Simulations of crack initiation in silicon M. M aki-Jaskari * , K. Kaski, A. Kuronen Laboratory of Computational Engineering, Helsinki University of Technology, P.O. Box 9400, 02015 Hut, Finland Abstract The applicability of semiempirical potential energy models for describing crack initiation in covalently bonded silicon has been studied using classical molecular dynamics (MD) approach. For describing interatomic interactions, in this approach we use the recently developed environment dependent interatomic potential (EDIP) with two- and three-body terms. Since the original form of this potential was found problematic in describing bond-breaking properties we tested three dierent modi®cations of it. An additional point of interest in this study were crack tip structures observed preceding the actual fracture. Our results, with an idealized simulation setup, indicated formation of stable ring-like structures. Unless angular forces were made relatively strong, these ring-like structures were formed near the crack tip before and even during the crack initiation. These relatively stable structures could cause crack initiation to stop temporarily, especially at early stages of fracture. Ó 2000 Elsevier Science B.V. All rights reserved. Keywords: Silicon structures; Brittle fracture; Molecular Dynamics simulations 1. Introduction One of the basic issues in analysing the strength and fracture properties of materials is the dy- namics of crack growth originating from a single ¯aw on a surface of the sample. The nature of this phenomenon has consequences to material failure. Among brittle materials silicon is an interesting example due to its enormous technological im- portance. Also from the physics point of view sil- icon is a very interesting material for its rich structural properties which to a large extent ap- pear because of covalent bonding between silicon atoms. Of these structural properties mechanical be- haviour of a silicon crystal strained to maximum tensile stress can in principle be understood in terms of its expected elastic nature [1] and electron energy band gap [2]. However, to understand the dynamics of these properties or to increase accu- racy of calculating them numerically can be com- putationally very demanding, since the electronic eects during structure deformations need to be handled. One of the reasons to simulate these complicated structural and fracture properties atomistically is to improve the predictivity of continuum models used mostly in engineering. In order to satisfy some of these goals in the study of structural properties of materials one can use so-called empirical interaction models or model potentials, which are made to reproduce ab initio results. The dynamical part of such a study, is handled by implementing the model potential www.elsevier.com/locate/commatsci Computational Materials Science 17 (2000) 336±342 * Corresponding author. Tel.: +358-9-451-4833; fax: +358-9- 451-4830. E-mail address: mmakijas@1ce.hut.® (M. Ma Èki-Jaskari). 0927-0256/00/$ - see front matter Ó 2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 7 - 0 2 5 6 ( 0 0 ) 0 0 0 4 8 - 3