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Elucidating the Limiting Steps in Sulfuric Acid - Base New Particle Formation Jonas Elm J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.7b08962 • Publication Date (Web): 11 Oct 2017 Downloaded from http://pubs.acs.org on October 13, 2017
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The Journal of Physical Chemistry
Elucidating the Limiting Steps in Sulfuric Acid Base New Particle Formation Jonas Elm∗ Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark E-mail:
[email protected]
∗
To whom correspondence should be addressed
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Abstract The molecular interactions between sulfuric acid (sa) and methylamine (ma) are investigated using computational methods. The molecular structures and vibrational frequencies of (sa)a (ma)b clusters, with a, b ≤ 4 were obtained with the ωB97X-D functional using a 6-31++G(d,p) basis set. The single point energies were corrected using the domain-based local pair natural orbital coupled cluster method – DLPNOCCSD(T) – with an aug-cc-pVTZ basis set. The calculated Gibbs free energies (∆G) of the clusters are used to calculate the evaporation rates of the (sa)a (ma)b cluster system and compare them to the corresponding ammonia clusters. Using the atmospheric cluster dynamics code (ACDC), the new particle formation rates of the (sa)a (ma)b clusters were simulated and compared to the (sa)a (dma)b cluster system. It is found that methylamine is not capable of explaining observed new particle formation event in the ambient atmosphere. Looking into the calculated Gibbs free energy profiles it is found that the limiting steps in forming stable (sa)3−4 (base)3−4 clusters depend strongly on the formation of the (sa)1 (base)1 and (sa)2 (base)2 clusters. These findings further support that compounds with high basicity are required to form the very initial cluster nucleus, which serves as the basis for forming new particles in the atmosphere.
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Introduction
Atmospheric ultrafine aerosol particles present a threat to human health. Inhalation of ultrafine particles can lead to an increased risk for lung cancer and cardiovascular diseases and is currently responsible for around 7 million premature deaths around the world, annually. 1 Aerosols also influence the global climate, by either absorbing or scattering incoming radiation. 2 The largest source of new aerosol particles in the atmosphere is from gas to particle transformation, but the participating vapours remain highly uncertain. Sulfuric acid concentrations can be linked directly to new particle formation events, 3 but another stabilizing constituent is needed to explain observed production rates in the ambient atmosphere. 4–6 Atmospheric bases represent one of the most important species for forming strong clusters with sulfuric acid through proton transfer reactions. Albeit being the most abundant base, ammonia does not form stable clusters with sulfuric acid and cannot explain observed new particle formation rates. 5 Highly basic amines are more likely candidates for efficiently stabilizing sulfuric acid clusters. Using computational methods Kurt´en et al. demonstrated that the enhanced stability of sulfuric acid - dimethylamine (dma) clusters compared to sulfuric acid - ammonia clusters was large enough to overcome the typical difference in atmospheric concentrations of ammonia and amines. 7 On the contrary the computational study of Nadykto et al. found the opposite conclusion. 8 The different conclusions between the two studies can be attributed to the applied computational level of theory for computing the binding energies (RI-CC2/aug-cc-pVTZ vs PW91/6-311++G(3df,3pd)). 9 The computational study by Depalma et al. on large clusters with up to 8 sulfuric acid molecules and 8 bases also found that substituting ammonia with dimethylamine in sulfuric acid clusters was energetically favourable. 10 Furthermore, Depalma and co-workers showed that water had a minor effect on the cluster energetics, with a lowering of approximately 10% depending on the cluster size and number of water molecules. 11 Experiments simulating realistic atmospheric conditions at the CLOUD chamber 12 has definitively proven that 3 pptv of dimethylamine enhance new particle formation rates up to 3
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1000-fold compared to 250 pptv of ammonia. K¨ urten et al. showed that neutral sulfuric acid - dimethylamine clustering either proceeds at or close to the kinetic limit. 13 The experiments revealed the formation of clusters containing up to 14 sulfuric acid and 16 dimethylamine molecules, corresponding to ∼2 nm in mobility diameter. These findings illustrates that in the context of forming new particles the basicity of the base can be more important than its atmospheric abundance. Recent flow reactor experiments also indicate that the potential to form new particles follow the base strength with NH3 < methylamine (ma) < dimethylamine (dma) ≤ trimethylamine (tma). 14,15 In a similar manner diamines are more basic than their corresponding monoamines and diamines, such as putrescine, has been shown to enhance new particle formation rates significantly compared to for instance dma and ma. 16–18 A recent study by Nadykto et al. compared the potential of ammonia and ma in enhancing sulfuric acid induced new particle formation 19 and they found that ma new particle formation begins to dominate over ammonia when [ma]/[NH3 ] > ∼ 10−3 . A recent computational study by Olenius et al. showed that ma behaves significantly different from dma and tma with respect to cluster growth mechanisms and hygroscopicity. 20 Although methylamine is one of the most abundant amines in the atmosphere, 21 it has been studied to a much lesser extent than ammonia and dma. This paper investigates the molecular interactions between sulfuric acid and methylamine using computational methods. The currently available thermochemical data is extended by one more cluster both along the methylamine and sulfuric acid coordinate, leading to (sa)a (ma)b clusters, with a, b ≤ 4. Employing the Atmospheric Cluster Dynamics Code (ACDC) cluster growth rates are presented and the results are compared to the sulfuric acid - dimethylamine cluster systems. The comparison allow for the determination of the limiting steps in sulfuric acid - base new particle formation.
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Methods
2.1
Compuational Details
The Gaussian 09 program, revision D.01 22 were used for all geometry optimizations and vibrational frequency calculations. As the studied cluster structures consist of acid and bases, some degree of proton transfer can be assumed. This implies that standard force field methods are not applicable for these systems, hence density functional theory was the method of choice for obtaining the structures and vibrational frequencies. Based on benchmark results on binding energies of atmospheric clusters, 23,24 the ωB97X-D 25 functional was utilized. For all the DFT calculations the 6-31++G(d,p) basis set was used as it is a good compromise between accuracy and efficiency and does not yield significant errors in the thermal contribution to the free energy compared to much larger basis sets such as 6-311++G(3df,3pd) 26 or aug-cc-pV5Z. 27 Domain-based local pair natural orbital coupled cluster calculations – DLPNO-CCSD(T) 28,29 – were calculated using the ORCA 3.0.3 program 30 with an aug-ccpVTZ basis set, using an on-the-fly local transformation (LT3). Invoking LT3 has been shown not to be any source of errors in DLPNO-CCSD(T) calculations on atmospheric clusters. 31 Low lying vibrational frequencies can be a large source of errors when calculating thermochemical parameters. The quasi-harmonic approximation was employed 32 using the freely available ”Goodvibes” python script by Funes-Ardois and Paton. 33 In the quasi-harmonic approximation the contribution from low vibrational frequencies to the entropy is replaced by a corresponding rotational entropy. Larger clusters will have more vibrational modes below the chosen cut-off value, hence more vibrational modes will be replaced by rotational entropies. The effect of the chosen cut-off value will thus depend on the size of the clusters. Based on test calculations (See Supporting Information) and recent results, 18 a vibrational frequency cut-off value of 200 cm−1 was chosen.
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2.2
Obtaining the Cluster Geometries
The molecular cluster structures consisting of sulfuric acid (sa) and methylamine (ma) are studied. Clusters up to (sa)1−3 (ma)1−3 has previously been reported in the literature, 19,20,34 and here the cluster structures are extended up to (sa)1−4 (ma)1−4 . The cluster structures were re-evaluated by including an additional new round of conformational sampling at the ωB97X-D/6-31++G(d,p) level of theory. Based on inspection of the favourable binding patterns of the existing (sa)1−3 (ma)1−3 , (sa)1−4 (ammonia)1−4 34 and (sa)1−4 (dma)1−4 18 cluster structures, ten or more new cluster structures were constructed for each cluster configuration using chemical intuition. The main part of the clusters were constructed by either adding a methyl group to ammonia or by deleting one methyl group from dimethylamine in all possible permutations. This new round of configurational sampling led to the identification of several new lower lying free energy minima than previously reported, as well as extending the existing data by one more cluster both along the methylamine and sulfuric acid coordinate.
2.3
ACDC Simulations
The new particle formation rates were simulated using the Atmospheric Cluster Dynamics Code (ACDC). 35–37 In ambient measurements the formation rate of clusters with 1.7 nm mobility diameter is used as a measure for new particle formation. 12,38,39 The clusters considered in our simulation includes up to four sulfuric acid molecules and four base molecules and the largest cluster studied measures roughly 1.5 nm in mobility diameter. A new particle is defined as a cluster which has a low enough evaporation rate to assume that it will not re-evaporate and the simulated new particle formation rate is the flux of clusters that leave the system. An additional loss term due to coagulation with larger particles was used in the simulations. Based on typical values observed in boreal forest environments, 40,41 a constant coagulation sink with a value of 2.6×10−3 s−1 was chosen.
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Results and Discussion
3.1
Cluster Structures
Figure 1 presents the lowest Gibbs free energy (sa)1−4 (ma)1−4 cluster structures, obtained at the ωB97X-D/6-31++G(d,p) level of theory. The (ma)2−4 clusters are shown in the supporting information. One very important feature in sulfuric acid - base clusters is proton transfers. The transfer of a proton from sulfuric acid to the base changes the intermolecular interactions from hydrogen bonding interactions to electrostatic interactions. This will inevitably strengthen the intermolecular interactions in the cluster, increasing its stability. There is observed a proton transfer from sulfuric acid to a methylamine in most of the cluster structures. Only in a single cluster – (sa)3 (ma)4 – is the formation of a sulfate ion (SO42– ) observed. This is very similiar to the case of (sa)a (NH3 )b clusters, where a sulfate ion is only formed in the (sa)3 (NH3 )4 and (sa)4 (NH3 )5 clusters. We previously observed the formation of a single sulfate ion in the (sa)1 (dma)4 , (sa)2 (dma)3−4 and (sa)3 (dma)4 cluster structures. 18 Based on simple acid - base principles the formation of sulfate ions in the cluster is highly dependent on the basicity of the base. This is well demonstrated by the fact that very basic diamines (putrescine, put) readily form several sulfate ions in (sa)a (put)b clusters. 18
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3.2
Cluster Free Energy Surfaces and Evaporation Rates
From the law of mass action, the concentration dependent Gibbs free energies of the clusters at a given vapour concentrations Ci can be obtained as: ∆Gactual (C1 , C2 , ..., Cn ) = ∆Gref − kB T ∑ Ni ln ( n
i=1
Ci ) Cref
(1)
Here the sum is over all compounds i in the cluster, Ni is the number of molecules of type i in the cluster, ∆Gref is the standard Gibbs free energy calculated at the reference pressure pref , kB is Boltzmann’s constant and T the temperature. The reference concentration Cref is given by Cref = pref /(kB T ). The calculated formation free energy surfaces of the (sa)1−4 (NH3 )1−4 and (sa)1−4 (ma)1−4 clusters are presented in Figure 2. The concentration of sulfuric acid was set to [H2 SO4 ] = 106 molecules cm−3 , and with a mixing ratio of 10 pptv of ma and 100 pptv of NH3 . All calculations were performed at the DLPNO-CCSD(T)/aug-cc-pVTZ//ωB97XD/6-31++G(d,p) level of theory, at 278.15 K. 65 65.74
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Figure 2: Gibbs free energy surface (in kcal/mol) of the (sa)1−4 (NH3 )1−4 clusters (left) and (sa)1−4 (ma)1−4 clusters (right), calculated at the DLPNO-CCSD(T)/aug-cc-pVTZ//ωB97XD/6-31++G(d,p) level of theory. Calculations were performed at 278.15 K, with [H2 SO4 ] = 106 molecules cm−3 and 10 ppt of methylamine and 100 pptv of ammonia. There is seen a large free energy barrier in all directions in the sulfuric acid - ammonia 9
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system. This is in good agreement with previous results obtained by Olenius et al. 37 On the contrary, the sulfuric acid - methylamine system show a low free energy barrier along the diagonal on the acid - base grid. However, in all cases the (sa)1−4 (ma)1−4 clusters have higher formation free energies compared to the (sa)1−4 (dma)1−4 clusters at similar conditions and same level theory. 18 This indicates that the free energy surface of ma and dma follow the basicity of the two amines, albeit having very similar trends in the free energy surfaces. Previous results based on RI-CC2/aug-cc-pVTZ//B3LYP/CBSB7 calculations have suggested that the free energies are lowest along the diagonal on the acid - base grid, indicating that the most stable clusters are when there is a 1:1 ratio between sulfuric acid and the amines. The experiments performed at the CLOUD chamber on sulfuric acid - ammonia 5 and sulfuric acid - dimethylamine 13 corroborates that the clusters grow along the diagonal of the system. This is further indicated by electro-spray ionization mass spectrometry experiments of ammonium sulfate solutions both in positive and negative mode. 42 The updated quantum chemical free energies calculated here for (sa)1−4 (NH3 )1−4 and (sa)1−4 (ma)1−4 and previously for (sa)1−4 (dma)1−4 clusters 18 show a slightly different picture. Indeed the free energy along the diagonal is rather low, but low free energies are also observed for the off-diagonal (sa)n+1 (base)n clusters for n up to 2. In order to stimulate pure growth along the diagonal of the system, the formation of the (sa)1 (base)1 cluster needs to be rather favourable. Depending on the basicity of the base, the formation of the sulfuric acid dimer (sa)2 is in competition with the formation of the initial (sa)1 (base)1 cluster. This is for instance the case for NH3 and ma, but not the case for dma or more basic compounds such as diamines. 18 A better way to estimate the stability is to look at the evaporation rates of the clusters. From the free energies calculated using quantum chemical methods (∆G), the total evaporation rates (∑ γ) were calculated as a sum over all the individual contributions.: 36 γ(i,j)→i,j = βi,j
∆Gi+j − ∆Gi − ∆Gj Pref exp ( ) kB T kB T 10
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Here βi,j is the collision coefficient between molecule/cluster i and j, kB is Boltmanzz’s constant, T the temperature and ∆G is the quantum mechanically calculated free energy at the reference pressure Pref . Figure 3 shows the calculated evaporation rates of the (sa)1−4 (NH3 )1−4 and (sa)1−4 (ma)1−4 cluster systems at 278.15K.
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Figure 3: Total evaporation rates (∑ γ) in s−1 of the (sa)1−4 (NH3 )1−4 clusters (left) and (sa)1−4 (ma)1−4 clusters (right) calculated at the DLPNO-CCSD(T)/aug-cc-pVTZ//ωB97XD/6-31++G(d,p) level of theory. Calculations were performed at 278.15 K The diagonal (sa)n (base)n clusters for n up to 2, have high evaporation rates for both ammonia and methylamine, with values in the range 2×102 - 6×105 s−1 . In contrast for the (sa)1 (dma)1 and (sa)2 (dma)2 clusters, low evaporation rates of 5 and 2×10−1 s−1 have been reported, respectively. 18 Thus the evaporation rates of the (sa)1 (base)1 and (sa)2 (base)2 clusters follow the basicity of the base molecules. The (sa)2 (ma)1 , (sa)3 (ma)2 , (sa)3 (ma)3 and (sa)4 (ma)4 clusters show similar magnitude in the evaporation rates as the corresponding dma containing clusters. 18 In accordance with previously studied sulfuric acid - monoamine systems, we begin to see a general trend in the evaporation rates of the clusters. The (sa)2 (base)1 , (sa)3 (base)2 , (sa)3 (base)3 and (sa)4 (base)4 clusters all have the lowest evaporation rates in the system. This suggests that the (sa)3 (base)3 and (sa)4 (base)4 clusters are relatively stable against evaporation for both ma and dma clusters and should be capable
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of growing into larger particle when formed. Thus the flux towards these clusters is the limiting step in sulfuric acid - base new particle formation. The basicity of the base will highly influence the formation of the initial (sa)n (base)n clusters for n up to 2, which in turn will govern the potential of the base to form new particles. For bases with low basicity the formation of the (sa)n (base)n clusters for n up to 2, will be a stochastic process, which involves consecutive cluster formation and re-evaporation events. For bases with high basicity, the process is barrierless and new particle formation will be at the kinetic limit.
3.3
New Particle Formation Rates
The new particle formation rates of the (sa)1−4 (ma)1−4 cluster system were simulated and the results were compared with the previously reported (sa)1−4 (dma)1−4 cluster system. The new particle formation rates for the (sa)1−4 (NH3 )1−4 system was also calculated, but at realistic atmospheric conditions literally no particles were formed. As the potential energy surface of the (sa)1−4 (ma)1−4 cluster system has very similar characteristics to the (sa)1−4 (dma)1−4 cluster system, the same criteria for when a given cluster can be allowed to grow out of the system was chosen. Hence the (sa)5 (ma)4 and (sa)5 (ma)5 clusters are considered stable against evaporation and considered a newly formed particle. The sulfuric acid concentration was varied between 105 and 108 molecules cm−3 and at a 100 pptv mixing ratio of ma. The simulations were performed at 278.15 K. Figure 4 shows the new particle formation rates compared to 10 pptv of dma (black dotted line, data taken from ref 18 ) and atmospheric observations 43–45 (gray dots).
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Figure 4: Simulated new particle formation rates (cm−3 s−1 ) as a function of sulfuric acid concentration with ma mixing ratios of 100 pptv (red), ma with a mixing ratio of 100 pptv, scaled by a factor of 10 (green) and ma with a mixing ratio of 100 pptv while lowering the free energy of the (sa)1 (ma)1 and (sa)2 (ma)2 clusters by -4.5 kcal/mol (blue). The dashed black line corresponds to dma with a mixing ratio of 10 pptv (- - -) (data taken from ref 18 ). The grey dots correspond to atmospheric observations.
The simulated new particle formation rates for the (sa)1−4 (ma)1−4 cluster system is seen to fall outside the ambient observations for mixing ratios of 100 pptv. This can be attributed to the weak formation of the (sa)1 (ma)1 and (sa)2 (ma)2 clusters and the general weaker stability of the clusters compared to the (sa)1−4 (dma)1−4 cluster system. The formation free energy profile will determine the intersection with the x-axis and to describe new particle formation rates at low sulfuric acid concentrations, stronger bases than ma is required. It is seen that the slopes of the new particle formation rates does not fit the entire range of observed new particle formation rates. In a multi-component system with different monomer concentrations and competition between different pathways the effect on the slope is not straight forward. Factors such as coagulation, cluster-cluster collisions and monomer 13
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depletion all contribute. 46 The atmospheric observations are the collective contribution of many different compounds and mechanisms, thus it is unlikely that a single component, coupled with sulfuric acid, should capture all the possible rates. It is much more likely that a large range of compounds is capable of explaining various regions of the observed new particle formation events. To look further into how the formation free energy of the (sa)1 (ma)1 and (sa)2 (ma)2 clusters affect the new particle formation rates, the cluster free energies were artificially strengthened. Figure 5 show the enhancement in new particle formation rates by lowering the free energy of the (sa)1 (ma)1 cluster, the (sa)2 (ma)2 cluster or both (sa)1 (ma)1 and
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Figure 5: Enhancement in new particle formation (NPF) rate by lowering the free energy of the (sa)1 (ma)1 cluster (left), the (sa)2 (ma)2 cluster (middle) and both the (sa)1 (ma)1 and (sa)2 (ma)2 cluster (right). Simulations were performed at 278.15 K, with [H2 SO4 ] set to 107 molecules cm−3 , and with a mixing ratio of 100pptv methylamine. Lowering the free energy of the (sa)1 (ma)1 cluster by -4.5 kcal/mol yield a 120-fold increase in the new particle formation rate. The enhancement is less profound for the (sa)2 (ma)2 cluster where a lowering of the free energy by -3 kcal/mol only yield a 8-fold increase in the new particle formation rate. This is caused by the fact that the formation of the (sa)2 (ma)2 cluster remains hindered by the weak formation of the (sa)1 (ma)1 cluster. By simultaneously lowering the free energy of the (sa)1 (ma)1 and (sa)2 (ma)2 clusters by -4.5 kcal/mol, a 1700-fold increase in the new particle formation rate is found. Lowering the formation free energy of both clusters, lead to a higher flux towards the stable 14
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(sa)3 (ma)3 cluster and thus significantly higher new particle formation rates. As depicted in Figure 4 (blue solid line), lowering the free energy of the (sa)1 (ma)1 and (sa)2 (ma)2 clusters by -4.5 kcal/mol yield new particle formation rates even higher than the sulfuric acid - dimethylamine system. These findings clearly illustrate that it is in fact the formation of the (sa)1 (base)1 and (sa)2 (base)2 clusters which hinders the formation of new particles for bases with low basicity. The temperature have a large effect on the new particle formation rates. The formation of hydrogen bonds will lead to fewer degrees of freedom in the cluster and thus a decrease in the entropy. This implies that the formation free energies will be more favourable as the temperature decreases. To quantify this effect the new particle formation rates were simulated in 10 K intervals from 258.15 K to 298.15 K with [H2 SO4 ] = 107 molecules cm−3 and 100 pptv of methylamine. Lowering the temperature from 278.15 K to 268.15 K leads to a 16-fold increase in the new particle formation rate. Lowering it further to 258.15 K leads to another 9-fold increase. Increasing the temperature to 288.15 K leads to a 50-fold decrease in the new particle formation rates. At 298.15 K, practically no particles are formed. The large temperature dependence on the new particle formation rates originates from the change in the initial (sa)1 (ma)1 and (sa)2 (ma)2 cluster formation free energies in a similar manner as shown with the artificial strengthening in Figure 5. It should be noted that hydration is neglected in the simulated new particle formation rates. Bustos and co-workers showed that the addition of 1-2 water molecules to an (sa)1 (ma)1 cluster was more favourable than for sulfuric acid alone. 47 This suggests that (sa)a (ma)b clusters might be hydrated in the ambient atmosphere. Recent studies have shown that the effect of hydration on new particle formation rates depends strongly on the basicity of the base. 20,48 New particle formation rates involving strong bases such as dma and tma are more or less unaffected by hydration, whereas weaker bases such as NH3 and ma show a stronger dependence. For ma an increase of up to one order of magnitude were observed in the new particle formation rates at 278 K, [H2 SO4 ] = 106 molecules cm−3 and
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100 pptv of methylamine, at 100% relative humidity. 20 The green line in Figure 4 represents our calculated new particle formation rate at 100 pptv mixing ratio of ma, scaled by a factor of 10 to simulate the most drastic effect of hydration. While the effect of hydration moves the simulated new particle formation rates closer in proximity to the (sa)1−4 (dma)1−4 system, hydrated (sa)1−4 (ma)1−4 clusters do not appear to be able to explain observed new particle formation rates in the atmosphere. These findings indicate that it is mainly the basicity of the base which governs its ability to form new particles with sulfuric acid. While the base is still required to be present in sufficient concentrations, such that sulfuric acid - base collisions will occur, the exponential dependence on the binding free energy significantly outweighs the linear dependence on base concentration. The formation of the (sa)1 (base)1 cluster is the most important step for the formation of new particles from sulfuric acid and bases. This further suggests that highly basic amines are indeed key species in the very initial formation of stable atmospheric prenucleation clusters. These findings are supported by a recent synopsis by Bzdek et al. which also indicated that amines are effective at assisting the initial formation of clusters, but are less important as the cluster size increases. 42 After a stable sulfuric acid - base nucleus is formed, the subsequent growth of the cluster is most likely driven by condensation of highly oxidized multifunctional compounds (HOMs). 49
4 - Conclusions The molecular interactions between sulfuric acid and methylamine have been investigated. Molecular geometries and formation free energies of (sa)1−4 (ma)1−4 clusters are reported. It is found that the clustering of sulfuric acid and methylamine is not capable of explaining observed new particle formation rates in the atmosphere, even when considering hydration in an ad hoc fashion. By comparing the energetics and new particle formation rates of the (sa)1−4 (ma)1−4 clusters to previously reported (sa)1−4 (dma)1−4 clusters it becomes apparent
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that the limiting step in sulfuric acid - base new particle formation is the formation of the initial (sa)1 (base)1 and (sa)2 (base)2 clusters. These findings further corroborate that strong bases are important chemical species in the initial formation of new particles in the atmosphere.
Acknowledgement J.E thanks the Villum foundation for financial support and the Danish e-Infrastructure Cooperation (DeIC) and CSC-IT Center for Science in Espoo, Finland, for computational resources.
Supporting Information Available The following is available as supporting information: • xyz-files of the studied molecular structures at the ωB97X-D/6-31++G(d,p) levels of theory. • All calculated Gibbs free energies. This material is available free of charge via the Internet at http://pubs.acs.org/.
References (1) WHO (World Health Organization), Public health, environmental and social determinants of health, 2014. (2) Haywood, J.; Boucher, O. Estimates of the Direct and Indirect Radiative Forcing due to Tropospheric Aerosols: A Review. Rev. Geophys. 2000, 38, 513–543. (3) Sipil¨a, M.; Berndt, T.; Pet¨aj¨a, T.; Brus, D.; Vanhanen, J.; Stratmann, F.; Patokoski, J.; Mauldin, R. L.; Hyvrinen, A.-P.; Lihavainen, H. et al. The Role of Sulfuric Acid in Atmospheric Nucleation. Science 2010, 327, 1243–1246. 17
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(4) Kulmala, M.; Vehkam¨aki, H.; Pet¨aj¨a, T.; Maso, M. D.; Lauri, A.; Kerminen, V.-M.; Birmili, W.; McMurry, P. Formation and Growth Rates of Ultrafine Atmospheric Particles: A Review of Observations. J. Aerosol Sci. 2004, 35, 143 – 176. (5) Kirkby, J.; Curtius, J.; Almeida, J.; Dunne, E.; Duplissy, J.; Ehrhart, S.; Franchin, A.; Gagne, S.; Ickes, L.; Krten, A. et al. Role of Sulphuric Acid, Ammonia and Galactic Cosmic Rays in Atmospheric Aerosol Nucleation. Nature 2011, 476, 429 – 433. (6) Weber, R. J.; Marti, J. J.; McMurry, P. H.; Eisele, F. L.; Tanner, D. J.; Jefferson, A. Measured Atmospheric New Particle Formation Rates: Implications for Nucleation Mechanisms. Chem. Eng. Comm. 1996, 151, 53–64. (7) Kurt´en, T.; Loukonen, V.; Vehkam¨aki, H.; Kulmala, M. Amines are Likely to Enhance Neutral and Ion-induced Sulfuric Acid-water Nucleation in the Atmosphere More Effectively than Ammonia. Atmos. Chem. Phys. 2008, 8, 4095–4103. (8) Nadykto, A. B.; Yu, F.; Jakovleva, M. V.; Herb, J.; Xu, Y. Amines in the Earth’s Atmosphere: A Density Functional Theory Study of the Thermochemistry of PreNucleation Clusters. Entropy 2011, 13, 554–569. (9) Nadykto, A. B.; Herb, J.; Yu, F.; Xu, Y. Enhancement in the Production of Nucleating Clusters due to Dimethylamine and Large Uncertainties in the Thermochemistry of Amine-Enhanced Nucleation. Chem. Phys. Lett. 2014, 609, 42–49. (10) DePalma, J. W.; Bzdek, B. R.; Doren, D. J.; Johnston, M. V. Structure and Energetics of Nanometer Size Clusters of Sulfuric Acid with Ammonia and Dimethylamine. J. Phys. Chem. A 2012, 116, 1030–1040. (11) DePalma, J. W.; Doren, D. J.; Johnston, M. V. Formation and Growth of Molecular Clusters Containing Sulfuric Acid, Water, Ammonia, and Dimethylamine. J. Phys. Chem. A 2014, 118, 5464–5473.
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(12) Almeida, J.; Schobesberger, S.; K¨ urten, A.; Ortega, I. K.; Kupiainen-M¨a¨att¨a, O.; Praplan, A. P.; Adamov, A.; Amorim, A.; Bianchi, F.; Breitenlechner, M. et al. Molecular Understanding of Sulphuric Acid-Amine Particle Nucleation in the Atmosphere. Nature 2013, 502, 359–363. (13) K¨ urten, A.; Jokinen, T.; Simon, M.; Sipil, M.; Sarnela, N.; Junninen, H.; Adamov, A.; Almeida, J.; Amorim, A.; Bianchi, F. et al. Neutral Molecular Cluster Formation of Sulfuric Acid-Dimethylamine Observed in Real Time under Atmospheric Conditions. Proc. Natl. Acad. Sci. U.S.A. 2014, 111, 15019–15024. (14) Jen, C. N.; McMurry, P. H.; Hanson, D. R. Stabilization of Sulfuric acid Dimers by Ammonia, Methylamine, Dimethylamine, and Trimethylamine. J Geophys. Res. Atmos. 2014, 119, 7502–7514. (15) Glasoe, W. A.; Volz, K.; Panta, B.; Freshour, N.; Bachman, R.; Hanson, D. R.; McMurry, P. H.; Jen, C. Sulfuric Acid Nucleation: An Experimental Study of the Effect of Seven Bases. J. Geophys. Res. Atmos. 2015, 120, 1933–1950. (16) Elm, J.; Jen, C. N.; Kurt´en, T.; Vehkam¨aki, H. Strong Hydrogen Bonded Molecular Interactions between Atmospheric Diamines and Sulfuric Acid. J. Phys. Chem. A 2016, 120, 3693–3700. (17) Jen, C. N.; Bachman, R.; Zhao, J.; McMurry, P. H.; Hanson, D. R. Diamine-Sulfuric Acid Reactions are a Potent Source of New Particle Formation. Geophys. Res. Lett. 2016, 43, 867–873. (18) Elm, J.; Passananti, M.; Kurt´en, T.; Vehkam¨aki, H. Diamines Can Initiate New Particle Formation in the Atmosphere. J. Phys. Chem. A 2017, 121, 6155–6164. (19) Nadykto, A. B.; Herb, J.; Yu, F.; Xu, Y.; Nazarenko, E. S. Estimating the Lower Limit of the Impact of Amines on Nucleation in the Earth’s Atmosphere. Entropy 2015, 17, 2764–2780. 19
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(20) Olenius, T.; Halonen, R.; Kurt´en, T.; Henschel, H.; Kupiainen-M¨aa¨tt¨a, O.; Ortega, I. K.; Jen, C. N.; Vehkam¨aki, H.; Riipinen, I. New Particle Formation From Sulfuric Acid and Amines: Comparison of Mono-, Di-, and Trimethylamines. J. Geophys. Res. Atmos 2017, 122, 7103–7118. (21) Ge, X.; Wexler, A. S.; Clegg, S. L. Atmospheric Amines - Part I. A Review. Atmos. Environ. 2011, 45, 524–546. (22) Gaussian 09, Revision D.01, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson, et al., Gaussian, Inc., Wallingford CT, 2013. (23) Elm, J.; Bilde, M.; Mikkelsen, K. V. Assessment of Binding Energies of Atmopsheric Clusters. Phys. Chem. Chem. Phys 2013, 15, 16442–16445. (24) Elm, J.; Kristensen, K. Basis Set Convergence of the Binding Energies of Strongly Hydrogen-Bonded Atmospheric Clusters. Phys. Chem. Chem. Phys 2017, 19, 1122– 1133. (25) Chai, J.; Martin, H. Long-Range Corrected Hybrid Density Functionals with Damped Atom-Atom Dispersion Corrections. Phys. Chem. Chem. Phys. 2008, 10, 6615–6620. (26) Elm, J.; Mikkelsen, K. V. Computational Approaches for Efficiently Modelling of Small Atmospheric Clusters. Chem. Phys. Lett. 2014, 615, 26–29. (27) Myllys, N.; Elm, J.; Kurt´en, T. Density Functional Theory Basis Set Convergence of Sulfuric Acid-Containing Molecular Clusters. Comp. Theor. Chem. 2016, 1098, 1–12. (28) Riplinger, C.; Neese, F. An Efficient and Near Linear Scaling Pair Natural Orbital Based Local Coupled Cluster Method. J. Chem. Phys. 2013, 138, 034106. (29) Riplinger, C.; Sandhoefer, B.; Hansen, A.; Neese, F. Natural Triple Excitations in Local
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Coupled Cluster Calculations with Pair Natural Orbitals. J. Chem. Phys. 2013, 139, 134101. (30) Neese F., WIREs Comput Mol Sci 2012, 2: 73-78 doi: 10.1002/wcms.81. (31) Myllys, N.; Olenius, T.; Kurt´en, T.; Vehkam¨aki, H.; Riipinen, I.; Elm, J. Effect of Bisulfate, Ammonia, and Ammonium on the Clustering of Organic Acids and Sulfuric Acid. J. Phys. Chem. A 2017, 121, 4812–4824. (32) Grimme, S. Supramolecular Binding Thermodynamics by Dispersion-corrected Density Functional Theory. Chem. Eur. J. 2012, 18, 9955–9964. (33) I.
Funes-Ardois,
R.
Paton,
GoodVibes:
GoodVibes
v1.0.1,
2016,
doi:http://dx.doi.org/10.5281/zenodo.60811. (34) Xie, H.; Elm, J.; Halonen, R.; Myllys, N.; Kurt´en, T.; Kulmala, M.; Vehkam¨aki, H. The Atmospheric Fate of Monoethanolamine: Enhancing New-particle Formation of Sulfuric Acid as an Important Removal Process. Environ. Sci. Technol. 2017, (35) McGrath, M. J.; Olenius, T.; Ortega, I. K.; Loukonen, V.; Paasonen, P.; Kurt´en, T.; Kulmala, M.; Vehkam¨aki, H. Atmospheric Cluster Dynamics Code: A Flexible Method for Solution of the Birth-Death Equations. Atmos. Chem. Phys. 2012, 12, 2345–2355. (36) Ortega, I. K.; Kupiainen, O.; Kurt´en, T.; Olenius, T.; Wilkman, O.; McGrath, M. J.; Loukonen, V.; Vehkam¨aki, H. From Quantum Chemical Formation Free Energies to Evaporation Rates. Atmos. Chem. Phys. 2012, 12, 225–235. (37) Olenius, T.; Kupiainen-M¨a¨att¨a, O.; Ortega, I. K.; Kurt´en, T.; Vehkam¨aki, H. Free Energy Barrier in the Growth of Sulfuric Acid-Ammonia and Sulfuric Acid-Dimethylamine Clusters. J. Chem. Phys. 2013, 139, doi: 10.1063/1.4819024. (38) Riccobono, F.; Schobesberger, S.; Scott, C. E.; Dommen, J.; Ortega, I. K.; Rondo, L.; Almeida, J.; Amorim, A.; Bianchi, F.; Breitenlechner, M. et al. Oxidation Products of 21
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Biogenic Emissions Contribute to Nucleation of Atmospheric Particles. Science 2014, 344, 717–721. (39) Kirkby, J.; Duplissy, J.; Sengupta, K.; Frege, C.; Gordon, H.; Williamson, C.; Heinritzi, M.; Simon, M.; Yan, C.; Almeida, J. et al. Ion-Induced Nucleation of Pure Biogenic Particles. Nature 2016, 533, 521–526. (40) Dal Maso, M.; Hyvrinen, A.; Komppula, M.; Tunved, P.; Kerminen, V.-M.; Lihavainen, H.; Viisanen, Y.; Hansson, H.-C.; Kulmala, M. Annual and Interannual Variation in Boreal Forest Aerosol Particle Number and Volume Concentration and their Connection to Particle Formation. Tellus B 2008, 60, 495–508. (41) Kontkanen, J.; Lehtipalo, K.; Ahonen, L.; Kangasluoma, J.; Manninen, H. E.; Hakala, J.; Rose, C.; Sellegri, K.; Xiao, S.; Wang, L. et al. Measurements of Sub-3 nm Particles using a Particle Size Magnifier in Different Environments: From Clean Mountain Top to Polluted Megacities. Atmos. Chem. Phys. 2017, 17, 2163–2187. (42) Bzdek, B. R.; DePalma, J. W.; Johnston, M. V. Mechanisms of Atmospherically Relevant Cluster Growth. Acc. Chem. Res. 2017, 50, 1965–1975. (43) Sihto, S.-L.; Kulmala, M.; Kerminen, V.-M.; Dal Maso, M.; Pet¨aj¨a, T.; Riipinen, I.; Korhonen, H.; Arnold, F.; Janson, R.; Boy, M. et al. Atmospheric Sulphuric Acid and Aerosol Formation: Implications from Atmospheric Measurements for Nucleation and Early Growth Mechanisms. Atmos. Chem. Phys. 2006, 6, 4079–4091. (44) Kuang, C.; McMurry, P. H.; McCormick, A. V.; Eisele, F. L. Dependence of Nucleation Rates on Sulfuric Acid Vapor Concentration in Diverse Atmospheric Locations. J. Geophys. Res. 2008, 113, D10209. (45) Paasonen, P.; Nieminen, T.; Asmi, E.; Manninen, H. E.; Pet¨aj¨a, T.; Plass-D¨ ulmer, C.; Flentje, H.; Birmili, W.; Wiedensohler, A.; H˜ orrak, U. et al. On the Roles of Sulphuric
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Acid and Low-volatility Organic Vapours in the Initial Steps of Atmospheric New Particle Formation. Atmos. Chem. Phys 2010, 10, 11223–11242. (46) Kupiainen-M¨aa¨tt¨a, O.; Olenius, T.; Korhonen, H.; Malila, J.; Dal Maso, M.; Lehtinen, K.; Vehkam¨aki, H. Critical Cluster Size Cannot in Practice Be Determined by Slope Analysis in Atmospherically Relevant Applications. J. Aerosol Sci. 2014, 77, 127–144. (47) Bustos, D. J.; Temelso, B.; Shields, G. C. Hydration of the Sulfuric Acid-Methylamine Complex and Implications for Aerosol Formation. J. Phys. Chem. A 2014, 118, 7430– 7441. (48) Henschel, H.; Kurt´en, T.; Vehkam¨aki, H. Computational Study on the Effect of Hydration on New Particle Formation in the Sulfuric Acid/Ammonia and Sulfuric Acid/ Dimethylamine Systems. J. Phys. Chem. A. 2016, 120, 1886–1896. (49) Kulmala, M.; Kontkanen, J.; Junninen, H.; Lehtipalo, K.; Manninen, H. E.; Nieminen, T.; Pet¨aj¨a, T.; Sipil¨a, M.; Schobesberger, S.; Rantala, P. et al. Direct Observations of Atmospheric Aerosol Nucleation. Science 2013, 339, 943–946.
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