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Although impurities are unavoidable in real-world and experimental systems, most numerical studies on nucleation focus on pure (impurity-free) systems. As a result, the role of impurities in phase transitions remains poorly understood, especially for systems with complex free energy landscapes featuring one or more intermediate metastable phases. In this study, we employed Monte Carlo simulations to investigate the effects of static impurities (quenched disorder) of varying length scales and surface morphologies on the crystal nucleation mechanism and kinetics in the Gaussian core model system—a representative model for soft colloidal systems. We first explored how the nucleation free energy barrier and critical cluster size are influenced by the fraction of randomly pinned (or, static) particles (fp) and the size (np) of the pinned region or cluster. Both the nucleation free energy barrier and critical cluster size increase sharply with increasing fp but decrease as np grows for a given fraction of pinned particles, eventually approaching the homogeneous nucleation limit. On examining the impact of impurity's surface morphology on nucleation kinetics, we observed that the nucleation barrier significantly decreases with increasing the impurity (or, seed) size with crystalline surface morphologies with body-centered cubic showing the greatest facilitation. Interestingly, seeds with random surface roughness had little effect on nucleation kinetics. In addition, the polymorphic identity of particles in the final crystalline phase is influenced by both the seed's surface morphology and system size. This study further provides crucial insights into the intricate relationship between surface-induced local structural fluctuations and the selection of the polymorphic identity in the final crystalline phase, which is essential for understanding and controlling crystallization processes in experiments. [ABSTRACT FROM AUTHOR]

We conducted homogeneous nucleation experiments for dilute binary H2O–CO2 mixtures in Ar–N2 carrier gas with different CO2/H2O ratios at temperatures of 57 and 75 K and total pressures of ∼40 and 70 Pa, respectively. Direct experimental information on the number and type of molecules in the clusters and on the cluster number concentration is obtained by mass spectrometric detection of nucleating clusters that form in the uniform region of Laval expansions. Only homo-molecular water clusters are observed in the mass spectra. However, as the CO2/H2O ratio increases, a significant increase in the nucleation rate is observed. A simple kinetic model suggests that this acceleration of nucleation is due to the formation of short-lived, transient hetero-molecular H2O–CO2 dimers. Comparison with homogeneous binary nucleation of toluene–CO2 and unary nucleation of H2O shows that nucleation becomes more efficient in systems with stronger intermolecular interactions and a larger number of degrees of freedom. Such studies at the molecular level will improve our understanding of homogeneous nucleation mechanisms in atmospheric and industrial processes. [ABSTRACT FROM AUTHOR]

Water freezing, initiated by ice nucleation, occurs widely in nature, ranging from cellular to global phenomena. Ice nucleation has been experimentally proven to require the formation of a critical ice nucleus, consistent with classical nucleation theory (CNT). However, the accuracy of CNT quantitative predictions of critical cluster sizes and nucleation rates has never been verified experimentally. In this study, we circumvent this difficulty by using molecular dynamics (MD) simulation. The physical properties of water/ice for CNT predictions, including density, chemical potential difference, and diffusion coefficient, are independently obtained using MD simulation, whereas the calculation of interfacial free energy is based on thermodynamic assumptions of CNT, including capillarity approximation among others. The CNT predictions are compared to the MD evaluations of brute-force simulations and forward flux sampling methods. We find that the CNT and MD predicted critical cluster sizes are consistent, and the CNT predicted nucleation rates are higher than the MD predicted values within three orders of magnitude. We also find that the ice crystallized from supercooled water is stacking-disordered ice with a stacking of cubic and hexagonal ices in four representative types of stacking. The prediction discrepancies in nucleation rate mainly arise from the stacking-disordered ice structure, the asphericity of ice cluster, the uncertainty of ice–water interfacial free energy, and the kinetic attachment rate. Our study establishes a relation between CNT and MD to predict homogeneous ice nucleation. [ABSTRACT FROM AUTHOR]

We use molecular dynamics simulations to examine the homogeneous nucleation of ice VII from metastable liquid water. An unsupervised machine learning classification identifies two distinct local structures composing Ice VII nuclei. The seeding method, combined with the classical nucleation theory (CNT), predicts the solid–liquid interfacial free energy, consistent with the value from the mold integration method. Meanwhile, the nucleation rates estimated from the CNT framework and brute force spontaneous nucleations are inconsistent, and we discuss the reasons for this discrepancy. Structural and dynamical heterogeneities suggest that the potential birthplace for an ice VII embryo is relatively ordered, although not necessarily relatively immobile. Moreover, we demonstrate that without the formation of hydrogen-bond links, ice VII embryos do not grow. [ABSTRACT FROM AUTHOR]

Molecular dynamics (MD) of the Lennard-Jones cluster in the environment of supersaturated vapor at fixed temperature and density is used for the investigation of nonisothermal nucleation. The results allow one to single out different processes occurring at different time scales, the Ornstein–Uhlenbeck fluctuations at the short time scale and a combination of slow diffusion and drift of the fluctuation packet that represents a cluster, at the long time scale. The multiscale approach is developed, in which a separate treatment of different time scales makes it possible to consider strongly correlated cluster size and temperature. This reduces the nonisothermal cluster evolution to a one-dimensional problem. The fluctuation packet drift velocity and diffusivity are calculated based on the cluster microscopic thermophysical parameters determined in this work from MD data for isothermal clusters. The proposed approach is consistent with the results of our MD simulation. [ABSTRACT FROM AUTHOR]

The crystallization of complex, concentrated alloys can result in atomic-level short-range order, composition gradients, and phase separation. These features govern the properties of the resulting alloy. While nucleation and growth in single-element metals are well understood, several open questions remain regarding the crystallization of multi-principal component alloys. We use molecular dynamics to model the crystallization of a five-element, equiatomic alloy modeled after CoCrCuFeNi upon cooling from the melt. Stochastic, homogeneous nucleation results in nuclei with a biased composition distribution, rich in Fe and Co. This deviation from the random sampling of the overall composition is driven by the internal energy and affects nuclei of a wide range of sizes, from tens of atoms all the way to super-critical sizes. This results in short-range order and compositional gradients at nanometer scales. [ABSTRACT FROM AUTHOR]

In this work, we introduce variational umbrella seeding, a novel technique for computing nucleation barriers. This new method, a refinement of the original seeding approach, is far less sensitive to the choice of order parameter for measuring the size of a nucleus. Consequently, it surpasses seeding in accuracy and umbrella sampling in computational speed. We test the method extensively and demonstrate excellent accuracy for crystal nucleation of nearly hard spheres and two distinct models of water: mW and TIP4P/ICE. This method can easily be extended to calculate nucleation barriers for homogeneous melting, condensation, and cavitation. [ABSTRACT FROM AUTHOR]

By employing brute-force molecular dynamics, umbrella sampling, and seeding simulations, we investigate homogeneous nucleation during melting and freezing of hard spheres. We provide insights into these opposing phase transitions from the standpoint of classical nucleation theory. We observe that melting has both a lower driving force and a lower interfacial tension than freezing. The lower driving force arises from the vicinity of a spinodal instability in the solid and from a strain energy. The lower interfacial tension implies that the Tolman lengths associated with melting and freezing have opposite signs, a phenomenon that we interpret with Turnbull's rule. Despite these asymmetries, the nucleation rates for freezing and melting are found to be comparable. [ABSTRACT FROM AUTHOR]

The nucleation of ice from aqueous solutions is a process essential to myriad environmental and industrial processes, but the physical factors affecting the capacity of different solutes to depress the homogeneous nucleation temperature of ice are yet poorly understood. In this work, we demonstrate that for many binary aqueous solutions of non-ionic solutes, this depression is dominated by the entropy of the liquid phase. Employing the classic Turnbull interpretation of the interfacial free energy γ ∼ T S l i q u i d − S s o l i d and estimating solution entropies with a Flory-style modification of the ideal entropy of mixing that accounts for solute size effects, we demonstrate that mixing entropy alone predicts experimental homogeneous nucleation temperatures across a wide variety of non-ionic solutions. We anticipate that this physical insight will not only enhance a fundamental understanding of homogeneous nucleation processes across fields but also open new avenues to the rational design of aqueous solutions for desired nucleation behaviors. [ABSTRACT FROM AUTHOR]

The large discrepancy among the nucleation kinetics extracted from experimental measurements and computer simulations and the prediction of the classical nucleation theory (CNT) has stimulated intense arguments about its origin in the past decades, which is crucially relevant to the validity of the CNT. In this paper, we investigate the atomistic mechanism of the nucleation in liquid Al in contact with amorphous substrates with atomic-level smooth/rough surfaces, using molecular dynamics (MD) simulations. This study reveals that the slightly distorted local fcc/hcp structures in amorphous substrates with smooth surfaces can promote heterogeneous nucleation through a structural templating mechanism, and on the other hand, homogeneous nucleation will occur at a larger undercooling through a fluctuation mechanism if the surface is rough. Thus, some impurities, previously thought to be impotent, could be activated in the homogeneous nucleation experiments. We further find that the initial growth of the nucleus on smooth surfaces of amorphous substrates is one order of magnitude faster than that in homogeneous nucleation. Both these factors could significantly contribute to the discrepancy in the nucleation kinetics. This study is also supported by a recent study of the synthesis of high-entropy alloy nanoparticles assisted with the liquid metal Ga [Cao et al., Nature 619, 73 (2023)]. In this study, we established that the boundary existed between homogeneous and heterogeneous nucleation, i.e., the structural templating is a general mechanism for heterogeneous nucleation, and in its absence, homogeneous nucleation will occur through the fluctuation mechanism. This study provides an in-depth understanding of the nucleation theory and experiments. [ABSTRACT FROM AUTHOR]

We theoretically investigate homogeneous crystal nucleation in a solution containing a solute and a volatile solvent. The solvent evaporates from the solution, thereby continuously increasing the concentration of the solute. We view it as an idealized model for the far-out-of-equilibrium conditions present during the liquid-state manufacturing of organic electronic devices. Our model is based on classical nucleation theory, taking the solvent to be a source of the transient conditions in which the solute drops out of the solution. Other than that, the solvent is not directly involved in the nucleation process itself. We approximately solve the kinetic master equations using a combination of Laplace transforms and singular perturbation theory, providing an analytical expression for the nucleation flux. Our results predict that (i) the nucleation flux lags slightly behind a commonly used quasi-steady-state approximation. This effect is governed by two counteracting effects originating from solvent evaporation: while a faster evaporation rate results in an increasingly larger influence of the lag time on the nucleation flux, this lag time itself is found to decrease with increasing evaporation rate. Moreover, we find that (ii) the nucleation flux and the quasi-steady-state nucleation flux are never identical, except trivially in the stationary limit, and (iii) the initial induction period of the nucleation flux, which we characterize as a generalized induction time, decreases weakly with the evaporation rate. This indicates that the relevant time scale for nucleation also decreases with an increasing evaporation rate. Our analytical theory compares favorably with results from a numerical evaluation of the governing kinetic equations. [ABSTRACT FROM AUTHOR]

Colloidal crystals formed with attractive interactions are used for in-situ observations of homogeneous nucleation processes in density-matched dispersion. We found globular and plate-like polycrystalline clusters stably suspended in the dispersion. Both clusters rotated randomly and moved freely with suspending in the dispersion. They were probably formed through homogeneous nucleation processes. [ABSTRACT FROM AUTHOR]

Rationally designing a current collector that can maintain low lithium (Li) porosity and smooth morphology while enduring high‐loading Li deposition is crucial for realizing the high energy density of Li metal batteries, but it is still challengeable. Herein, a Li2ZnCu3 alloy‐modified Cu foil is reported as a stable current collector to fulfill the stable high‐loading Li deposition. Benefiting from the in situ alloying, the generated numerous Li2ZnCu3@Cu heterojunctions induce a homogeneous Li nucleation and dense growth even at an ultrahigh capacity of 12 mAh cm−2. Such a spatial structure endows the overall Li2ZnCu3@Cu electrode with the manipulated steric hindrance and outmost surface electric potential to suppress the side reactions during Li stripping and plating. The resultant Li||Li2ZnCu3@Cu asymmetric cell preserves an ultrahigh average Coulombic efficiency of 99.2 % at 3 mA cm−2/6 mAh cm−2 over 200 cycles. Moreover, the Li‐Li2ZnCu3@Cu||LiFePO4 cell maintains a cycling stability of 87.5 % after 300 cycles. After coupling with the LiCoO2 cathode (4 mAh cm−2), the cell exhibits a high energy density of 407.4 Wh kg−1 with remarkable cycling reversibility at an N/P ratio of 3. All these findings present a doable way to realize the high‐capacity, dendrite‐free, and dense Li deposition for high‐performance Li metal batteries. [ABSTRACT FROM AUTHOR]

We report on discovering the homogeneous boiling within a liquid film residual resting in equilibrium over a melting ice block. This phenomenon was induced via longwave infrared radiation generated by a continuous wave laser. This investigation employed a high-speed camera and the Schlieren visualization technique. The study discovered that the presence of ice substantially lowered the minimum power intensity required for homogeneous nucleation to occur. This observation is counterintuitive, as one might intuitively believe ice presence would result in enhanced cooling, demanding a higher power to initiate boiling. We offer three reasons for this observation: (1) the suppression of convective dissipation of the heat via the ice below the melted water, (2) instabilities caused by substantial temperature gradients between the irradiated meltwater and ice surface, and (3) instabilities caused by pressure gradients due to uneven melting of the ice surface. The effect of impurities was also tested by adding borax to the ice. Borated ice exhibited homogeneous and heterogeneous boiling simultaneously, demonstrating an even lower power intensity to initiate thermocavitation. [ABSTRACT FROM AUTHOR]

Recent manufacturing of perovskite solar cells (PSC) is moving beyond a spin coating technique. Among several new methods of the large‐area PSCs, inkjet printing (IJP) has emerged as a promising alternative to spin coating due to the high degree of control on printed film area and low material waste. In the IJP of PSCs, one important question is how to remove redundant excess solvent and facilitate the crystallization of the perovskite phase. Along with IJP, an antisolvent bathing is employed. This work reports how the IJP parameters and antisolvent bathing compositions affect the microstructure and initial efficiency of inkjet‐printed PSCs. The halide perovskite films are submerged in the antisolvent of different temperatures to observe the formation of an intermediate phase and the evolution of perovskite phase. By observing the phase evolution using X‐Ray diffraction, an optimized antisolvent bath duration is achieved for diethyl ether (DE) condition. An enhanced power conversion efficiency (PCE) and larger grain size with two sequential passes of inkjet‐deposited perovskite are also reported, and the dissolution of homogeneous nucleation sites as a mechanism for larger grains is proposed. Finally, with multipass IJP and cold antisolvent DE bathing, a champion device with 15.02% PCE is achieved. [ABSTRACT FROM AUTHOR]

Designing an efficient modification molecule to mitigate non‐radiative recombination at the NiOx/perovskite interface and improve perovskite quality represents a challenging yet crucial endeavor for achieving high‐performance inverted perovskite solar cells (PSCs). Herein, we synthesized a novel fullerene‐based hole transport molecule, designated as FHTM, by integrating C60 with 12 carbazole‐based moieties, and applied it as a modification molecule at the NiOx/perovskite interface. The in situ self‐doping effect, triggered by electron transfer between carbazole‐based moiety and C60 within the FHTM molecule, along with the extended π conjugated moiety of carbazole groups, significantly enhances FHTM's hole mobility. Coupled with optimized energy level alignment and enhanced interface interactions, the FHTM significantly enhances hole extraction and transport in corresponding devices. Additionally, the introduced FHTM efficiently promotes homogeneous nucleation of perovskite, resulting in high‐quality perovskite films. These combined improvements led to the FHTM‐based PSCs yielding a champion efficiency of 25.58 % (Certified: 25.04 %), notably surpassing that of the control device (20.91 %). Furthermore, the unencapsulated device maintained 93 % of its initial efficiency after 1000 hours of maximum power point tracking under continuous one‐sun illumination. This study highlights the potential of functionalized fullerenes as hole transport materials, opening up new avenues for their application in the field of PSCs. [ABSTRACT FROM AUTHOR]

[Display omitted] Liquid-liquid phase separation is a key phenomenon in the formation of membrane-less structures within the cell, appearing as liquid biomolecular condensates. Protein condensates are the most studied for their biological relevance, and their tendency to evolve, resulting in the formation of aggregates with a high level of order called amyloid. In this study, it is demonstrated that Human Insulin forms micrometric, round amyloid-like structures at room temperature within sub-microliter scale aqueous compartments. These distinctive particles feature a solid core enveloped by a fluid-like corona and form at the interface between the aqueous compartment and the glass coverslip upon which they are cast. Quantitative fluorescence microscopy is used to study in real-time the formation of amyloid-like superstructures. Their formation results driven by liquid–liquid phase separation process that arises from spatially heterogeneous distribution of nuclei at the glass-water interface. The proposed experimental setup allows modifying the surface-to-volume ratio of the aqueous compartments, which affects the aggregation rate and particle size, while also inducing fine alterations in the molecular structures of the final assemblies. These findings enhance the understanding of the factors governing amyloid structure formation, shedding light on the catalytic role of surfaces in this process. [ABSTRACT FROM AUTHOR]

Gas‐quenching of perovskite wet films is widely used in upscaling perovskite solar cells (PSCs). However, due to uneven and turbulent gas stream generated by traditional approaches through air knife or air gun, it is a challenge to induce homogeneous nucleation and produce high‐quality perovskite films suitable for large‐area PSCs. Here this work presents a semi‐sealed gas quenching (SSGQ) strategy that produces homogeneous low‐velocity large‐area high‐pressure gas flow to extract low‐boiling‐point solvents effectively, while leaving behind perovskite intermediates undisturbed that then turn into large crystalline grains. As a result, the SSGQ‐processed perovskite films exhibit improved crystallinity and reproducibility, suppressed defect density and residual stress, as well as compact buried interface and large‐scale uniformity. Such blade‐coated large‐area (1.0 cm2) PSCs with carbon and metal electrodes achieve high power conversion efficiencies (PCEs) of 19.5% and 23.3% (20.5% and 24.2% for 0.04 cm2), both with the lowest PCE loss of ≤1.0% among reported works. This work presents a scalable and affordable approach for fabricating high‐quality perovskite films and high‐performance perovskite photovoltaics, paving the way to PSC commercialization. [ABSTRACT FROM AUTHOR]

The present work aims to extend the parameterisation of homogeneous ice nucleation introduced in Dolaptchiev et al. (2023) by incorporating variable ice mean mass and generalizing the approach under different conditions. The proposed method involves introducing an empirically derived correction based on a large data set of parcel model simulations. The method is validated against ensemble simulations using double-moment ice microphysics, showing a mean deviation of less than 16 % from the reference solution, with robust performance across a range of conditions. The uncertainty of the extended parameterisation is evaluated for the increasing integration time steps. The method remains computationally efficient and produces sufficiently accurate results, even with larger time steps, making it suitable for integration into numerical weather prediction models. It is shown that the generalized approach not only provides a good representation of individual nucleation events but also effectively captures the statistics across the ensemble data. The prediction of ice mixing ratio is also assessed against the reference full double-moment system results. Despite a significant error in the initial prediction, it is demonstrated that the integration of the system over several time steps equilibrates the inconsistencies. This refined parameterisation offers a more accurate prediction of ice number concentration and ice mixing ratio and is not limited to gravity wave induced perturbations and can be supplemented by other relevant dynamical effects, such as turbulence. [ABSTRACT FROM AUTHOR]

[Display omitted] Graphene Oxide (GO)-templated deposition of inorganic materials through synthesis on dispersed single sheets of GO is often complicated by the loss of the desired 2D morphology owing to the coagulation of GO sheets at high salt concentrations and non-templated homogenous nucleation. Modifying GO with anionic polymer is expected to solve both problems by i) enhancing electrostatic(steric) stabilization upon exposure to high concentrations of the ionic precursors, and ii) offering additional nucleation sites at the grafted anionic moieties to avoid homogeneous secondary nucleation. GO was grafted with branched copolymers of poly(ethylene glycol) methacrylate (PEGMA 500) and diethylene glycol dimethacrylate (DEGDMA) and ω -vinyl terminated methacrylic acid macromonomer (P(MAA)), the latter serving as an addition-fragmentation chain transfer agent. The colloidal stability of GO dispersions in water toward salt was evaluated before and after modification. Precipitation of calcium phosphate (CaP) was performed by incubating modified GO in the precursor solutions. The conditions were optimized to maximize the nucleation selectively onto GO without homogeneous CaP nucleation and coagulation of the GO-sheets. The copolymer grafted GO-sheets shows superior colloidal stability when dispersed in water. No aggregation occurs in the incubating ionic CaP precursor solutions. The optimum templated deposition of CaP onto the GO sheets by precipitation is to add a second shot of precursors after the nucleation stage to obtain GO sheets fully decorated with calcium phosphate nanorods without self-nucleation. Via the careful design on the GO modification and incubation process, the growth of calcium phosphate nanorods were confined in the desired 2D order exclusively, hereby achieving the goal of an efficient GO-templated synthesis. [ABSTRACT FROM AUTHOR]

In practical applications, intermetallic compounds like Laves phase and metal carbides adversely affect the performance of nickel‐based superalloys. Using a high‐temperature confocal laser scanning microscope, the solidification process of as‐cast GH3625 alloy containing Mg at different cooling rates (−20, −35, and −50 °C min−1) is studied. Fitting curves of the volume fraction of the solid phase with solidification temperature before and after Mg treatment are obtained. Trends of solid phase transformation rates with solidification temperature are determined. Differential scanning calorimetry is employed to analyze and statistically evaluate the melting temperature range and enthalpy of each phase during the melting process. Experimental results demonstrate that Mg treatment significantly accelerates the alloy solidification at the cooling rates of −20 and −35 °C min−1, while reducing the area of residual liquid phase at the same solidification temperature, disrupting the Laves/NbC eutectic relationship, and regularizing NbC morphology, transitioning its distribution from aggregation to dispersion. After Mg treatment, the precipitation of the Laves phase is significantly reduced. As a result, the influence mechanism of Mg treatment on the phase transformation and microstructure of GH3625 is clarified based on homogeneous nucleation theory. [ABSTRACT FROM AUTHOR]

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This study explores the mechanism behind the generation of pressure pulses on the outer surface of a molten metal droplet when immersed in water. The absence of any external trigger is assumed, and the droplet is surrounded by a vapor layer with surface hydrodynamic waves at the vapor-liquid interface. The study examines the heating conditions of a cylindrical column of water used to model a volume of cold liquid interacting with a hot metal surface, which explosively boils upon direct contact. Within the framework of classical homogeneous nucleation theory, the relationship between pressure pulse magnitude and rise time and the size of the contact area and surface temperature of the droplet is established. A criterion for determining the magnitude of the pressure pulse is derived, showing that significant pressure pulses occur within a narrow range of values for this criterion. Experimental investigations have been conducted to measure the key parameters—such as the duration and area of contact and pressure amplitude buildup—when room-temperature water comes into contact with a hot steel surface. The experimental results are compared with the theoretical predictions. Incorporating Skripov's theory of explosive boiling into the model helps explain the relationship between the pressure pulse and contact area, only when the droplet surface temperature is near or exceeds the temperature of the maximum possible water superheating. [ABSTRACT FROM AUTHOR]

1-propanol/water mixtures over the whole composition range (0 < XV ≤ 1; XV is the 1-propanol volume fraction) are shown to be structurally and dynamically heterogeneous. By combining structural (x-ray diffraction), thermodynamic (differential scanning calorimetry) and dynamical probes (dielectric spectroscopy) we construct the pertinent phase diagram. It consists of liquid 1-propanol, liquid water, hexagonal ice and different hydrates, the latter sharing the same lattice. The phase diagram can be discussed in terms of four regimes, all having in common a droplet arrangement of the minority component. When water droplets are strongly confined by 1-propanol (regime I, 0.92 < XV ≤ 1; "soft" confinement), water is unable to crystallize. It has dynamics reminiscent to the ultra-viscous water phase known as high-density liquid (HDL). When water droplets are moderately confined (regime II, 0.75 < XV ≤ 0.92) water can crystallize via homogeneous nucleation. Strikingly, the homogeneous nucleation temperature is at 205 K, well within "no-man's land." The result is in line with earlier reports that soft confinement is the key to enter into the "no-man's land". When 1-propanol is the minority component (regimes III and IV), the structure and the dynamics are dominated by the 1-propanol/water interface with the formation of hydrates. The corresponding dynamical features suggest a link between hydrate formation and the two metastable phases of ultra-viscous water, HDL and low-density liquid. [ABSTRACT FROM AUTHOR]

Understanding the nucleation behavior of water in dilute polymeric solutions is quintessential for the development of suitable artificial ice recrystallization inhibition (IRI) agents. Although poly(vinyl alcohol) (PVA) is found to be one of the most potent biomimetic IRI agents, the molecular understanding of the nucleation behavior of water in the presence of PVA is still lacking. Here, we use molecular dynamics to elucidate the role of concentration, degree of supercooling, degree of polymerization, and amphiphilicity of PVA and PVA-like polymers on the homogeneous nucleation of water in dilute polymeric solutions using the seeding method. Using classical nucleation theory (CNT), our simulations indicate an increase in the chemical potential difference between ice and melt that favors ice nucleation. However, it also predicts a significant increase in the ice–melt interfacial energy that impedes nucleation. The relative increase in the interfacial energy dominates the increase in the chemical potential difference, which results in a decrease in the nucleation rate of water with an increase in the solute concentration. This study contradicts the previous simulation study that suggested the promotion of homogeneous ice nucleation by PVA and supports the experimental observations of the heterogeneous origins of ice nucleation. Our results also suggest the non-classical origins of ice nucleation in polymeric solutions and the limitation of the CNT in predicting heterogeneous ice nucleation in polymeric solutions. [ABSTRACT FROM AUTHOR]

The aerosol ice‐nucleus (IN) effect, affecting heterogeneous ice nucleation and ultimately shaping cloud properties and precipitation efficiency, remains poorly understood and is overlooked in most operational numerical weather models. Therefore, this study aims to investigate the role of aerosol IN effect in the "21⋅7" Henan extreme precipitation event using two simulations based on an aerosol‐aware configuration of the WRF model. One prescribed spatially uniform ice nucleation particles (INP) concentration (labeled CTL), whereas the other incorporated MERRA2 aerosol concentration fields to represent a more realistic INP spatial distribution (labeled M2), which is marked by a west‐east gradient with higher INP concentration in the west. Results show that M2 simulated heavier precipitation near Zhengzhou closer to the observation regarding both spatial distribution and intensity than the CTL simulation. This improvement is attributed to an INP‐induced feedback akin to the aerosol lifetime effect. Specifically, the M2 simulation had higher INP concentration in the west, causing increased rates of heterogeneous ice nucleation as the convection progressed from west to east. This released additional latent heat, intensifying the convection and subsequently enhancing homogeneous ice nucleation, yielding more but smaller cloud ice particles in M2. These ice particles had reduced sedimentation speeds and lower aggregation rates, suppressing precipitation upstream of Zhengzhou. The intensified convection, carrying more water, propagated eastward, ultimately resulting in extremely heavy precipitation near Zhengzhou. This study underscores the aerosol IN effect on cloud microphysics, convection intensity, and regional rainfall distribution, elucidating the crucial role of aerosol‐meteorology coupling in accurately simulating moderate deep convective cloud precipitation. Plain Language Summary: Aerosols can directly or indirectly influence the formation of precipitation by serving as cloud condensation nuclei (CCN) and ice nucleation particles (INP). However, current numerical weather predictions often overlook the impact of aerosols, especially for INP. To capture the spatiotemporal distribution and relationship between aerosol fields and extreme precipitation, we coupled the dust aerosol reanalysis from MERRA2 with the WRF model, using realistic INP concentration to simulate the "21⋅7" event in Henan on 20 July 2021. Results show that a realistic INP concentration can improve the precipitation simulation in terms of spatial distribution and intensity. This paper proposes a mechanism of aerosol IN effect similar to the CCN effect. The precipitation was delayed and became heavier near Zhengzhou. This study emphasizes aerosol IN effect on cloud microphysics and precipitation and also elucidates the critical role of aerosol‐meteorological coupling in accurately modeling precipitation from moderate deep convective clouds. Key Points: The aerosol ice‐nucleus effect may play an important role in the "21⋅7" Henan extreme precipitation eventRealistic ice nuclei concentration improves the simulation of precipitation intensity and spatial distribution in deep convective systemHigher ice nuclei concentration may suppress early stage precipitation by forming more ice particles and enhance late‐stage precipitation [ABSTRACT FROM AUTHOR]

Sluggish redox kinetics and severe polysulfide shuttling are major hurdles for the commercialization of lithium–sulfur (Li–S) batteries. Transition‐metal compound catalysts offer a promising solution by providing excellent polysulfide adsorption capabilities, outstanding catalytic activities, and homogeneous nucleation control of Li2S2/Li2S. The electronic structure of transition‐metal sites in catalysts can also be fine‐tuned through bi‐metallic coupling, which can further improve the catalytic activities. In this study, bi‐metallic nickel molybdenum phosphide is co‐synthesized with Li2S and carbon through a carbothermal reduction process, forming a cathode composite (Li2S @ NixMoyPz @ C). This process is not only advantageous for large‐scale manufacturing due to its simplicity, but also ensures homogeneous integration and distribution of the catalyst within the cathode composite. Furthermore, applying Li2S as an active material allows the creation of an anode‐free cell configuration, enhancing the overall cell energy density. The anode‐free cell with the Li2S @ NixMoyPz @ C composite cathode demonstrates an outstanding capacity retention of 50% over 300 cycles at a negative‐to‐positive capacity (N/P) ratio of 1. Additionally, the bi‐metallic phosphide integrated Li2S cathode composite delivers a remarkable anode‐free pouch cell performance of 703 mA h g−1 (on Li2S basis) under the challenging conditions of an E/Li2S ratio of 4.5. [ABSTRACT FROM AUTHOR]

The paper presents the results of solving the problem of liquid evaporation and its vapor condensation in a closed space with regard to the formation of droplets in it as a result of homogeneous vapor nucleation, obtained by jointly solving the Boltzmann kinetic equation and the equations of continuum mechanics. The kinetics of homogeneous vapor condensation is described by the corresponding system of moment equations. Calculations for water have shown that in the case where the evaporation surface temperature exceeds 330 K, volume condensation of vapor occurs with high intensity, which leads to significant changes in the profiles of its parameters. [ABSTRACT FROM AUTHOR]

The practical implementation of Li metal anode has long been hindered by the significant challenges of notorious dendritic Li growth and severe interphase instability during repeated cycling. Herein, a highly lithiophilic NiSe‐modified host has rationally been constructed to stabilize Li metal by the facile mechanical rolling strategy. The in situ configurated high‐flux Li2Se‐enriched interphase layer can facilitate the fast interfacial charge transfer, high Li plating/stripping reversibility and homogeneous Li nucleation/growth. Consequently, the achieved modified Li metal demonstrates ultrahigh rate capability (10 mA cm−2) and ultralong‐term cycling stability (6600 cycles) with dendrite‐free Li deposition. The Li|LiFePO4 (LFP) cell exhibits an extraordinarily long lifespan cycling stability over 500 cycles with an ultra‐low decay rate of only ≈0.0092% per cycle at 1 C. Furthermore, the 4.5 V high‐voltage Li|LiCoO2 pouch cell with a high areal capacity (≈1.9 mAh cm−2) still reveals an impressively prolonged cyclability over 200 cycles even under the harsh test condition of low negative‐to‐positive‐capacity (N/P) ratio of ≈3.4 and lean electrolyte of ≈5.5 µL mAh−1. This work provides a facile and scalable strategy toward a highly stable Li metal anode for reliable practical usage. [ABSTRACT FROM AUTHOR]

High‐aluminum advanced high‐strength steels have received increasing interest due to their excellent combination of strength and ductility. The control of nonmetallic inclusions in steel is among the most important issue for the production of high‐aluminum steel. This study proposes a model for the evolution of size distributions of AlN inclusions during solidification of steel based on the Kampmann–Wagner numerical model and microsegregation calculation. Both homogeneous (pure AlN) and heterogeneous precipitations (AlN+oxide or MnS) are described using homogeneous nucleation and free growth models of Greer et al. respectively. The model is applied to calculate the size distributions of AlN in high‐Al (up to 5%) Fe–Cr–Al steels and high‐ and medium‐manganese steels and validated by the experimental data in the literature. The model correctly describes the influence of cooling rates on the precipitation of AlN in Fe–Cr–Al steels and high‐manganese steels, and the sizes of AlN are reduced and the number densities of AlN inclusions are increased by increasing the cooling rate. The effects of nitrogen and aluminum concentration in medium‐manganese steel on inclusion precipitation are investigated by the model calculation. The increases in nitrogen and aluminum concentration facilitate the homogeneous precipitation of AlN inclusions. [ABSTRACT FROM AUTHOR]

Among the REBa2Cu3O7‐δ (REBCO or RE123, RE = rare earth element) family, SmBCO is preferably used in top‐seeded melt‐growth (TSMG) because of its outstanding property and more controllable stoichiometry 123. Nevertheless, the refinement of Sm2BaCuO5 (Sm211) particles has been challenging for high‐performance SmBCO bulks. Conventional precursor powders (SmBa2Cu3O7‐δ plus Sm2BaCuO5) intrinsically result in enlarging Sm2BaCuO5 particles due to their coarsening and epitaxial growth during the heating process. Here, we used modified precursor powders (MPPs, Sm2O3 plus Ba2Cu3O5) in air‐processed TSMG, in which there is neither Sm211 in the beginning nor related enlargement during heating. Consequently, the nucleation catastrophe of Sm211 occurred above the peritectic temperature, which in situ formed, possessing naturally small size. Further, aiming to suppress the Sm/Ba substitution, Ba‐rich MPP, substituting Ba2Cu3O5 with Ba3Cu4O7) was employed, producing an excellent SmBCO bulk with a diameter of 24 mm: levitation force of 51.5 N and trapped field of 0.537 T. Optical micrographs and quantitative analyses confirmed the superior refinement and distribution of Sm211 particles in SmBCO bulks. Most importantly, new strategies in this work are widely applicable for developing cost‐effective and high‐performance other REBCO bulk superconductors. [ABSTRACT FROM AUTHOR]

The popularization of lithium metal anode has been limited due to uneven deposition processes and lithium dendrites. Guiding homogeneous nucleation during the initial plating stage of lithium is vital to obtain a stable lithium metal anode. Herein, an ultra-thin dipole layer that can be used to regulate the diffusion layer is prepared by anodizing and strong polarization on a titanium foil collector. It is demonstrated that the vertical distributions of ionic concentration and electrostatic potential on the nBTO@Ti electrode are modulated by the ultrathin dipole layer, leading to uniform diffusion of lithium ions and reduction of overpotential. Consequently, a uniform lithium nucleation and plating process are achieved on a polarized BaTiO3 collector, which is verified by microscopy. The average coulombic efficiency of the deposition-dissolution process is as high as 98.3% for 300 cycles at 0.5 mA cm−2. Moreover, the symmetrical cell shows flat potential platforms of 25 mV for 1000 cycles at 0.5 mA cm−2. Full cell with LiFePO4 as cathode also reveals excellent electrochemical performances with a steady discharge capacity of 120 mAh g−1 at 1 C and a high capacity retention of 93.3% after 200 cycles. [ABSTRACT FROM AUTHOR]

Cirrus clouds are of great importance to the global climate, with their net radiative forcing strongly dependent on the microphysical properties that are related to the ice‐nucleating regime. However, the influence of long‐range transport of dust on primary ice formation in cirrus clouds is limitedly understood, specifically over the clean remote ocean regions. Here, two case studies show that transpacific Asian dust can impact the ice formation of cirrus clouds over the central Pacific based on Cloud‐Aerosol Lidar with Orthogonal Polarization and Cloud Profiling Radar (CPR, CloudSat) observations. One case shows a well‐developed horizontally extended cirrus embedded in a pure dust layer, with an average dust‐related ice‐nucleating particle concentration (INPC) of 7 L−1 and 96 L−1 for an ice saturation ratio Si of 1.15 and 1.25, respectively; ice crystal number concentration (ICNC) with diameters >25 and 100 μm (denoted as nice,25 μm and nice,100 μm) are 64 L−1 and 7 L−1, respectively. Another case shows that cirrus clouds with a much smaller horizontal extent appeared in the vicinity of polluted dust, with an average INPC of 42–310 L−1 for the typical higher Si of 1.25–1.35 by considering a tenfold reduction of the ice nucleation efficiency of ice crystals; nice,25 μm and nice,100 μm are 168 L−1 and 20 L−1, respectively. The estimated INPC and ICNC values suggest the dominance of ice formation by dust‐induced heterogeneous nucleation, proving that the long‐range transport of dust toward the upper troposphere and the potential influence on cirrus formation over the central Pacific should be well considered in atmospheric models. Plain Language Summary: Cirrus clouds are vital to the global radiative balance. Their net radiation effect is very uncertain, depending on the microphysical properties that are mainly determined by the ice nucleation mechanism, that is, heterogeneous and homogeneous ice nucleation. In this work, two dust‐cirrus interaction cases are studied with the combinational observations of space‐borne lidar and radar. Over the remote central Pacific, where is generally very clean, we show that the long‐range transported Asian dust can significantly influence the ice nucleation at cirrus height by acting as efficient ice‐nucleating particles (INPs). The estimated number concentrations of INPs and ice crystals reveal that dust‐induced heterogeneous nucleation is dominant in ice formation, which should thus be better considered in atmospheric and climate models. Key Points: Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP)‐CloudSat observations corroborate that dust in the outflow regime of Asia can influence cirrus formation over the central PacificCALIOP observations indicate the strongest dust occurrence in the upper troposphere over the Pacific during the spring seasonDust transport toward the upper troposphere and the potential impact on cirrus formation should be well considered in atmospheric models [ABSTRACT FROM AUTHOR]

[Display omitted] • SiO 2 @G-M layer on Cu collector is achieved at one-step. • SiO 2 @G-M offers a stable Li deposition stable at a high capacity of 2 mAh cm−2. • LiFePO 4 -based AFLMBs offer a specific capacity of 129.82 mAh g−1 at 0.5C after 100 cycles. Anode-free lithium metal batteries (AFLBs) have attracted considerable attention due to their high theoretical specific capacity and absence of Li. However, the heterogeneous Li deposition and stripping on the lithiophobic Cu collector hamper AFLBs in practice. To achieve a uniform and reversible Li deposition, a carbon-based layer on the Cu collector has attracted intense interest due to its high conductivity. However, the 2D single-component carbon-based interface is inadequate lithiophilic for obtaining the homogeneous Li deposition and preventing the lithium dendrite from piercing the separator. Herein, we present a 3D embedded lithiophilic SiO 2 nanoparticles-graphene nanosheet matrix (SiO 2 @G-M) on the Cu collector by organic nano carbon source. In this structure, the lithiophilic SiO 2 nanoparticles as active points promote the homogeneous lithium nucleation and the 3D graphene nanosheet matrix offers homogenous electron distribution and voids to prevent the piercing. Finally, SiO 2 @G-M/Li cell shows a high coulombic efficiency of 98.62 % after 100 cycles at a high current density of 2 mA cm−2 with an areal capacity of 1 mAh cm−2. [ABSTRACT FROM AUTHOR]

Understanding the ice nucleation mechanism in the catalyst layers (CLs) of proton exchange membrane (PEM) fuel cells and inhibiting icing by designing the CLs can optimize the cold start strategies, which can enhance the performance of PEM fuel cells. Herein, mitigating the structural matching and templating effects by adjusting the surface morphology and wettability can inhibit icing on the platinum (Pt) catalyst surface effectively. The Pt(211) surface can inhibit icing because the atomic spacing of (211) crystalline surface is much larger than the characteristic distance of ice crystal, thereby mitigating the structural matching effects. A water overlayer on the Pt surface induced by the strong attraction of Pt can act as a template for ice layers and plays an important role in the icing process. Buckling of water overlayer due to the larger atomic spacing of (211) crystalline surface mitigates the templating effect and inhibits icing. Moreover, the water overlayer on the hydrophobic Pt(211) surface with fewer water molecules also mitigates the templating effect, which makes ice nucleation more difficult than homogeneous nucleation. These findings reveal the ice nucleation mechanisms on the Pt catalyst surface from the molecular level and are valuable for catalyst designs to inhibit icing in CL. [ABSTRACT FROM AUTHOR]

This study involved a numerical investigation of the homogeneous nucleation of CO2 from a CO2–Ar gas mixture in a supersonic nozzle with a throat size of 2.11 mm, a total pressure of 61.15 kPa, and a total temperature of 293.15 K. The flow conditions covered the cryogenic temperature range (∼75 K). Therefore, the surface tension of the clusters was calculated using the Tolman–Tanaka correction, and nucleation growth was evaluated considering both free molecular and continuum regimes. Numerical simulations were conducted for a wide range of CO2 mole fractions (3%–39%). In particular, the effect of the CO2 mole fraction on the condensation-shock position—approximately the Wilson point—was investigated. For 3%, 12%, 24%, and 39%, the condensation shock occurred at 0.048, 0.043, 0.046, and 0.054 m from the throat, respectively. When the mole fraction was low (≤10%), the condensation-shock position moved downstream as the mole fraction decreased. This trend was attributed to a lower nucleation rate. In contrast, when the mole fraction was high (≥10%), the condensation-shock position moved downstream as the mole fraction increased. This was because the CO2 equilibrium pressure rose more rapidly than the CO2 vapor pressure as the mole fraction increases. [ABSTRACT FROM AUTHOR]

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Ferroelectric perovskites are pivotal in diverse technological applications; however, a gap persists in our comprehension of their mechanical properties, emphasizing the need for additional exploration. In the present study, we report on the nanomechanical behavior of BiFeO 3 ceramics in the force range between 200 μN and 2 mN, including the evolution of the hardness and the reduced Young's modulus from (9.9 ± 0.4) GPa and (113.7 ± 6.9) GPa, respectively, with increasing force. A sequence of plastic-deformation mechanisms under the cube-corner probe was revealed through a first pop-in analysis in combination with a variety of electron microscopy techniques, starting with a homogeneous dislocation nucleation, multiplication and rearrangement leading to sub-grain formation, a phenomenon observed in metals but not in ceramics. [ABSTRACT FROM AUTHOR]

Homogeneous nucleation is the prominent mechanism of glaciation in cirrus and other high-altitude clouds. Ice nucleation rates can be studied in laboratory assays that gradually lower the temperature of pure water droplets. These experiments can be performed with different cooling rates, with different droplet sizes, and often with a distribution of droplet sizes. We combine nucleation theory, survival probability analysis, and published data on the fraction of frozen droplets as a function of temperature to understand how the cooling rate, droplet size, and size dispersity influence the nucleation rates. The framework, implemented in the Python code AINTBAD (Analysis of Ice nucleation Temperature for B and A Determination), provides a temperature-dependent nucleation rate on a per volume basis, in terms of approximately temperature-independent prefactor (A) and barrier (B) parameters. We find that dispersion in droplet diameters of less than an order of magnitude, if not properly included in the analysis, can cause apparent nucleation barriers to be underestimated by 50 %. This result highlights the importance of droplet size dispersion in efforts to model glaciation in the polydisperse droplets of clouds. We also developed a theoretical framework, implemented in the Python code IPA (Inhomogeneous Poisson Analysis), to predict the fraction of frozen droplets at each temperature for arbitrary droplet size dispersions and cooling rates. Finally, we present a sensitivity analysis for the effect of temperature uncertainty on the nucleation spectrum. Our framework can improve models for ice nucleation in clouds by explicitly accounting for droplet polydispersity and cooling rates. [ABSTRACT FROM AUTHOR]

To develop new criteria to distinguish different crystal nucleation mechanisms in silicate melts, we performed crystallization experiments using a synthetic hydrous (2 wt% H2O) trachybasalt and combined three-dimensional information from synchrotron X-ray computed microtomography with two-dimensional mapping of crystallographic orientation relationships (CORs) using electron backscatter diffraction. Crystallization experiments were performed at 400 MPa by cooling the melt from 1300 °C to resting temperatures of 1150 and 1100 °C and maintaining isothermal conditions for 30 min and 8 h. Three distinct titanomagnetite (Tmt) populations formed: (1) skeletal crystals, isolated or partially embedded in clinopyroxene (Cpx); (2) anhedral crystals, always attached to Cpx; (3) flattened needle-shaped crystals, embedded in Cpx. These morphologically different Tmt populations formed in response to one cooling event, with varying nucleation mechanisms and at different undercooling conditions. The clustered three-dimensional distribution of population 2 and 3 Tmt grains and the high proportion of Tmt-Cpx interfaces sharing CORs indicate that these Tmt grains heterogeneously nucleated on Cpx. The near-random three-dimensional distribution of (often isolated) population 1 Tmt grains, together with the low proportion of Tmt-Cpx interfaces sharing CORs, imply their isolated, possibly homogeneous nucleation, potentially followed by heterogeneous nucleation of Cpx on population 1 Tmt. Heterogeneous nucleation in slightly to moderately undercooled magmas should affect the sequence of crystallization as well as morphology and clustering of crystals, which may actively contribute to the variation of rheological parameters like viscosity. Finally, observed intra- and inter-sample variations in Tmt-Cpx COR frequencies indicate the potential for this parameter to record further petrological information. [ABSTRACT FROM AUTHOR]

Poly(vinyl alcohol) (PVA) has ice binding and ice nucleating properties. Here, we explore the dependence of the molecular size of PVA on its ice nucleation activity. For this purpose, we studied ice nucleation in aqueous solutions of PVA samples with molar masses ranging from 370 to 145 000 g mol−1, with a particular focus on oligomer samples with low molar mass. The experiments employed a novel microfluidic setup that is a follow-up on the previous WeIzmann Supercooled Droplets Observation on a Microarray (WISDOM) design by Reicher et al. The modified setup introduced and characterized here, termed nanoliter Bielefeld Ice Nucleation ARraY (nanoBINARY), uses droplet microfluidics with droplets (96 ± 4) µm in diameter and a fluorinated continuous oil phase and surfactant. A comparison of homogeneous and heterogeneous ice nucleation data obtained with nanoBINARY to those obtained with WISDOM shows very good agreement, underpinning its ability to study low-temperature ice nucleators as well as homogeneous ice nucleation due to the low background of impurities. The experiments on aqueous PVA solutions revealed that the ice nucleation activity of shorter PVA chains strongly decreases with a decrease in molar mass. While the cumulative number of ice nucleating sites per mass nm of polymers with different molar masses is the same, it becomes smaller for oligomers and completely vanishes for dimer and monomer representatives such as 1,3-butanediol, propan-2-ol, and ethanol, most likely because these molecules become too small to effectively stabilize the critical ice embryo. Overall, our results are consistent with PVA polymers and oligomers acting as heterogeneous ice nucleators. [ABSTRACT FROM AUTHOR]

We study low-salt, binary aqueous suspensions of charged colloidal spheres of size ratio Γ = 0.57, number densities below the eutectic number density nE, and number fractions of p = 1.00–0.40. The typical phase obtained by solidification from a homogeneous shear-melt is a substitutional alloy with a body centered cubic structure. In strictly gas-tight vials, the polycrystalline solid is stable against melting and further phase transformation for extended times. For comparison, we also prepare the same samples by slow, mechanically undisturbed deionization in commercial slit cells. These cells feature a complex but well reproducible sequence of global and local gradients in salt concentration, number density, and composition as induced by successive deionization, phoretic transport, and differential settling of the components, respectively. Moreover, they provide an extended bottom surface suitable for heterogeneous nucleation of the β-phase. We give a detailed qualitative characterization of the crystallization processes using imaging and optical microscopy. By contrast to the bulk samples, the initial alloy formation is not volume-filling, and we now observe also α- and β-phases with low solubility of the odd component. In addition to the initial homogeneous nucleation route, the interplay of gradients opens various further crystallization and transformation pathways leading to a great diversity of microstructures. Upon a subsequent increase in salt concentration, the crystals melt again. Wall-based, pebble-shaped β-phase crystals and facetted α-crystals melt last. Our observations suggest that the substitutional alloys formed in bulk experiments by homogeneous nucleation and subsequent growth are mechanically stable in the absence of solid–fluid interfaces but thermodynamically metastable. [ABSTRACT FROM AUTHOR]

In this work, we shall estimate via computer simulations the homogeneous nucleation rate for the methane hydrate at 400 bars for a supercooling of about 35 K. The TIP4P/ICE model and a Lennard-Jones center were used for water and methane, respectively. To estimate the nucleation rate, the seeding technique was employed. Clusters of the methane hydrate of different sizes were inserted into the aqueous phase of a two-phase gas–liquid equilibrium system at 260 K and 400 bars. Using these systems, we determined the size at which the cluster of the hydrate is critical (i.e., it has 50% probability of either growing or melting). Since nucleation rates estimated from the seeding technique are sensitive to the choice of the order parameter used to determine the size of the cluster of the solid, we considered several possibilities. We performed brute force simulations of an aqueous solution of methane in water in which the concentration of methane was several times higher than the equilibrium concentration (i.e., the solution was supersaturated). From brute force runs, we infer the value of the nucleation rate for this system rigorously. Subsequently, seeding runs were carried out for this system, and it was found that only two of the considered order parameters were able to reproduce the value of the nucleation rate obtained from brute force simulations. By using these two order parameters, we estimated the nucleation rate under experimental conditions (400 bars and 260 K) to be of the order of log10 (J/(m3 s)) = −7(5). [ABSTRACT FROM AUTHOR]

Methane hydrates are important from a scientific and industrial perspective, and form by nucleation and growth from a supersaturated aqueous solution of methane. Molecular simulation is able to shed light on the process of homogeneous nucleation of hydrates, using straightforward molecular dynamics or rare event enhanced sampling techniques with atomistic and coarse grained force fields. In our previous work [Arjun, T. A. Berendsen, and P. G. Bolhuis, Proc. Natl. Acad. Sci. U. S. A. 116, 19305 (2019)], we performed transition path sampling (TPS) simulations using all atom force fields under moderate driving forces at high pressure, which enabled unbiased atomistic insight into the formation of methane hydrates. The supersaturation in these simulations was influenced by the Laplace pressure induced by the spherical gas reservoir. Here, we investigate the effect of removing this influence. Focusing on the supercooled, supersaturated regime to keep the system size tractable, our TPS simulations indicate that nuclei form amorphous structures below roughly 260 K and crystalline sI structures above 260 K. For these temperatures, the average transition path lengths are significantly longer than in our previous study, pushing the boundaries of what can be achieved with TPS. The temperature to observe a critical nucleus of certain size was roughly 20 K lower compared to a spherical reservoir due to the lower concentration of methane in the solution, yielding a reduced driving force. We analyze the TPS results using a model based on classical nucleation theory. The corresponding free energy barriers are estimated and found to be consistent with previous predictions, thus adding to the overall picture of the hydrate formation process. [ABSTRACT FROM AUTHOR]

Phase transitions of proteins are strongly influenced by surface chemical modifications or mutations. Human γD-crystallin (HGD) single-mutants have been extensively studied because they are associated with the onset of juvenile cataract. However, they have also provided a rich library of molecules to examine how specific inter-protein interactions direct protein assembly, providing new insights and valuable experimental data for coarse-grained patchy-particle models. Here, we demonstrate that the addition of new inter-protein interactions by mutagenesis is additive and increases the number and variety of condensed phases formed by proteins. When double mutations incorporating two specific single point mutations are made, the properties of both single mutations are retained in addition to the formation of a new condensed phase. We find that the HGD double-mutant P23VC110M self-assembles into spherical particles with retrograde solubility, orthorhombic crystals, and needle/plate shape crystals, while retaining the ability to undergo liquid–liquid phase separation. This rich polymorphism is only partially predicted by the experimental data on the constituent single mutants. We also report a previously un-characterized amorphous protein particle, with unique properties that differ from those of protein spherulites, protein particulates previously described. The particles we observe are amorphous, reversible with temperature, tens of microns in size, and perfectly spherical. When they are grown on pristine surfaces, they appear to form by homogeneous nucleation, making them unique, and we believe a new form of protein condensate. This work highlights the challenges in predicting protein behavior, which has frustrated rational assembly and crystallization but also provides rich data to develop new coarse-grained models to explain the observed polymorphism. [ABSTRACT FROM AUTHOR]

The crystallization temperature of deeply undercooled Cu–Ge alloy melts is repeatedly measured. A statistical analysis is applied on the undercooling distributions obtained from nine different compositions, ranging from the pure semimetal (Ge) to the pure metal (Cu). By considering each undercooling distribution as an inhomogeneous Poisson process, the nucleation rates for every composition are calculated. The Thompson–Spaepen model for homogeneous nucleation in binary alloys is applied, enabling the estimation of nucleation parameters, such as kinetic pre-factors and interfacial energies, as a function of composition. Furthermore, the Turnbull coefficient α, a dimensionless solid–liquid interfacial energy constant, is also calculated as a function of alloy constitution, suggesting a dependence on the liquid composition. The composition-dependent changes of α are of considerable importance, since the α is originally defined for pure systems as a quantity dependent on crystal structure, and is nevertheless used for describing nucleation kinetics of binary and glass forming multi-component alloy systems. [ABSTRACT FROM AUTHOR]