Characterization of molecular diffusion in liquids with dissolved gases

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The proposed research project should contribute to a fundamental understanding of molecular diffusion in binary systems consisting of liquids and dissolved gases. For the characterization of molecular diffusion, both dynamic light scattering (DLS) experiments and Molecular Dynamics (MD) simulations should be used in connection with systematically selected gas-liquid systems. Investigating such fluids at macroscopic thermodynamic equilibrium, both methods make use of microscopic fluctuations. The temporal behavior of these fluctuations is governed by the transport coefficients self-diffusivity, Maxwell-Stefan diffusivity, and mutual diffusivity. The mutual diffusivities determined by DLS from the bulk of fluids serve to verify the results from MD simulations while the latter support the interpretation of the DLS data by providing close insight into the molecular fluid structures. To get comprehensive information on the molecular diffusion of gases in liquids, auspicious combinations of liquids and gases with varying molecular sizes and interactions and covering a wide range of mixture viscosities should be studied over broad ranges of temperature and composition. The DLS experiments and MD simulations should not only provide a reliable database of diffusivities for such systems. Above all, the results should be used for analyzing how molecular diffusion is influenced by the physical characteristics of the mixture components. The performance of MD simulations regarding the prediction of mutual diffusivities should be tested by comparison with the experimental results. For this, the Maxwell-Stefan diffusivity and the thermodynamic factor have to be calculated independently. With the MD simulation results, it can also be proven how the different diffusivities are related to each other for the studied systems. Furthermore, the knowledge obtained from the proposed DLS experiments and MD simulations should contribute to the development of a simple predictive engineering model for the mutual diffusivity of binary mixtures of liquids with dissolved gases.