Oxidation of aluminum nanoclusters

作     者：Timothy J. Campbell Gurcan Aral Shuji Ogata Rajiv K. Kalia Aiichiro Nakano Priya Vashishta 

作者机构：Collaboratory for Advanced Computing and Simulations Department of Materials Science and Engineering Department of Physics and Astronomy Department of Computer Science University of Southern California Los Angeles California 90089-0242 USA Mississippi State University Stennis Space Center Mississippi 39529 USA Graduate School of Engineering Nagoya Institute of Technology Nagoya 466-8555 Japan 

出 版 物：《Physical Review B》 (Phys. Rev. B Condens. Matter Mater. Phys.)

年 卷 期：2005年第71卷第20期

页      面：205413-205413页

核心收录：

学科分类：0808[工学-电气工程] 0809[工学-电子科学与技术（可授工学、理学学位）] 07[理学] 0805[工学-材料科学与工程（可授工学、理学学位）] 0702[理学-物理学] 

摘      要：The dynamics of oxidation of aluminum nanoclusters (20nm diameter) is investigated using a parallel molecular dynamics approach based on variable charge interatomic interactions due to Streitz and Mintmire that include both ionic and covalent effects. Simulations are performed for both canonical ensembles for molecular oxygen (O2) environments and microcanonical ensembles for molecular (O2) and atomic (O1) oxygen environments. Structural and dynamic correlations in the oxide region are calculated, as well as the evolution of charges, surface oxide thickness, diffusivities of atoms, and local stresses. In the microcanonical ensemble, the oxidizing reaction becomes explosive in both molecular and atomic oxygen environments due to the enormous energy release associated with Al−O bonding. Local stresses in the oxide scale cause rapid diffusion of aluminum and oxygen atoms. Analyses of the oxide scale reveal significant charge transfer and a variation of local structures from the metal-oxide interface to the oxide-environment interface. In the canonical ensemble, oxide depth grows linearly in time until ∼30ps, followed by saturation of oxide depth as a function of time. An amorphous oxide layer of thickness ∼40Å is formed after 466ps, in good agreement with experiments. The average mass density in the oxide scale is 75% of the bulk alumina density. Evolution of structural correlation in the oxide is analyzed through radial distribution and bond angles. Through detailed analyses of the trajectories of O atoms and their formation of OAln structures, we propose a three-step process of oxidative percolation that explains deceleration of oxide growth in the canonical ensemble.