ナノ構造シミュレーションにおける原子配置変化を用いる微視的なひずみの解析

概要

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The simple method to analyze atomistic strain in molecular dynamics (MD) simulation is studied. The proposed method, here called atomic strain measure (ASM), is based on Green-Lagrangian strain measure which is traditionally defined in continuum mechanics. The ASM is formulated for the use in atomic system with some adequate assumptions. In our formulation, pairwise interatomic vectors of finite length are approximately substituted for infinitesimal continuum line segments between material's points. The obtained expression of ASM is very simple and easy to use. The authors are checking the validity, limitation and usefulness of ASM by actual MD models of aluminum. A perfect-crystal model results in qualitatively good results for strain evaluation, as for the response to homogenous deformation. The ASM is also applied to a polycrystal model, which has a lot of inhomogeneous nanostructures, i.e. crystalline defects such as grain boundaries (GBs) and triple junctions (TJs) among them. It is confirmed that a certain concentration of strain onto the vicinity of GB plane or TJ point is able to be clearly captured by using ASM. It is concluded that approach of the present ASM analysis for atomic simulation is very effective to obtain change of nanostructure.