A 3D particle Monte Carlo approach to studying nucleation

Christoph Köhn*, Martin Bødker Enghoff, Henrik Svensmark

*Corresponding author for this work

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Abstract

The nucleation of sulphuric acid molecules plays a key role in the formation of aerosols. We here present a three dimensional particle Monte Carlo model to study the growth of sulphuric acid clusters as well as its dependence on the ambient temperature and the initial particle density. We initiate a swarm of sulphuric acid–water clusters with a size of 0.329 nm with densities between 107 and and 108 cm-3 at temperatures between 200 and 300 K and a relative humidity of 50%. After every time step, we update the position of particles as a function of size-dependent diffusion coefficients. If two particles encounter, we merge them and add their volumes and masses. Inversely, we check after every time step whether a polymer evaporates liberating a molecule. We present the spatial distribution as well as the size distribution calculated from individual clusters. We also calculate the nucleation rate of clusters with a radius of 0.85 nm as a function of time, initial particle density and temperature. The nucleation rates obtained from the presented model agree well with experimentally obtained values and those of a numerical model which serves as a benchmark of our code. In contrast to previous nucleation models, we here present for the first time a code capable of tracing individual particles and thus of capturing the physics related to the discrete nature of particles.
Original languageEnglish
JournalJournal of Computational Physics
Volume363
Pages (from-to)30-38
ISSN0021-9991
DOIs
Publication statusPublished - 2018

Bibliographical note

©2018 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license. (http://creativecommons.org/licenses/by/4.0/).

Keywords

  • Aerosols
  • Diffusion approach
  • Evaporation
  • Monte Carlo particle modelling
  • Nucleation
  • Size distribution

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