Cluster Growth Process Research Articles

Resistance of a PdAu12(8e) Core to Growth in Collision-Induced Sequential Reductive Elimination of (C≡CR)2 from [PdAu24(C≡CR)18]2.

Previous studies have reported that [PdAu24(PAF)18]2- (PAF = 3,5-(CF3)2C6H3C≡C) with an icosahedral superatomic PdAu12(8e) core underwent collision-induced sequential reductive elimination (CISRE) of 1,3-diyne (PAF)2 ( J. Phys. Chem. C 2020, 124, 19119). The most likely scenario after the CISRE of (PAF)2 is the growth of the PdAu12(8e) core via the fusion of the Au(0) atoms produced from the Au2(PAF)3 units on the core surface. Contrary to expectation, anion photoelectron spectroscopy and theoretical calculations regarding the CISRE products [PdAu24(PAF)18-2n]2- (n = 1-6) revealed that the electronically closed PdAu12(8e) core does not grow to a single superatom with (8 + 2n)e but assembles with Au2(2e) units. Characterization of the CISRE products of other alkynyl-protected Au clusters suggested that even the non-superatomic Au17(8e) core was resistant to growth due probably to rigidification by PA ligands. We propose that there is a kinetic bottleneck in the growth process of protected Au clusters at the stage where they are electronically closed and/or lose their structural fluxionality by ligation.

Molecular dynamics simulation study of graphene synthesis by rotating arc plasma

The rotating arc plasma method, based on its unique characteristics, provides a simple, efficient, and catalyst-free approach for graphene material synthesis. This study employs molecular dynamics simulations to theoretically investigate the detailed growth process of graphene at the atomic scale using plasma. During the growth process, different radicals serve as dissociation precursors within the plasma. Simulation results indicate that the growth process of graphene clusters involves three stages: extension of carbon clusters, cyclization of carbon chains, and coalescence of clusters into sheets. Firstly, the precursor concentration affects the size of graphene clusters; increasing the precursor concentration enlarges the cluster size but also increases the likelihood of curling. Secondly, increasing the hydrogen content in the precursor can reduce the growth rate of clusters, decrease dangling bonds at the periphery of clusters, thereby slowing down cluster closure and maintaining a well-defined sheet structure. Lastly, appropriately elevating the simulation temperature can enhance the reaction rate during the simulation process without altering the reaction pathway. These research findings establish the foundation for understanding the growth mechanism of graphene.

Element-specific cluster growth on the two-dimensional metal–organic network

A porous two-dimensional metal–organic network (2D-MON) on a substrate captures deposited metal atoms and metal clusters growing in the pores of the 2D-MON. We found that the growth mechanisms of Ag, In, and Pd clusters in the 2D-MON synthesized from 1,3,5-tris(4-bromophenyl)benzene molecules on Ag(111) are different from each other, and the difference derives from the interaction of an adatom with the 2D-MON. Ag and Pd clusters grow from the 2D-MON since the interaction of Ag and Pd adatoms with the 2D-MON is attractive. In clusters grow inside of the pores of the 2D-MON since the interaction between an In adatom and the 2D-MON is repulsive. The growth process of metal clusters is determined by the element-specific behavior of metal adatoms in the pores, taking into account interactions with the 2D-MON.

Understanding the Formation and Growth of New Atmospheric Particles at the Molecular Level through Laboratory Molecular Beam Experiments.

Atmospheric new particle formation (NPF), which exerts comprehensive implications for climate, air quality and human health, has received extensive attention. From molecule to cluster is the initial and most important stage of the nucleation process of atmospheric new particles. However, due to the complexity of the nucleation process and limitations of experimental characterization techniques, there is still a great uncertainty in understanding the nucleation mechanism at the molecular level. Laboratory-based molecular beam methods can experimentally implement the generation and growth of typical atmospheric gas-phase nucleation precursors to nanoscale clusters, characterize the key physical and chemical properties of clusters such as structure and composition, and obtain a series of their physicochemical parameters, including association rate coefficients, electron binding energy, pickup cross section and pickup probability and so on. These parameters can quantitatively illustrate the physicochemical properties of the cluster, and evaluate the effect of different gas phase nucleation precursors on the formation and growth of atmospheric new particles. We review the present literatures on atmospheric cluster formation and reaction employing the experimental method of laboratory molecular beam. The experimental apparatuses were classified and summarized from three aspects of cluster generation, growth and detection processes. Focus of this review is on the properties of nucleation clusters involving different precursor molecules of water, sulfuric acid, nitric acid and NxOy, respectively. We hope this review will provide a deep insight for effects of cluster physicochemical properties on nucleation, and reveal the formation and growth mechanism of atmospheric new particle at the molecular level.

All-Hydrocarbon-Ligated Superatomic Gold/Aluminum Clusters.

Key strategies in cluster synthesis include the use of modulating agents (e.g., coordinating additives). We studied the influence of various phosphines exhibiting different steric and electronic properties on the reduction of the Au(I) precursor to Au(0) clusters. We report a synthesis of the bimetallic clusters [Au6(AlCp*)6] = [Au6Al6](Cp*)6 (1) and [HAu7(AlCp*)6] = [HAu7Al6](Cp*)6 (2) (Cp* = pentamethylcyclopentadiene) using Au(I) precursors and AlCp*. The cluster [Au2(AlCp*)5] = [Au2Al5](Cp*)5 (3) was isolated and identified as an intermediate species in the reactions to 1 and 2. The processes of cluster growth and degradation were investigated by in situ 1H NMR and LIFDI-MS techniques. The structures of 1 and 2 were established by DFT geometry optimization. These octahedral clusters can both be described as closed-shell 18-electron superatoms.

Growth mechanism prediction for nanoparticles via structure matching polymerization.

Exploring structural and component evolution remains a challenging scientific problem for nanoscience. We propose a novel approach called principle of minimization of structure matching polymerization (SMP) change to rapidly explore the global minimum structure on the potential energy surface (PES). The new method can map low-dimensional stable structures to high-dimensional local minima, and this will make it possible for us to study the growth mechanisms of nanoparticles. Some new lowest-energy structures were found by SMP methods for sulfuric acid (SA)-dimethylamine (DMA) systems relative to previous studies. Additionally, we found that the growth process of boron clusters is mainly that the small-size boron clusters are continuously added to large-size boron clusters by structure matching for Bn (n = 2-36) systems, Bm + Bk → Bn, where m + k = n and 1 ≤ k ≤ 3. The SMP approach can greatly improve the search efficiency of other unbiased global optimization algorithms, such as basin-hopping (BH) and genetic algorithm (GA), with an enhancement of up to 19- and 7-fold relative to traditional BH and GA algorithms for searching the global minima of Bn (n = 14-22) systems. The SMP approach is general and flexible and can be applied to different kinds of problems, such as material structure design, crystal structure prediction, and new drug generation.

Effects of size and temperature on the configurations of the Re-Ni clusters

The diffusion and growth dynamic processes of Re adatoms on a Wulff Ni substrate were simulated by combining molecular dynamics and embedded atom method. The configurations of the Re adatoms on Wulff1289 clusters at 100, 200, 300, and 600 K at different growth stages were compared. Results show that the optimal core-shell configurations were achieved at 100 K. The factors of substrate size (201, 586 and 1289 atoms) on cluster growth processes were analyzed. The quality of core-shell clusters obtained at different temperatures and sizes varies. The optimal quality of core-shell structure of Re adatoms growing on wulff586 Ni cluster was obtained at 200 K, while the corresponding temperature for Wulff201 Ni cluster was at 100 K. These findings indicate that optimal core-shell clusters can be obtained within our study’s size range at low temperatures, and the cluster size and temperature should be fully considered when designing the cluster configuration.

Making Sense of the Growth Behavior of Ultra-High Magnetic Gd2-Doped Silicon Clusters

The growth behavior, stability, electronic and magnetic properties of the Gd2Sin− (n = 3–12) clusters are reported, which are investigated using density functional theory calculations combined with the Saunders ‘Kick’ and the Artificial Bee Colony algorithm. The lowest-lying structures of Gd2Sin− (n = 3–12) are all exohedral structures with two Gd atoms face-capping the Sin frameworks. Results show that the pentagonal bipyramid (PB) shape is the basic framework for the nascent growth process of the present clusters, and forming the PB structure begins with n = 5. The Gd2Si5− is the potential magic cluster due to significantly higher average binding energies and second order difference energies, which can also be further verified by localized orbital locator and adaptive natural density partitioning methods. Moreover, the localized f-electron can be observed by natural atomic orbital analysis, implying that these electrons are not affected by the pure silicon atoms and scarcely participate in bonding. Hence, the implantation of these elements into a silicon substrate could present a potential alternative strategy for designing and synthesizing rare earth magnetic silicon-based materials.

Growth process of clusters formed by paramagnetic microparticles in an ac/dc combined magnetic field

Patterns formed by nano/microparticles in colloidal systems are of great interest and importance from both scientific and technological points of view. Magnetic colloids are particularly interesting since the structures formed by magnetic particles can be quite easily controlled by external magnetic fields. In this study, we investigate the growth process of clusters formed by paramagnetic microparticles in a fluctuating magnetic field composed of a direct current field applied in the vertical direction and an alternating current one in the horizontal direction. We find that thin walls, the thickness of which is equal to the diameter of a particle, are formed by paramagnetic particles; the horizontal length of the walls increases via wall-edge-to-wall-edge coagulation, but they do not grow laterally due to repulsive forces acting between walls in the lateral direction. Finally, we investigate the scaling features of the growth process of the walls. We find that a scaling law applies to the growth of the walls during a certain period of the growth process.

Electrochemical Nucleation and Growth of Cobalt after Leaching Waste Lithium-Ion Batteries Using a Deep Eutectic Solvent

The present work deals with the nucleation and growth process of metallic cobalt clusters onto glassy carbon, and the development of an environmentally friendly recycling process for the recovery of cobalt as a value-added product from spent lithium-ion batteries (LiBs), using a deep eutectic solvent, DES, formed by choline chloride and urea, termed reline. It was shown that reline works as leaching medium to extract Co(II) from cathode powders of dismantled spent batteries, thereby obtaining, after doing the electrodeposition process using the same reline as operating bath, a solid Co metal phase onto a glassy carbon electrode. Finally, supplementary relevant characterization of the deposits formed was carried out by means of scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-rays photoelectrons spectroscopy, XPS.

Structural evolution, electronic properties and spectra of titanium clusters

The ground-state structures, electronic properties and spectra of Ti n c ( n = 3–16 and c = 0, ±1) clusters have been investigated based on density functional theory (DFT) and CALYPSO structure prediction. Geometry optimizations show that the neutral, cationic and anionic titanium clusters have the same growth pattern. The pentagonal bipyramid plays an important role in the growth process. Analysis of electronic properties shows that the thermal stability of cationic and anionic clusters is greater than that of neutral cluster. The pentagonal bipyramid and icosahedron clusters have relatively high stability. Chemical activity of titanium clusters decreases with the cluster size. The preferred dissociation pathway of Ti n + clusters is the loss of a single Ti atom to form Ti n − 1 + . Optical absorption of Ti n clusters and infrared and Raman spectra of Ti n + clusters have been simulated and can be used for their structural identification. The ground states of Ti n − clusters have been determined by comparing experimental and theoretical photoelectron spectra. • The pentagonal bipyramid plays an important role in the growth process of titanium clusters • The titanium cluster with pentagonal bipyramid or icosahedron geometry is more table than other clusters. • The preferred dissociation pathway of Ti n + clusters is the loss of a single Ti atom to form Ti n − 1 + . • The ground state of anionic Ti n − clusters are identified by photoelectron spectra.s

Investigation on the growth characteristics of condensed droplet clusters on superhydrophobic surface within humid air

The dropwise condensation with supercooling is usually one of the processes of frosting on superhydrophobic surfaces within humid air. Investigation on the growth characteristics of droplet clusters before freezing helps to reveal the frost suppression mechanism of superhydrophobic surfaces and provides theoretical support for development of new defrosting methods. For the growth process of droplet clusters, the growth, deformation and jumping models of droplets are established, and the dynamic simulation algorithm for the clusters’ growth is developed. The models and simulations are verified through visual experiments. On that basis, the influencing mechanism of surface wettability, air humidity, substrate temperature on droplet growth and coalescence behavior is studied, and the growth of droplet clusters under typical frosting conditions is simulated. The results show that the growth rate of an individual droplet shows lower sensibility to substrate wettability and temperature compared with humidity, but the substrate wettability affects the coalescence behavior and then has a significant influence on the evolution of cluster parameters. The characteristic size of droplet clusters oscillates for the occurrence of jumping and regrowth in the condensation, and tends to be stable in the process approaching to equilibrium state.

Water migration through fat-based semi solid heterogeneous materials

• Water migration through fat-based composites is mediated by percolation process. • Permeating water network is provided by hydrophilic inclusions. • Size of percolating water cluster diverges with percolation exponent. • Water bridges between hydrophilic inclusions lead to mechanical stiffening. • Percolating moisture network enhances water loss in the heterogeneous material. Water migration through heterogeneous soft materials is central to many applications including oil recovery and consumer product stability of foods and cosmetics. This slow water transport affects all material properties such as mechanical, optical and electrical, but its understanding and modelling remains challenging due to complex wetting and diffusion processes across the heterogeneous material. Here, we study experimentally the penetration of water through a soft composite with hydrophobic (fat) and hydrophilic (salt) components. Conductivity measurements indicate the emergence of a percolating water network above critical water and salt volume fractions. This is corroborated by mechanical measurements revealing a concomitant stiffening of the material due to proliferating water bridges. Simulations of water absorption at spherical inclusions confirm this scenario and show the underlying cluster growth and percolation process.

Density functional theory study of solute cluster growth processes in Mg-Y-Zn LPSO alloys

Solute clusters in long period stacking order (LPSO) alloys play a key role in their idiosyncratic plastic behavior, for example kink formation and kink strengthening. Identifying atomistic details of cluster structures is a prerequisite for atomistic modeling of LPSO alloys and is crucial for improving their strength and ductility; however, there is much uncertainty regarding interstitial atoms in the cluster. Although density functional theory calculations have shown that the inclusion of Mg interstitial atoms is energetically most favorable in majority of LPSO alloys, solute elements have also been experimentally observed at interstitial sites. To predict the distributions of interstitial atoms in the cluster and to determine the kind of elements present, it is necessary to identify mechanisms by which interstitial atoms are created. In the present work, we use density functional theory calculations to investigate growth processes of solute clusters, specifically the Mg-Y-Zn LPSO alloy, in order to determine the precise atomistic structure of its solute clusters. We show that a pair of an interstitial atom and a vacancy are spontaneously created when a certain number of solute atoms are absorbed into the cluster, and that all full-grown clusters should include interstitial atoms. We also demonstrate that interstitial atoms are mostly Mg, while the rest are Y; interstitial Zn atoms are negligible. This knowledge greatly simplifies the atomistic modeling of solute clusters in Mg-Y-Zn alloys. Owing to the vacancies emitted from the cluster, vacancy density should be super-saturated in regions where solute clusters are growing, and increased vacancy density accelerates cluster growth.

Density Functional Theory Study of Solute Cluster Growth Process in Mg-Y-Zn Lpso Alloy

Solute cluster in LPSO alloys plays a key role in their idiosyncratic plastic behaviour such as kink formation and kink strengthening. Identifying atomistic details of the cluster structure is a prerequisite for any atomistic modeling of LPSO alloys aiming for their improved strength and ductility, but there have been uncertainty about interstitial atom in the cluster. While density functional theory calculations have shown that inclusion of interstitial atom is energetically favorable, it has been unclear how the extra atom is provided, how much of the cluster have interstitial atoms, and what kind of element they are. In the present work we use density functional theory calculations to investigate the growth process of the solute cluster, specifically that of Mg-Y-Zn LPSO alloy, to determine the precise atomistic structure of solute cluster. We show that a pair of an interstitial atom and a vacancy is spontaneously created when a certain number of solute atoms are absorbed into the cluster, and all the full-grown cluster should include interstitial atom. We also show that interstitial atoms are mostly Mg atoms, and the rest are Y atom, while Zn interstitial atoms are negligible. This knowledge greatly simplifies atomistic modeling of solute clusters in Mg-Y-Zn alloy. Owing to the vacancies emitted from the cluster, vacancy density should be over-saturated in regions where solute clusters are growing, and the increased vacancy density accelerates cluster growth.

Nonequilibrium master kinetic equation modeling of colloidal gelation.

We present a detailed study of the kinetic cluster growth process during gelation of weakly attractive colloidal particles by means of experiments on critical Casimir attractive colloidal systems, simulations, and analytical theory. In the experiments and simulations, we follow the mean coordination number of the particles during the growth of clusters to identify an attractive-strength independent cluster evolution as a function of mean coordination number. We relate this cluster evolution to the kinetic attachment and detachment rates of particles and particle clusters. We find that single-particle detachment dominates in the relevant weak attractive-strength regime, while association rates are almost independent of the cluster size. Using the limit of single-particle dissociation and size-independent association rates, we solve the master kinetic equation of cluster growth analytically to predict power-law cluster mass distributions with exponents -3/2 and -5/2 before and after gelation, respectively, which are consistent with the experimental and simulation data. These results suggest that the observed critical Casimir-induced gelation is a second-order nonequilibrium phase transition (with broken detailed balance). Consistent with this scenario, the size of the largest cluster is observed to diverge with power-law exponent according to three-dimensional percolation on approaching the critical mean coordination number.

Volatile organic compounds enhancing sulfuric acid-based ternary homogeneous nucleation: The important role of synergistic effect

Abstract New particle formation (NPF) is an important source of atmospheric aerosols. Sulfuric acid (SA) and water (W) are recognized as essential participating substances in the nucleation of the atmosphere. In addition, as one of the most common organic acids, oxalic acid (OA) can improve NPF when amine such as methylamine (MA) is present. However, exploring the properties of atmospheric particles made up of different components is challenging and the role of volatile organic compounds in SA–based ternary homogeneous nucleation is still lacking in research. In this work, the structures and energies of (SA)x(OA)y(MA)z(W)m (0 ≤ x, y, z ≤ 3, 0 ≤ m ≤ 1) are investigated. The results indicate that it is accessible for SA to form clusters with OA and MA molecules through hydrogen bonds and proton transfer interactions. The analysis of non–covalent interactions and proton transfer reveals that ternary nucleation systems have stronger hydrogen bonds and more proton transfers than binary systems to stabilize the clusters. In terms of the thermodynamic properties, the Gibbs free energies of the clusters will decrease as the addition of SA, OA or MA molecules indicating that the synergistic effect of these three substances may be of potential in forming the initial cluster and subsequent growth processes. Moreover, the evaporation rates of clusters show that the synergistic effect of ternary clusters leads to a decrease in evaporation rate which may promote atmospheric nucleation.

Continuous preparation and formation mechanism of few-layer graphene by gliding arc plasma

Environmental-friendly, rapid, and continuous preparation process of few-layer graphene has been developed by alternative-current (AC) rotating gliding arc plasma, which contains the characteristics of equilibrium plasma and non-equilibrium plasma. In the process, methane was directly cracked in the plasma and then graphene sheets were generated. The effects of hydrogen and gas flow rate on the yield, size, morphology and structure of graphene have been investigated. In addition, the formation mechanism of graphene was also revealed by using the reactive molecular dynamic method. The simulation results showed that the growth process of graphene clusters by methane radicals includes three stages: elongation of the carbon chains, cyclization of the carbon chains, and condensation and sheeting of clusters. The carbon source concentration influences the graphene clusters. Increasing the carbon source concentration was found to enlarge the size of graphene clusters but are more prone to curling and closing. The formation of C–H bonds can reduce the peripheral dangling bonds of the clusters, thereby delaying the closure of the clusters. It laid a foundation for understanding the growth mechanism of graphene.

Analysis of Cluster Growth in Magnetron-sputtering Metal-cluster Source by Optical Emission Spectroscopy

We investigate cluster-growth processes in a magnetron-sputtering cluster source by employing silver as a target metal. An optical emission spectrum of discharge plasma is measured along with a mas...

Molecular dynamics simulation on agglomeration and growth behavior of dust particles during flue gas filtration

High efficiency purification of dust particles contained in industrial flue gas is urgently needed to mitigate environmental pollution and improve waste heat recovery efficiency. The agglomeration and growth behavior of dust particles has significant effects on filtration efficiency of industrial flue gas. In this paper, in order to reveal the microscopic mechanism of dust particles agglomeration and growth, three kinds of typical components in industrial flue gas, such as steam (H2O), PAHs (naphthalene) and dust particles (SiO2) were selected to establish a molecular dynamics (MD) simulation system. The agglomeration behavior of dust particles and the formation and growth process of dust clusters were characterized by MD simulation. The effects of temperature, channel width, cooling rate and gas composition on the agglomeration behavior of dust particles and the growth of dust clusters were investigated. It is found that the formation and growth of dust clusters are driven by agglomeration of dust particles. The decrease of gas temperature, cooling rate and channel width can accelerate the agglomeration of dust particles and the growth of dust clusters, which is beneficial to dust particles filtration. In addition, the hydrogen bonds formed between the H2O molecules and SiO2 particles can promote the adsorption of SiO2 particles to the H2O molecules, which is also beneficial to the formation and growth of dust clusters. So increasing the content of steam in industrial flue gas is helpful to the growth of dust clusters and the filtration of dust particles.