Quantitative description of self-, Maxwell-Stefan, and Fick diffusion coefficients in sucrose and citric acid solution based on molecular dynamics simulations

H Bao and C Zhang and SL Pan and ZC Zhang and Y Yang and SP Li and YS Wang and A Wiedensohler, PHYSICS OF FLUIDS, 37, 052013 (2025).

DOI: 10.1063/5.0268503

The diffusion coefficient plays a crucial role in predicting the equilibration timescale of atmospheric aerosol particles, however current knowledge on the subject remains limited. In this study, the self-, Maxwell-Stefan, and Fick diffusion coefficients in sucrose (SC) and citric acid (CA) solution are investigated using the molecular dynamics (MD) method. Key aspects include comparisons with experimental and theoretical models, as well as the effects of temperature and solute concentration on diffusion coefficients. The results demonstrate that MD results align well with experimental data. Additionally, the McCarty- Mason equation and the Darken equation generally underpredict the self- and Maxwell-Stefan diffusion coefficients, respectively. The self-, Maxwell-Stefan, and Fick diffusion coefficients in SC and CA solutions exhibit a positive correlation with temperature and a negative correlation with solute mass fraction. Furthermore, the intensity of these influences varies: the impact of solute mass fraction on diffusion coefficients decreases with increasing temperature, while the effect of temperature diminishes with higher solute concentrations. Moreover, based on the MD simulation results, fitting formulas for the diffusion coefficients are also developed. This study underscores the value of the MD simulation method in accurately describing diffusion coefficients in solutions containing complex components.

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