Computational study of the Rayleigh light scattering properties of atmospheric pre-nucleation clusters

Elm, Jonas; Norman, Patrick; Bilde, Merete; Mikkelsen, Kurt V.

doi:10.1039/c4cp01206b

Cited by 43 publications

(70 citation statements)

References 81 publications

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“…43,72 The depolarization ratios α ̅ and anisotropic polarizabilities Δα are very much size dependent, which is consistent with the study of sulfuric acid hydration systems. 72 The influence of different numbers of the sulfuric acid molecules on the Rayleigh light scattering can be observed from the different lines with different colors in Figures 8−11. The Rayleigh light scattering intensities R n and isotropic mean polarizabilities α ̅ increase with increasing numbers of sulfuric acid molecules, which is consistent with the influence of the water molecules.…”

Section: ■ Methodssupporting

confidence: 68%

Properties and Atmospheric Implication of Methylamine–Sulfuric Acid–Water Clusters

Miao

et al. 2015

J. Phys. Chem. A

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The presence of amines can increase aerosol formation rates. Most studies have been devoted to dimethylamine as the representative of amine; however, there have been a few works devoted to methylamine. In this study, theoretical calculations are performed on CH3NH2(H2SO4)m(H2O)n (m = 0-3, n = 0-3) clusters. In addition to the structures and energetics, we focused on determining the following characteristics: (1) the growth mechanism, (2) the hydrate distributions and the influences of humidity and temperature, (3) Rayleigh scattering properties. We explored the cluster growth mechanism from a thermodynamics aspect by calculating the Gibbs free energy of adding a water or sulfuric acid molecule step by step at three atmospherically relevant temperatures. The relative ease of the reaction at each step is discussed. From the analysis of hydrate distributions, we find that CH3NH2(H2SO4)(H2O)2, CH3NH2(H2SO4)2, and CH3NH2(H2SO4)3 are most likely to exist in the atmosphere. The general trend of hydration in all cases is more extensive with the growing relative humidity (RH), whereas the distributions do not significantly change with the temperature. Analysis of the Rayleigh scattering properties showed that both H2SO4 and H2O molecules could increase the Rayleigh scattering intensities and isotropic mean polarizabilities, with greater influence by the sulfuric acid molecules. This work sheds light on the mechanism for further research on new particle formation (NPF) containing methylamine in the atmosphere.

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Section: ■ Methodssupporting

confidence: 68%

Properties and Atmospheric Implication of Methylamine–Sulfuric Acid–Water Clusters

Miao

et al. 2015

J. Phys. Chem. A

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“…66 The benchmark for the smallest clusters of H 2 SO 4 -NH 3 -H 2 O was determined by Elm et al 84 They found that CAM-B3LYP/aug-cc-pVDZ gave a good balance between efficiency and accuracy and obtained good agreement with both experimental and CCSD(T) values of polarizability. The light scattering intensities and isotropic mean polarizabilities a, as well as anisotropic polarizabilities Da, were calculated at the CAM-B3LYP/ aug-cc-pVDZ level of theory and the relevant computational methods are given in our earlier study.…”

Section: Methodsmentioning

confidence: 99%

On the properties and atmospheric implication of amine-hydrated clusters

et al. 2015

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Amines have been recognized as important precursor species in the formation of new atmospheric particles. Although dimethylamine-water clusters have been the focus of a large number of theoretical studies during the last few years, some information regarding these clusters, such as the influence of temperature, the analysis of their weak interactions, and their Rayleigh scattering properties, is still lacking. In this study, the equilibrium geometric structures and thermodynamics of (CH 3 ) 2 NH(H 2 O) n (n ¼ 1-6) clusters were systematically investigated using density functional theory (PW91PW91) coupled with the 6-311++G(3df,3pd) basis set. To determine the most stable isomer and the order of the different isomers, single-point calculations were executed using a two-point extrapolation method in conjunction with the complete basis set for all isomers. The optimized structures show that the addition of a fifth water molecule changes the most stable configuration from a quasi-planar ring structure to a cage-like configuration. Electron density analysis shows that the interactions of these complexes are mainly medium hydrogen bonds. The dependence on temperature of the conformational population and the Gibbs free energies of the (CH 3 ) 2 NH(H 2 O) n (n ¼ 1-6) clusters were determined with respect to temperature (200-300 K). A weak dependence on temperature was found for the formation of (CH 3 ) 2 NH(H 2 O) n (n ¼ 1-6) clusters. Dimethylamine-water clusters are favorable at low temperatures, but these clusters may be difficult to form because of the combined effect of Gibbs free energies with small negative values and the low relative concentration of dimethylamine in various atmospheric conditions, and this implies that dimethylamine-water clusters are difficult to form spontaneously in the atmosphere. Finally, the Rayleigh scattering properties of (CH 3 ) 2 NH(H 2 O) n (n ¼ 1-6) have been investigated systematically for the first time.

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“…40 All presented calculated optical properties are given in atomic units (a.u.). These were obtained by adding acid-base pairs to the existing cluster structures and minimizing using an on-the-fly MMFF94 force field using a simulating annealing approach while keeping the cluster as spherical as possible.…”

Section: Computational Methodologymentioning

confidence: 99%

“…Currently, very little is known about the direct atmospheric impact of these clusters and due to the high concentrations the Rayleigh light scattering properties of this background pool of molecular clusters might not be negligible. 40 This approach makes it possible to investigate non-spherical particles. While nucleation is currently believed to occur via the formation of small molecular clusters, very little is known about the exact mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Rayleigh light scattering properties of atmospheric molecular clusters consisting of sulfuric acid and bases

Elm

Norman

Mikkelsen

2015

Phys. Chem. Chem. Phys.

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The Rayleigh light scattering properties of (H2SO4)a(NH3)b and (H2SO4)a((CH3)2NH)b atmospheric molecular clusters have been investigated using a response theory approach. Using density functional theory the molecular structures and stepwise formation free energies of clusters with a and b up to 4 have been re-investigated. The Rayleigh scattering intensities are calculated from the dipole polarizability tensor α using the CAM-B3LYP functional by applying linear response methods. The intrinsic scattering properties of (H2SO4)a(NH3)b and (H2SO4)a((CH3)2NH)b indicate that amine containing clusters scatter light significantly more efficiently then their ammonia containing counterparts. Using the Atmospheric Cluster Dynamics Code (ACDC) the steady state cluster concentrations are estimated and the effective scattering is calculated. The effective scattering is shown to be highly dependent on the estimated concentrations and indicates that there exist competitive pathways, such as nucleation and coagulation, which influence the cluster distributions. The frequency dependence of the scattering is found to depend on the cluster composition and show increased responses when clusters contain more bases than acid molecules. Based on structures obtained using semi-empirical molecular dynamics simulations the Rayleigh scattering properties of clusters with up to 20 acid-base pairs are evaluated. This study represents the first step towards gaining a fundamental understanding of the scattering properties of small atmospheric clusters in the ambient atmosphere.

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Computational study of the Rayleigh light scattering properties of atmospheric pre-nucleation clusters

Cited by 43 publications

References 81 publications

Properties and Atmospheric Implication of Methylamine–Sulfuric Acid–Water Clusters

Properties and Atmospheric Implication of Methylamine–Sulfuric Acid–Water Clusters

On the properties and atmospheric implication of amine-hydrated clusters

Rayleigh light scattering properties of atmospheric molecular clusters consisting of sulfuric acid and bases

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