Molecular Dynamics Simulation of the Soret Effect on Two Binary Liquid Solutions with Equimolar <i>n</i>-Alkane Mixtures

Zhong, Jun; Zhao, Renbao; Ou‐Yang, Wei; Xu, Shenghua

doi:10.1021/acsomega.1c04926

Cited by 3 publications

(1 citation statement)

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“…The computations are based on the trajectory of the particles, obtained by integrating Newton’s equation of motion, and the use of a force field to represent the interaction potential between particles. Molecular dynamics simulations have been employed to compute thermodiffusion in systems containing hydrocarbons, − Lennard-Jones fluids, ,,− confined fluids, ,, associating liquids, ,− electrolytes in aqueous solution, − and silicate liquids …”

Section: Introductionmentioning

confidence: 99%

Thermodiffusion of CO₂ in Water by Nonequilibrium Molecular Dynamics Simulations

2023

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The components of a fluid mixture may segregate due to the Soret effect, a coupling phenomenon in which mass flux can be induced by a thermal gradient. In this work, we evaluate systematically the thermodiffusion of the CO 2 −H 2 O mixture, and the influence of the geothermal gradient on CO 2 segregation in deep saline aquifers in CO 2 storage. The eHeX method, a nonequilibrium molecular dynamics simulation approach, is judiciously selected to simulate the phenomenon. At 350 K, 400 bar, and CO 2 mole fraction of 0.02 (aquifer conditions), CO 2 accumulates on the cold side, and the thermal diffusion factor is close to 1 in a number of force fields. The lower the temperature, the higher is the separation and the thermal diffusion factor. In colder regions, water self-association is stronger, whereas the CO 2 −H 2 O cross-association and the CO 2 −CO 2 interactions enhance at higher temperatures. Thermodiffusion and gravitational segregation have opposite effects on CO 2 segregation. At typical subsurface conditions, the Soret effect is more pronounced than gravity segregation, and CO 2 concentrates in the top (colder region). Our work sets the stage to model the effect of electrolytes on CO 2 segregation in subsurface aquifers and other areas of interest.

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Section: Introductionmentioning

confidence: 99%

Thermodiffusion of CO₂ in Water by Nonequilibrium Molecular Dynamics Simulations

2023

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Computer modeling of thermotransport in a uniform binary liquid solution with equimolar n-alkane mixtures

Zhong,

2023

Physics of Fluids

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By means of molecular dynamics (MD), two novel methods, a thermal mean-path that may outline temperature profiles effectively in the MD system and a modified coarse-grained force field potential (the MCG-FFP) that may depict inter/intra-molecular interactions fairly well among n-alkane species, are employed to simulate a thermotransport process in a uniform liquid solution with two equimolar n-pentane (nC-5) and n-decane (nC-10) mixtures. In addition, all the MD simulations are running under two constraints: a weak thermal gradient exerting on the MD system from its hot through cold boundary sides and the standard-state acting on the MD system from its outer environment. During the whole MD simulations, coefficients of thermal diffusion and mass mutual diffusion, and the Soret coefficient (SC) for the MD system are calculated by using the MCG-FFP. As a result, the MD simulations indicate that nC-5 species with light molar-mass would migrate toward the hot boundary region, while nC-10 species with heavy molar-mass would migrate toward the cold one. Coefficients calculated from the MCG-FFP are found to meet relevant experimental outputs fairly well. Furthermore, an empirical formula developed by means of relevant continuum methods is used for calculating coefficients of mass mutual diffusion in solutions mixing with multimolar nC-5 and nC-10 species. Its one output is found to corroborate pretty well with that from the MD simulations. This may expect that such the formula would perform universally when characterizing properties of mass mutual diffusion in binary liquid solutions with other multimolar alkane mixtures in the petroleum engineering.

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Predicting the artificial dynamical acceleration of binary hydrocarbon mixtures upon coarse-graining with roughness volumes and simple averaging rules

Meinel,

Müller-Plathe

2024

The Journal of Chemical Physics

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Coarse-grained (CG) molecular models greatly reduce the computational cost of simulations allowing for longer and larger simulations, but come with an artificially increased acceleration of the dynamics when compared to the parent atomistic (AA) simulation. This impedes their use for the quantitative study of dynamical properties. During coarse-graining, grouping several atoms into one CG bead not only reduces the number of degrees of freedom but also reduces the roughness on the molecular surfaces, leading to the acceleration of dynamics. The RoughMob approach [M. K. Meinel and F. Müller-Plathe, J. Phys. Chem. B 126(20), 3737–3747 (2022)] quantifies this change in geometry and correlates it to the acceleration by making use of four so-called roughness volumes. This method was developed using simple one-bead CG models of a set of hydrocarbon liquids. Potentials for pure components are derived by the structure-based iterative Boltzmann inversion. In this paper, we find that, for binary mixtures of simple hydrocarbons, it is sufficient to use simple averaging rules to calculate the roughness volumes in mixtures from the roughness volumes of pure components and add a correction term quadratic in the concentration without the need to perform any calculation on AA or CG trajectories of the mixtures themselves. The acceleration factors of binary diffusion coefficients and both self-diffusion coefficients show a large dependence on the overall acceleration of the system and can be predicted a priori without the need for any AA simulations within a percentage error margin, which is comparable to routine measurement accuracies. Only if a qualitatively accurate description of the concentration dependence of the binary diffusion coefficient is desired, very few additional simulations of the pure components and the equimolar mixture are required.

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Molecular Dynamics Simulation of the Soret Effect on Two Binary Liquid Solutions with Equimolar n-Alkane Mixtures

Cited by 3 publications

References 50 publications

Thermodiffusion of CO₂ in Water by Nonequilibrium Molecular Dynamics Simulations

Thermodiffusion of CO₂ in Water by Nonequilibrium Molecular Dynamics Simulations

Computer modeling of thermotransport in a uniform binary liquid solution with equimolar n-alkane mixtures

Predicting the artificial dynamical acceleration of binary hydrocarbon mixtures upon coarse-graining with roughness volumes and simple averaging rules

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Molecular Dynamics Simulation of the Soret Effect on Two Binary Liquid Solutions with Equimolar n-Alkane Mixtures

Cited by 3 publications

References 50 publications

Thermodiffusion of CO2 in Water by Nonequilibrium Molecular Dynamics Simulations

Thermodiffusion of CO2 in Water by Nonequilibrium Molecular Dynamics Simulations

Computer modeling of thermotransport in a uniform binary liquid solution with equimolar n-alkane mixtures

Predicting the artificial dynamical acceleration of binary hydrocarbon mixtures upon coarse-graining with roughness volumes and simple averaging rules

Contact Info

Product

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Thermodiffusion of CO₂ in Water by Nonequilibrium Molecular Dynamics Simulations

Thermodiffusion of CO₂ in Water by Nonequilibrium Molecular Dynamics Simulations