Effects of oxidation on the nanoscale mechanisms of crack formation in aluminum.

Materials failure, in the form of cracking, is a phenomenon of fundamental scientific interest and one that impacts a variety of applications spanning a wide range of fields, particularly those of materials science and engineering. Experiments have investigated extensively the macroscopic properties associated with cracking within homogeneous materials as well as at interfaces between dissimilar materials. Likewise, theoretical modeling via engineering finite-element approaches and molecular dynamics simulations with empirical embedded-atom potentials 3] have provided some insight into cracking mechanisms. Nevertheless, these models rely on inherent assumptions concerning interatomic and/or bulk behavior, a drawback in instances where fundamental atomic interactions are poorly understood or improperly characterized by overly simplified model potentials. A comprehensive study incorporating a first principles approach at the atomic scale and effectively linking this information to the macroscopic scale poses an array of challenges, implementational and otherwise. To date, these difficulties and the computational expense associated with first principles calculations have generally motivated employing empirical assumptions to treat mechanics of the smallest length-scale regime. Resorting to empirical models limits the chemistry that may be accounted for. Accordingly, despite widespread scientific interest in the cracking phenomenon, aspects of the microscopic failure mechanisms remain largely a mystery. Herein, we investigate some aspects of the atomic-level properties which lead to chemically induced crack formation within a simple model. 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