. In this case, one bond between the atoms at the dislocation line is broken first, and then a new bond is formed with the neighboring atom. The movement of the dislocation line is achieved by a sequence of making new bond after bond-breaking of concerned atoms, which occur layer by layer. When the dislocation moves through this mechanism, energy barrier for the dislocation movement does not depend on the length of dislocation line. Thus the present result enables one to surmount the inherent limitation of Peierls-Nabarro's two-dimensional continuum model, which may fail to describe successfully dislocation motion on the atomistic level.