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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Energetics of the nucleation and glide of disconnection modes in symmetric tilt grain boundaries

Grain boundaries (GBs) evolve by the nucleation and glide of disconnections, which are dislocations with a step character. In this work, motivated by recent success in predicting GB properties such as the shear coupling factor and mobility from the intrinsic properties of disconnections, we develop a systematic method to calculate the energy barriers for the nucleation and glide of individual disconnection modes under arbitrary driving forces and a quasi-2D setting. This method combines tools from bicrystallography to enumerate disconnection modes and the Nudged elastic band (NEB) method to calculate their energetics, yielding minimum energy paths and atomistic mechanisms for the nucleation and glide of each disconnection mode. We apply the method to accurately predict shear coupling factors of $[001]$ symmetric tilt grain boundaries in Cu. Particular attention is paid to the boundaries where the dislocation-based disconnection nucleation model produces incorrect nucleation barriers. We demonstrate that the method can accurately compute energy barriers and predict shear-coupling factors in the low-temperature regime. For certain disconnection modes in which the assumptions underlying our method do not hold, we report upper bounds on the energy barriers for disconnection nucleation and glide. In addition, the NEB trajectories reveal interesting phenomena such as the dissociation of a higher energy mode into lower energy modes, and in some cases, shear coupling being mediated by partial disconnections, wherein the GB structure temporarily changes to a metastable state before reverting back to its original structure. Graphical abstract

36 MATERIALS SCIENCE↗
DOE OSTI2013

Effect of nucleation time on bending response of ionic polymer–metal composite actuators

We attempted an autocatalytic electro-less plating of nickel in order to replace an electroless impregnation-reduction (IR) method in ionic polymer–metal composite (IPMC) actuators to reduce cost and processing time. Because nucleation time of Pd–Sn colloids is the determining factor of overall processing time, we used the nucleation time as our control parameter. In order to optimize nucleation time and investigate its effect on the performance of IPMC actuators, we analyzed the relationship between the nucleation time, interface morphology and electrical properties. The optimized nucleation time was 10 h. Furthermore, the trends of the performance and electrical properties as a function of nucleation time were attributed to the fact that the Ni penetration depth was determined by the minimum diffusion length of either Pd–Sn colloids or reducing agent ions. The Ni-IPMC actuators can be fabricated less than 14 h processing time without deteriorating performance of the actuators, which is comparable to Pt-IPMC prepared by IR method.

36 MATERIALS SCIENCE↗
DOE OSTI2017

From Aβ Filament to Fibril: Molecular Mechanism of Surface-Activated Secondary Nucleation from All-Atom MD Simulations

Secondary nucleation pathways in which existing amyloid fibrils catalyze the formation of new aggregates and neurotoxic oligomers are of immediate importance for the onset and progression of Alzheimer’s disease. Here, we apply extensive all-atom molecular dynamics simulations in explicit water to study surface-activated secondary nucleation pathways at the extended lateral β-sheet surface of a preformed Aβ9–40 filament. Calculation of free-energy profiles allows us to determine binding free energies and conformational intermediates for nucleation complexes consisting of 1–4 Aβ peptides. In addition, we combine the free-energy profiles with position-dependent diffusion profiles to extract complementary kinetic information and macroscopic growth rates. Single monomers bind to the β-sheet surface in a disordered, hydrophobically collapsed conformation, whereas dimers and larger oligomers can retain a cross-β conformation resembling a more ordered fibril structure. The association processes during secondary nucleation follow a dock/lock mechanism consisting of a fast initial encounter phase (docking) and a slow structural rearrangement phase (locking). The major driving forces for surface-activated secondary nucleation are the release of a large number of hydration water molecules and the formation of hydrophobic interface contacts, the latter being in contrast to the elongation process at filament tips, which is dominated by the formation of stable and highly specific interface hydrogen bonds. The calculated binding free energies and the association rates for the attachment of Aβ monomers and oligomers to the extended lateral β-sheet surface of the filament seed are higher compared to those for elongation at the filament tips, indicating that secondary nucleation pathways can become important once a critical concentration of filaments has formed.

Schwierz, Nadine↗
DOE OSTI2017

Homogeneous Nucleation of Ice in Transiently-Heated, Supercooled Liquid Water Films

e have investigated the nucleation and growth of crystalline ice in 0.24 µm thick, supercooled water films deposited on Pt(111) at cryogenic temperatures. The films were heated with ~10 ns infrared laser pulses, which produced typical heating and cooling rates of ~109 – 1010 K/s. The crystallization of these water films was monitored with infrared spectroscopy. The experimental conditions were chosen such that ice nucleation at the water/metal interface was suppressed and nucleation at the water/vacuum interfaces did not affect the observations. Since the water films were flat, their internal pressure was not raised due to curvature effects. Therefore, the experiments were sensitive to the homogeneous ice nucleation rate in the temperature range from ~210 K to 225 K. The experiments show that the maximum for the homogeneous ice nucleation rate versus temperature, Jmax, needs to be = 1026 m-3s-1 and is likely to be ~1029±2 m-3s-1. We argue that such large nucleation rates are consistent with experiments on hyperquenched glassy water, which typically have crystalline fractions of ~1% or more.

Xu, Yuntao↗
DOE OSTI2017

Regulating Multiple Variables To Understand the Nucleation and Growth and Transformation of PbS Nanocrystal Superlattices

Nanocrystals (NCs) can self-assemble into ordered superlattices with collective properties, but the ability for controlling NC assembly remains poorly understandable toward achievement of desired superlattice. This paper regulates several key variables of PbS NC assembly (e.g., NC concentration and solubility, solvent type, evaporation rate, seed mediation and thermal treatment), and thoroughly exploits the nucleation and growth as well as subsequent superlattice transformation of NC assembles and underneath mechanisms. PbS NCs in toluene self-assemble into a single face-centered-cubic (fcc) and body-centered-cubic (bcc) superlattice, respectively, at concentrations ≤17.5 and ≥70 mg/mL, but an intermediate concentration between them causes the coexistence of the two superlattices. Differently, NCs in hexane or chloroform self-assemble into only a single bcc superlattice. Distinct controls of NC assembly in solvent with variable concentrations confirm the NC concentration/solubility mediated nucleation and growth of superlattice, in which an evaporation-induced local gradient of NC concentration causes simultaneous nucleation of the two superlattices. The observation for the dense packing planes of NCs in fast growing fcc rather than bcc reveals the difference of entropic driving forces responsible for the two distinct superlattices. Decelerating the solvent evaporation does not amend the superlattice symmetry, but improves the superlattice crystallinity. In addition to shrinking the superlattice volume, thermal treatment also transforms the bcc to an fcc superlattice at 175 °C. Through a seed-meditated growth, the concentration-dependent superlattice does not change lattice symmetry over the course of continuous growth, whereas the newly nucleated secondary small nuclei through a concentration change have relatively higher surface energy and quickly dissolve in solution, providing additional NC sources for the ripening of the primarily nucleated larger and stable seeds. Finally, the observations under multiple controls of assembly parameters not only provide insights into the nucleation and growth as well as transformation of various superlattice polymorphs but also lay foundation for controlled fabrication of desired superlattice with tailored property.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

A marine biogenic source of atmospheric ice-nucleating particles

The formation of ice in clouds is facilitated by the presence of airborne ice nucleating particles1,2. Sea spray is one of the major global sources of atmospheric particles, but it is unclear to what extent these particles are capable of nucleating ice3–11. Here we show that material in the sea surface microlayer, which is enriched in surface active organic material representative of that found in sub-micron sea- spray aerosol12–21, nucleates ice under conditions that occur in mixed-phase clouds and high-altitude ice clouds. The ice active material is likely biogenic and is less than ~0.2 ?m in size. We also show that organic material (exudate) released by a common marine diatom nucleates ice when separated from cells and propose that organic material associated with phytoplankton cell exudates are a candidate for the observed ice nucleating ability of the microlayer samples. By combining our measurements with global model simulations of marine organic aerosol, we show that ice nucleating particles of marine origin are dominant in remote marine environments, such as the Southern Ocean, the North Pacific and the North Atlantic.

Wilson, T. W.↗
DOE OSTI2018

The role of confined collagen geometry in decreasing nucleation energy barriers to intrafibrillar mineralization

Mineralization of collagen is critical for the mechanical functions of bones and teeth. Calcium phosphate nucleation in collagenous structures follows distinctly different patterns in highly confined gap regions (nanoscale confinement) than in less confined extrafibrillar spaces (microscale confinement). Although the mechanism(s) driving these differences are still largely unknown, differences in the free energy for nucleation may explain these two mineralization behaviors. Here, we report on experimentally obtained nucleation energy barriers to intra- and extrafibrillar mineralization, using in situ X-ray scattering observations and classical nucleation theory. Polyaspartic acid, an extrafibrillar nucleation inhibitor, increases interfacial energies between nuclei and mineralization fluids. In contrast, the confined gap spaces inside collagen fibrils lower the energy barrier by reducing the reactive surface area of nuclei, decreasing the surface energy penalty. The confined gap geometry, therefore, guides the two-dimensional morphology and structure of bioapatite and changes the nucleation pathway by reducing the total energy barrier.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Communication: Nucleation rates of supersaturated aqueous NaCl using a polarizable force field

In this work, we use molecular dynamics simulations with a polarizable force field, namely, the modified AH/BK3 model [J. Kolafa, J. Chem. Phys. 145, 204509 (2016)], in combination with the forward flux sampling technique, to calculate the rates of homogeneous nucleation of NaCl from supersaturated aqueous solutions at 298 K and 1 bar. A non-polarizable model that reproduces the experimental equilibrium solubility {AH/TIP4P-2005 of Benavides et al. [J. Chem. Phys. 147, 104501 (2017)]} is also used for comparison. Nucleation rates calculated from the polarizable force field are found to be in good agreement with experimental measurements, while the non-polarizable model severely underestimates the nucleation rates. These results, in combination with our earlier study of a different non-polarizable force field [H. Jiang et al., J. Chem. Phys. 148, 044505 (2018)], lead to the conclusion that nucleation rates are sensitive to the details of force fields, and a good representation of nucleation rates may not be feasible using available non-polarizable force fields, even if these reproduce the equilibrium salt solubility. Finally, inclusion of polarization could be important for an accurate prediction of nucleation rates in salt solutions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Influence of surface chemistry on Li nucleation energetics on graphene-based surfaces

Lithium metal is a promising high-capacity anode material for solid-state batteries, but it typically suffers from poor cyclability. Carbon scaffold hosts have the potential to improve this performance due to their high electronic conductivity and large surface area, which facilitates lithium-ion adsorption and desorption. Scaffold surface chemistry is known to significantly influence performance outcomes, but the details of these interactions are not fully understood. Here, this study employs first-principles simulations to explore lithium transport and nucleation on graphene anodes with various surface chemistries. Using enhanced sampling techniques, ab initio molecular dynamics, and density functional theory calculations, we find that although surface chemistry has a minimal impact on lithium interfacial transport, it influences surface nucleation significantly. Both heteroatom dopants and intrinsic defects lower the nucleation barrier, creating a more favorable environment for lithium nucleation compared to pristine graphene. In addition, our results reveal a complex interplay between surface lithium concentration, lithium transport, and nucleation kinetics. These findings highlight the potential of surface modifications to precisely control nucleation processes on carbon-based anodes and provide design guidance for reducing dendrite formation and improving the cycle life of solid-state batteries.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Nucleation of spatiotemporal structures from defect turbulence in the two-dimensional complex Ginzburg-Landau equation

We numerically investigate nucleation processes in the transient dynamics of the two-dimensional complex Ginzburg--Landau equation towards its "frozen'' state with quasi-stationary spiral structures. We study the transition kinetics from either the defect turbulence regime or random initial configurations to the frozen state with a well-defined low density of quasi-stationary topological defects. Nucleation events of spiral structures are monitored using the characteristic length between the emerging shock fronts. We study two distinct situations, namely either when the system is quenched far away from the transition limit or near it. In the former deeply quenched case, the average nucleation time for different system sizes is measured over many independent realizations. We employ an extrapolation method as well as a phenomenological formula to account for and eliminate finite-size effects. The non-zero (dimensionless) barrier for the nucleation of single spiral droplets in the extrapolated infinite system size limit suggests that the transition to the frozen state is discontinuous. Here, we also investigate the nucleation of spirals for systems that are quenched close to but beyond the crossover limit, and of target waves which emerge if a specific spatial inhomogeneity is introduced. In either of these cases, we observe long, "fat'' tails in the distribution of nucleation times, which also supports a discontinuous transition scenario.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

Nonthermal ice nucleation observed at distorted contact lines of supercooled water drops

Ice nucleation is the crucial step for ice formation in atmospheric clouds and therefore underlies climatologically relevant precipitation and radiative properties. Some progress has been made in understanding the roles of temperature, supersaturation, and material properties, but an explanation for the efficient ice nucleation occurring when a particle contacts a supercooled water drop has been elusive for over half a century. Here, we explore ice nucleation initiated at constant temperature and observe that mechanical agitation induces freezing of supercooled water drops at distorted contact lines. Results show that symmetric motion of supercooled water on a vertically oscillating substrate does not freeze, no matter how we agitate it. However, when the moving contact line is distorted with the help of trace amounts of oil or inhomogeneous pinning on the substrate, freezing can occur at temperatures much higher than in a static droplet, equivalent to ~1010 increase in nucleation rate. Several possible mechanisms are proposed to explain the observations. One plausible explanation among them, decreased pressure due to interface curvature, is explored theoretically and compared with the observational results quasiquantitatively. Indeed, the observed freezing-temperature increase scales with contact line speed in a manner consistent with the pressure hypothesis. Whatever the mechanism, the experiments demonstrate a strong preference for ice nucleation at three-phase contact lines compared to the two-phase interface, and they also show that movement and distortion of the contact line are necessary contributions to stimulating the nucleation process.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Nucleation of stoichiometric compounds from liquid: Role of the kinetic factor

The nucleation rate depends on the free-energy barrier and the kinetic factor. While the role of the free energy barrier is a text-book subject, the importance of the kinetic factor is frequently underestimated. Here in this study, we applied the mean first-passage time method, to obtain the free-energy landscape and kinetic factor directly from the molecular dynamics (MD) simulations of the nucleation of the face-centered cubic (fcc) phase in the pure Ni and the B2 phases in the Ni 50 Al 50 and Cu 50 Zr 50 alloys. The obtained data show that while the free-energy barrier for nucleation is higher in pure Ni the nucleation rate is considerably lower in the Ni 50 Al 50 alloy. This result can be explained by the slow attachment kinetics in the N i 50 A l 50 alloy, which was related to the ordered nature of the B2 phase. Even smaller fraction of the antisite defects in the C u 50 Z r 50 alloy leads to such a slow attachment kinetics that the nucleation is never observed for this alloy in the course of the MD simulation. Finally, this is consistent with the experimental facts that the Cu 50 Zr 50 alloy is a good glass forming alloy and the Ni 50 Al 50 alloy is not. Thus the present study demonstrates that the atom attachment rate can be the critical factor that controls the nucleation process under certain conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Enhanced nucleation mechanism in ruthenium atomic layer deposition: Exploring surface termination and precursor ligand effects with RuCpEt(CO)2

Miniaturization of microelectronic devices necessitates atomic precision in manufacturing techniques, particularly in the deposition of thin films. Atomic layer deposition (ALD) is recognized for its precision in controlling film thickness and composition on intricate three-dimensional structures. This study focuses on the ALD nucleation and growth mechanisms of ruthenium (Ru), a metal that has significant future implications for microelectronics. Despite its advantages, the deposition of a high surface-free energy material like Ru on a low surface-free energy material such as an oxide often faces challenges of large nucleation delays and non-uniform growth. To address these challenges, we explored the effectiveness of organometallic surface pretreatments using trimethylaluminum (TMA) or diethylzinc (DEZ) to enhance Ru film nucleation and growth. Our study employed a less-studied Ru precursor, cyclopentadienylethyl(dicarbonyl)ruthenium [RuCpEt(CO)2], which demonstrated promising results in terms of reduced nucleation delay and increased film continuity. Ru ALD was performed on silicon substrates with native oxide, using RuCpEt(CO)2 and O2 as coreactants. Our findings reveal that surface pretreatment significantly improves nucleation density and film thickness within the initial 60 ALD cycles, achieving up to a 3.2-fold increase in Ru surface coverage compared to nonpretreated substrates. Supported by density functional theory calculations, we propose that the enhanced nucleation observed with RuCpEt(CO)2 compared to previously-studied Ru(Cp)2 is due to two key mechanisms: the facilitated removal of CO ligands during deposition, which enhances the reactivity of the precursor, and a hydrogen-abstraction reaction involving the ethyl ligand of RuCpEt(CO)2 and the metal-alkyl groups on the surface. This study not only advances our understanding of Ru ALD processes but also highlights the significant impact of precursor chemistry and surface treatments in optimizing ALD for advanced microelectronic applications.

Materials Science↗
DOE OSTI2019

Ice nucleation ability of loess from the northwestern United States

The heterogeneous nucleation of ice processes involving loess particles that influences the formation of mixed-phase clouds are poorly understood. Here, the ice nucleating ability of wind-blown dust or loess accumulated from the past glaciated area was investigated at three temperatures: -26, -30, and -34 °C and at below and above saturation with respect to liquid water conditions. Total six loess samples from different regions across Columbia Basin province, WA, USA were collected, dry dispersed, size-selected at mobility diameter 200 nm, and investigated for their ice nucleation efficiency. To understand the effect of atmospheric processing during long-range transport on their ice nucleating ability, similar experiments were also performed on acid-treated loess samples. Additionally, the ice nucleating properties of Arizona Test Dust (ATD) were investigated as a surrogate for natural mineral dust particles to test the experimental approach. Results show that treated particles have lower ice nucleation efficiency compared to untreated particles at all temperature and saturation with respect to liquid water conditions. Comparison based on ice-active site density ( N s ) metric indicate that loess particles at saturation with respect to liquid water conditions are marginally more efficient than the mineral and soil dust values reported in the literature, but they have lower efficiencies than the predicted N s efficiency of K-feldspar particles at supercooled temperatures greater than -38 °C.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

International Workshop on Comparing Ice Nucleation Measuring Systems 2014

The relationship of ambient aerosol particles to the formation of ice-containing clouds is one of the largest uncertainties in understanding the Earth’s climate. The uncertainty is due to several poorly understood processes and measurements including, but not limited to: (1) the microphysics of how particles nucleate ice, (2) the number of ice forming particles as a function of atmospheric properties such as temperature and relative humidity, (3) the atmospheric distribution of ice forming particles and (4) the role of anthropogenic activities in producing or changing the behavior of ice forming particles. The ways in which ice forming particles can impact climate is also multi-faceted. More ice forming particles can lead to clouds with more ice crystals and different optical properties than clouds with less ice forming particles. More effective ice forming particles can lead to ice at higher temperature and/or lower saturation, resulting in clouds at lower altitude or latitude which also changes the Earth’s radiative balance. Ice nucleation also initiates most of the Earth’s precipitation, even in the mid- and low-latitudes, since cloud-top temperatures are often below freezing. The limited measurements and lack of understanding directly translates to restrictions in our ability to model atmospheric ice formation and project changes into the future. The importance of ice nucleation research is further exemplified by Figure 1 which shows the publications per decade and citations per year on the topic of ice nucleation [DeMott et al., 2011]. After a lull at the end of the last century, there has been a dramatic increase in both publications and citations related to ice nucleation; this directly corresponds to the importance of ice nucleation on the Earth’s climate and the uncertainty in this area noted by the Solomon [2007].

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Integrating laboratory and field data to quantify the immersion freezing ice nucleation activity of mineral dust particles

Data from both laboratory studies and atmospheric measurements are used to develop an empirical parameterization for the immersion freezing activity of natural mineral dust particles. Measurements made with the Colorado State University (CSU) continuous flow diffusion chamber (CFDC) when processing mineral dust aerosols at a nominal 105% relative humidity with respect to water (RH w ) are taken as a measure of the immersion freezing nucleation activity of particles. Ice active frozen fractions vs. temperature for dusts representative of Saharan and Asian desert sources were consistent with similar measurements in atmospheric dust plumes for a limited set of comparisons available. The parameterization developed follows the form of one suggested previously for atmospheric particles of non-specific composition in quantifying ice nucleating particle concentrations as functions of temperature and the total number concentration of particles larger than 0.5 μm diameter. Such an approach does not explicitly account for surface area and time dependencies for ice nucleation, but sufficiently encapsulates the activation properties for potential use in regional and global modeling simulations, and possible application in developing remote sensing retrievals for ice nucleating particles. A calibration factor is introduced to account for the apparent underestimate (by approximately 3, on average) of the immersion freezing fraction of mineral dust particles for CSU CFDC data processed at an RH w of 105% vs. maximum fractions active at higher RH w . Instrumental factors that affect activation behavior vs. RH w in CFDC instruments remain to be fully explored in future studies. Nevertheless, the use of this calibration factor is supported by comparison to ice activation data obtained for the same aerosols from Aerosol Interactions and Dynamics of the Atmosphere (AIDA) expansion chamber cloud parcel experiments. Further comparison of the new parameterization, including calibration correction, to predictions of the immersion freezing surface active site density parameterization for mineral dust particles, developed separately from AIDA experimental data alone, shows excellent agreement for data collected in a descent through a Saharan aerosol layer. These studies support the utility of laboratory measurements to obtain atmospherically relevant data on the ice nucleation properties of dust and other particle types, and suggest the suitability of considering all mineral dust as a single type of ice nucleating particle as a useful first-order approximation in numerical modeling investigations.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Production of ice-nucleating particles (INPs) by fast-growing phytoplankton

Sea spray aerosol contains ice-nucleating particles (INPs), which affect the formation and proper ties of clouds. Here, we show that aerosols emitted from fast-growing marine phytoplankton produce effective immersion INPs, which nucleate at temperatures significantly warmer than the atmospheric homogeneous freezing (-38.0 °C) of pure water. Aerosol sampled over phytoplankton cultures grown in a Marine Aerosol Ref erence Tank (MART) induced nucleation and freezing at temperatures as high as -15.0 °C during exponential phytoplankton growth. This was observed in monospecific cultures representative of two major groups of phy toplankton, namely a cyanobacterium (Synechococcus elongatus) and a diatom (Thalassiosira weissflogii). Ice nucleation occurred at colder temperatures (-28.5 °C and below), which were not different from the freezing temperatures of procedural blanks, when the cultures were in the stationary or death phases of growth. Ice nucleation at warmer temperatures was associated with relatively high values of the maximum quantum yield of photosystem II ( Φ PSII ), an indicator of the physiological status of phytoplankton. High values of Φ PSII indicate the presence of cells with efficient photochemistry and greater potential for photosynthesis. For comparison, field measurements in the North Atlantic Ocean showed that high net growth rates of natural phytoplankton assemblages were associated with marine aerosol that acted as effective immersion INPs at relatively warm temperatures. Data were collected over 4 d at a sampling station maintained in the same water mass as the water column stabilized after deep mixing by a storm. Phytoplankton biomass and net phytoplankton growth rate (0.56 d -1 ) were greatest over the 24 h preceding the warmest mean ice nucleation temperature (-25.5 °C). Collectively, our laboratory and field observations indicate that phytoplankton physiological status is a useful predictor of effective INPs and more reliable than biomass or taxonomic affiliation. Ocean regions associated with fast phytoplankton growth, such as the North Atlantic during the annual spring bloom, may be significant sources of atmospheric INPs.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

A dynamic parameterization of sulfuric acid–dimethylamine nucleation and its application in three-dimensional modeling

Sulfuric acid (SA) is a governing gaseous precursor for atmospheric new particle formation (NPF), a major source of global ultrafine particles, in environments studied around the world. In polluted urban atmospheres with high condensation sinks (CSs), the formation of stable SA–amine clusters, such as SA–dimethylamine (DMA) clusters, usually initializes intense NPF events. Coagulation scavenging and cluster evaporation are dominant sink processes of SA–amine clusters in urban atmospheres, yet these loss processes are not quantitatively included in the present parameterizations of SA–amine nucleation. We herein report a parameterization of SA–DMA nucleation, based on cluster dynamic simulations and quantum chemistry calculations, with certain simplifications to greatly reduce the computational costs. Compared with previous SA–DMA nucleation parameterizations, this new parameterization was able to reproduce the dependences of particle formation rates on temperature and CSs. We then incorporated it in a three-dimensional (3-D) chemical transport model to simulate the evolution of the particle number size distributions. Simulation results showed good consistency with the observations in the occurrence of NPF events and particle number size distributions in wintertime Beijing and represented a significant improvement compared to that using a parameterization without coagulation scavenging. Quantitative analysis shows that SA–DMA nucleation contributes significantly to nucleation rates and aerosol population during the 3-D simulations in Beijing (>99 % and >60 %, respectively). These results broaden the understanding of NPF in urban atmospheres and stress the necessity of including the effects of coagulation scavenging and cluster stability in simulating SA–DMA nucleation in 3-D simulations. Representing these processes is thus likely to improve model performance in particle source apportionment and quantification of aerosol effects on air quality, human health, and climate.

Li, Yuyang↗