engleski

Complex disorder in binary mixtures: Analysis of the thermodynamic factor

Molecular dynamics simulations were used to study binary mixtures which exhibit a specific structural organization. We distinguish complex disorder, defined by the presence of microheterogeneous spatial associations of molecules and simple disorder, which characterizes totally homogeneous mixtures. These structural properties are related to the behavior of the Kirkwood-Buff integrals (KBI). The KBI are defined as integrals of radial distribution functions and, as such can be obtained from computer simulations. Equally, they can be measured using thermodynamic properties, such as partial molar volumes, compressibility and partial derivative of the chemical potential with respect to concentration. The latter is called thermodynamic factor and is a quantity of a particular interest, since it is an indicator of the stability of a mixture with respect to mixing or demixing. Here we verify the reliability of the two different approaches: the calculation of thermodynamic factor from KBI and from the excess Gibbs free energy. We start with a simple system, two component Lennard-Jones mixture and advance to more realistic models, such as alcohol + benzene mixtures. The results show that the two methods qualitatively agree.

binary-mixtures ; complex-disorder ; thermodynamic-factor ; molecular-dynamics

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