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Computer Simulation Studies of Deformation Mechanisms of Amorphous Solid

Investigator: Nima Hamidi Siboni -- Advisor: Dierk Raabe

Outline

The study of the mechanical and the magnetic properties of amorphous materials has been recently the subject of intense research efforts. In this project, our focus is on the understanding of the plastic deformation mechanism(s) of the amorphous materials which is of interest from both the theoretical and the practical perspectives. As the amorphous materials lack the long-range order of the crystalline materials, it is not possible to apply the well-established elasticity and the plasticity theories which rely on the periodicity of the microscopic structure. Although the underlying structure of the amorphous materials is disordered, it is not random; it shows a short range order which is typical of liquids. In spite of this similarity between these two categories of materials, the non-trivial spatio-temporal fluctuations, i.e. the dynamical heterogeneity, plays an essential role in glass forming materials. As an example, these fluctuations, i.e. the difference between the environments experienced by each particle, are known to be responsible for the emergence of the inhomogeneous elastic modulus. In order to study the mechanical response of the amorphous materials, different theoretical approaches ranging from atomic scale, e.g. ab-initio calculations, to macroscopic scale, e.g. FEM analysis of non-Newtonian rheology, are employed. The approach adopted here is the event-driven molecular dynamics simulation of hard-sphere systems. Molecular dynamics simulation is a valuable tool as it provides detailed information about the microstate of the system as well as its temporal evolution. Such information enables us to deal with the open questions in this area e.g. the structure that carry the dynamical heterogeneities, the nature of relaxation, or the aging phenomenon.

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