ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-11-519-2011 Glycine in aerosol water droplets: a critical assessment of Köhler theory by predicting surface tension from molecular dynamics simulations Li X. 1 3 Hede T. 2 Tu Y. 4 Leck C. 2 Ågren H. 1 Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, 10691 Stockholm, Sweden Department of Meteorology, Stockholm University, 10691 Stockholm, Sweden Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, China School of Science and Technology, Örebro University, 70182 Örebro, Sweden 18 01 2011 11 2 519 527 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/11/519/2011/acp-11-519-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/519/2011/acp-11-519-2011.pdf

Aerosol particles in the atmosphere are important participants in the formation of cloud droplets and have significant impact on cloud albedo and global climate. According to the Köhler theory which describes the nucleation and the equilibrium growth of cloud droplets, the surface tension of an aerosol droplet is one of the most important factors that determine the critical supersaturation of droplet activation. In this paper, with specific interest to remote marine aerosol, we predict the surface tension of aerosol droplets by performing molecular dynamics simulations on two model systems, the pure water droplets and glycine in water droplets. The curvature dependence of the surface tension is interpolated by a quadratic polynomial over the nano-sized droplets and the limiting case of a planar interface, so that the so-called Aitken mode particles which are critical for droplet formation could be covered and the Köhler equation could be improved by incorporating surface tension corrections.

 References Alejandre, J., Tildesley, D. J., and Chapela, G. A.: Molecular dynamics simulation of the orthobaric densities and surface tension of water, J. Chem. Phys., 102, 4574–4583, 1995. Berendsen, H. J. C., Grigera, J. R., and Straatsma, T. P.: The missing term in effective pair potentials, J. Phys. Chem., 91, 6269–6271, 1987. Blanchard, D. C.: The oceanic production of volatile cloud nuclei, J. Atmos. Sci., 28, 811–812, 1971. Blanchard, D. C. and Syzdek, L. D.: Film drop production as a function of bubble size, J. Geophys. Res., 93, 3649–3654, 1988. Block, B. J., Das, S. K., Oettel, M., Virnau, P., and Binder, K.: Curvature dependence of surface free energy of liquid drops and bubbles: A simulation study, J. Chem. Phys., 133, 154702, doi:10.1063/1.3493464, 2010. Blokhuis, E. M., Bedeaux, D., Holcomb, C. D., and Zollweg, J. A.: Tail corrections to the surface tension of a Lennard-Jones liquid-vapour interface, Mol. Phys., 85, 665–669, 1995. Brodskaya, E. N., Eriksson, J. C., Laaksonen, A., and Rusanov, A. I.: Local Structure and work of formation of water clusters studied by molecular dynamics simulations, J. Colloid Interface Sci., 180, 86–97, 1996. Bull, H. B. and Breese, K.: Surface tension of amino acid solutions: a hydrophobicity scale of the amino acid residues, Arch. Biochem. Biophys., 161, 665–670, 1974. Chen, F. and Smith, P. E.: Simulated surface tensions of common water models, J. Chem. Phys., 126, 221101, doi:10.1063/1.2745718, 2007. Darden, T., York, D., and Pedersen, L.: Particle mesh Ewald: An N-log(N) method for Ewald sums in large systems, J. Chem. Phys., 98, 10089–10092, 1993. Essmann, U., Perera, L., Berkowitz, M. L., Darden, T., Lee, H., and Pedersen, L. G.: A smooth particle mesh Ewald method, J. Chem. Phys., 103, 8577–8592, 1995. Facchini, M. C., Mircea, M., Fuzzi, S., and Charlson, R. J.: Cloud albedo enhancement by surface-active organic solutes in growing droplets, Nature, 401, 257–259, 1999. Hess, B.: P-LINCS: A parallel linear constraint solver for molecular simulation, J. Chem. Theory Comput., 4, 116–122, 2008. Hess, B., Bekker, H., Berendsen, H. J. C., and Fraaije, J. G. E. M.: LINCS: A linear constraint solver for molecular simulations, J. Comput. Chem., 18, 1463–1472, 1997. Hess, B., Kutzner, C., van der Spoel, D., and Lindahl, E.: GROMACS 4: Algorithms for highly efficient, load-balanced, and scalable molecular simulation, J. Chem. Theory Comput., 4, 435–447, 2008. Hoover, W. G.: Canonical dynamics: equilibrium phase-space distributions, Phys. Rev. A, 31, 1695–1697, 1985. Irving, J. H. and Kirkwood, J. G.: The statistical mechanical theory of transport processes. IV. The equations of hydrodynamics, J. Chem. Phys., 18, 817–829, 1950. Jorgensen, W. L., Maxwell, D. S., and Tirado-Rives, J.: Development and testing of the OPLS all-atom force field on conformational energetics and properties of organic liquids, J. Am. Chem. Soc., 118, 11225–11236, 1996. Julin, J., Napari, I., Merikanto, J., and Vehkamäki, H.: A thermodynamically consistent determination of surface tension of small Lennard-Jones clusters from simulation and theory, J. Chem. Phys., 133, 044704, doi:10.1063/1.3456184, 2010. Kristensson, A., Rosenørn, T., and Bilde, M.: Cloud droplet activation of amino acid aerosol particles, J. Phys. Chem. A, 114, 379–386, 2010. Köhler, H.: The nucleus in and the growth of hygroscopic droplets, Trans. Faraday Soc., 32, 1152–1161, 1936. Li, X., Hede, T., Tu, Y., Leck, C., and $\rm \mathringA$gren, H.: Surface-active cis-pinonic acid in atmospheric droplets: A molecular dynamics study, J. Phys. Chem. Lett., 1, 769–773, 2010. McGraw, R. and Laaksonen, A.: Scaling properties of the critical nucleus in classical and molecular-based theories of vapor-liquid nucleation, Phys. Rev. Lett., 76, 2754–2757, 1996. Mopper, K. and Zika, R. G.: Free amino acids in marine rains: evidence for oxidation and potential role in nitrogen cycling, Nature, 325, 246–249, 1987. Nosé, S.: A molecular dynamics method for simulations in the canonical ensemble, Mol. Phys., 52, 255–268, 1984. Pappenheimer, J. R., Lepie, M. P., and Wyman Jr., J.: The surface tension of aqueous solutions of dipolar ions, J. Am. Chem. Soc., 58, 1851–1855, 1936. Ramanathan, V., Cess, R. D., Harrison, E. F., Minnis, P., Barkstrom, B. R., Ahmad, E., and Hartmann, D.: Cloud-radiative forcing and climate: Results from the Earth radiation budget experiment, Science, 243, 57–63, 1989. Sampayo, J. G., Malijevsk\'y, A., Müller, E. A., de Miguel, E., and Jackson, G.: Communications: Evidence for the role of fluctuations in the thermodynamics of nanoscale drops and the implications in computations of the surface tension, J. Chem. Phys., 132, 141101, doi:10.1063/1.3456184, 2010. Saxena, V. K.: Evidence of the biogenic nuclei involvement in antarctic coastal clouds, J. Phys. Chem., 87, 4130–4134, 1983. Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K. B., Tignor, M., and Miller, H. L. (eds.): Climate Change 2007: The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 2007. Sun, J. and Ariya, P. A.: Atmospheric organic and bio-aerosols as cloud condensation nuclei (CCN): a review, Atmos. Environ., 40, 795–820, 2006. Thompson, S. M., Gubbins, K. E., Walton, J. P. R. B., Chantry, R. A. R., and Rowlinson, J. S.: A molecular dynamics study of liquid drops, J. Chem. Phys., 81, 530–542, 1984. Tolman, R. C.: The effect of droplet size on surface tension, J. Chem. Phys., 17, 333–337, 1949. Twomey, S.: Pollution and the planetary albedo, Atmos. Environ., 8, 1251–1256, 1974. van der Spoel, D., Lindahl, E., Hess, B., van Buuren, A. R., Apol, E., Meulenhoff, P. J., Tieleman, D. P., Sijbers, A. L. T. M., Feenstra, K. A., van Drunen, R., and Berendsen, H. J. C.: Gromacs User Manual version 4.0, www.gromacs.org, 2005. van Giessen, A. E. and Blokhuis, E. M.: Direct determination of the Tolman length from the bulk pressures of liquid drops via molecular dynamics simulations, J. Chem. Phys., 131, 164705, doi:10.1063/1.3253685, 2009. Zakharov, V. V., Brodskaya, E. N., and Laaksonen, A.: Surface tension of water droplets: A molecular dynamics study of model and size dependencies, J. Chem. Phys., 107, 10675–10683, 1997.