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RESEARCH PRODUCT

Phase Behavior and Microscopic Transport Processes in Binary Metallic Alloys: Computer Simulation Studies

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In a binary liquid mixture, different kinds of phase transitions can occur that are associated with various mass transport phenomena in the liquid. First, there is the possibility that the liquid undergoes a liquid-liquid demixing transition [1]. Near the critical point of this transition, a slowing down of dynamic properties is observed which is characterized, e.g., by a vanishing interdiffusion coefficient at the critical point [2, 3]. Another possible phase transition is a first-order transition of the liquid into a crystalline structure. In this case, crystal nucleation and growth are limited by the diffusive transport in the liquid [1, 4]. In a binary liquid, crystal nucleation processes can be so slow that crystallization processes are inhibited on an experimental time scale. Then, the liquid solidifies into a metastable glass state, where one finds a structure that is very similar to that of the liquid. Towards the glass transition, transport properties such as diffusion coefficients or the shear viscosity exhibit a drastic change by many orders of magnitude in a relatively small temperature range. The detailed understanding of the glass transition is still one of the challenging problems in condensed matter physics [5]. The Molecular Dynamics (MD) simulation method [6, 7] is an ideal tool to study the interplay between transport processes and the aforementioned phase transitions. In a MD simulation, Newton’s equations of motion are solved for an interacting many-particle system, yielding the trajectories of all the particles, i.e. the positions and velocities of the particles as a function of time. From the trajectories, any quantity of interest can be computed, in particular static and dynamic correlation functions as well as transport coefficients. This provides insight into mechanisms of structure formation, transport and phase behavior on a microscopic scale. In this work, MD simulations of differentmodel systems are used to elucidate the role of mass transport with respect to critical slowing down, glassy dynamics and crystallization from the melt.