Phase State, Surface Tension, Water Activity, and Accommodation Coefficient of Water-Organic Clusters Near the Critical Size for Atmospheric New Particle Formation

Xiaohan Li, Ian C. Bourg

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Interactions between water and organic molecules in sub-4 nm clusters play a significant role in the formation and growth of secondary organic aerosol (SOA) particles. However, a complete understanding of the relevant water microphysics has not yet been achieved due to challenges in the experimental characterization of soft nuclei. Here, we use molecular dynamics simulations to study the phase-mixing states, surface tension, water activity, and water accommodation coefficient of organic-water clusters representative of freshly nucleated SOA particles. Our results reveal large deviations from the behavior expected based on continuum theories. In particular, the phase-mixing state has a strong dependence on cluster size; surface tension displays a minimum at a specific organic-water mass ratio (morg/mw ∼ 4.5 in this study) corresponding to a minimum inhibition of droplet nucleation associated with the Kelvin effect; and the water accommodation coefficient increases by a factor of 2 with nanocluster hygroscopic growth, in agreement with recent experimental studies. Overall, our results yield parametric relations for water microphysical properties in sub-4 nm clusters and provide insight into the role of water in the initial stages of SOA nucleation and growth.

Original languageEnglish (US)
Pages (from-to)13092-13103
Number of pages12
JournalEnvironmental Science and Technology
Volume57
Issue number35
DOIs
StatePublished - Sep 5 2023

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • Environmental Chemistry

Keywords

  • dicarboxylic acid
  • hygroscopicity
  • mass accommodation coefficient
  • molecular dynamics simulations
  • new particle formation
  • organic aerosol
  • water microphysics

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