Liquid Clusters Research Articles

Theoretical and Experimental Insights into the Dissociation of 2-Hydroxyethylhydrazinium Nitrate Clusters Formed via Electrospray.

Ionic liquids are used for myriad applications, including as catalysts, solvents, and propellants. Specifically, 2-hydroxyethylhydrazinium nitrate (HEHN) has been developed as a chemical propellant for space applications. The gas-phase behavior of HEHN ions and clusters is important in understanding its potential as an electrospray thruster propellant. Here, the unimolecular dissociation pathways of two clusters are experimentally observed, and theoretical modeling of hydrogen bonding and dissociation pathways is used to help rationalize those observations. The cation/deprotonated cation cluster [HEH2 - H]+, which is observed from electrospray ionization, is calculated to be considerably more stable than the complementary cation/protonated anion adduct, [HEH + HNO3]+, which is not observed experimentally. Upon collisional activation, a larger cluster [(HEHN)2HEH]+ undergoes dissociation via loss of nitric acid at lower collision energies, as predicted theoretically. At higher collision energies, additional primary and secondary loss pathways open, including deprotonated cation loss, ion-pair loss, and double-nitric-acid loss. Taken together, these experimental and theoretical results contribute to a foundational understanding of the dissociation of protic ionic liquid clusters in the gas phase.

Hydrated Ion Clusters in Hydrophobic Liquid: Equilibrium Distribution, Kinetics, and Implications.

Hydrophilic ions in oil phase tend to be hydrated in the presence of trace water and form hydrated clusters. The present paper elucidates the equilibrium size distribution of hydrated ion clusters and the microscopic rates of adsorption and desorption of water with the help of molecular dynamics simulations. The size distribution is derived from reversible work of hydration, which is nearly constant over the hydration number except for small clusters. The intrinsic rate constants of adsorption and desorption are evaluated to be in several psec order after correcting the diffusion. The microscopic hydration properties of ions in the oil phase play key roles in chemical reactions involving both hydrophilic and hydrophobic reactants as well as in the transport and reactivity of the ions in oil phase and at the water-oil interface.

Evaporation with the formation of chains of liquid bridges

The objective of the present work is to study the drying of a quasi-two-dimensional model porous medium, hereafter called the micromodel, initially filled with a pure liquid. The micromodel consists of cylinders measuring $50~\unicode[STIX]{x03BC}\text{m}$ in both height and diameter, radially arranged as a set of neighbouring spirals and sandwiched between two horizontal flat plates. As drying proceeds, air invades the pore space and elongated liquid films trapped by capillary forces form along the spirals. These films consist of ‘chains’ of liquid bridges connecting neighbouring cylinders. They provide hydraulic connectivity between the central bulk liquid cluster and the external rim of the cylinder pattern, where evaporation takes place during a first constant-evaporation-rate drying stage. The first goal of the present paper is to describe experimentally the phase distribution during drying, notably the evolution of liquid films, which controls the evaporation kinetics (e.g. the depinning of the films from the external rim signals the end of the constant-evaporation-rate period). Then, a viscocapillary model for the drying process is presented. It is based on numerical simulations of a liquid film capillary shape and viscous flow within a film. The model shows a reasonably good agreement with the experimental data. Thus, the present study is a step towards direct modelling of the effect of films on the drying of more complex porous media (e.g. packing of beads) and should be of interest for multiphase flow applications in porous media, involving transport within liquid films.

Accurate prediction of the structure and vibrational spectra of ionic liquid clusters with the generalized energy-based fragmentation approach: critical role of ion-pair-based fragmentation

A generalized energy-based fragmentation (GEBF) approach has been developed to facilitate ab initio calculations of the ground-state energies, structures and vibrational spectra of general ionic liquid (IL) clusters. For the selected IL clusters, the accuracy of the GEBF approach with two different fragmentation schemes (ion-pair-based fragmentation and ion-based fragmentation) is evaluated with the conventional quantum chemistry calculations. Our results demonstrate that for the selected IL clusters, the GEBF approach with the ion-pair-based fragmentation scheme can provide much more accurate descriptions than that with the ion-based fragmentation scheme. The main reason for these results is that the non-integer charge behavior of each ion (cation or anion) in IL systems may induce significant errors for the GEBF approach with the ion-based fragmentation scheme, in which every ion is assumed to have an integer charge. However, this problem can be avoided by the ion-pair-based fragmentation scheme, in which each ion pair is assumed to be electrically neutral. Our illustrative results show that the GEBF approach with a dynamic ion-pair-based fragmentation scheme, in which ion pair fragments are updated for every structure, can provide satisfactory descriptions on the ground-state energies, optimized structures, and vibrational spectra of general IL clusters. The performance of the GEBF approach is found to be almost independent of the basis sets or theoretical methods, and the computational cost of the GEBF approach scales linearly with the system size at density functional theory (DFT) and second-order Møller-Plesset perturbation theory (MP2) levels. Due to its excellent parallel efficiency, the GEBF approach is expected to be a cost-effective tool for investigating the structure, vibrational spectra, as well as other properties of large IL clusters.

The self-consistent model of the anomalously slow relaxation of the systems nonwetting liquid–nanoporous medium

This paper provides information on a self-consistent model of an anomalously slow relaxation of nonwetting liquid–nanoporous medium systems with a random size distribution of pores, which introduces changes in interaction between local liquid cluster configurations in the process of liquid outflow from the porous medium. A self-consistent equation was deduced, the solution of which determines a functional connection of porous medium filling degree or time [Formula: see text]. It is shown that the anomalously slow relaxation is presented as a process of decay of interacting local metastable configurations, initialized by thermal fluctuations. As time increments, relaxation acceleration takes place with subsequent avalanche fluid outflow from the porous medium, which is connected with interaction decrease between local configurations. The dependence of the fraction of volume of liquid remaining in a porous medium changes by the power law [Formula: see text]. It is shown that for a system of water–L23 at the initial stage in the time range of [Formula: see text], an index assumes a constant value [Formula: see text], while at the following stage the acceleration of relaxation and the increase of parameter [Formula: see text] are observed.

Platinum-group minerals (PGM) in the chromitite from the Nuasahi massif, eastern India: further findings and implications for their origin

We report the first find of Al-rich chromitites in the Nuasahi massif located in the Singhbhum Craton, eastern India. Electron microprobe analyses yielded Al 2 O 3 contents between 19.86 and 25.86 wt%. The Cr 2 O 3 and Fe 2 O 3 concentrations vary (in wt %) from 34.8 to 40.67 and 5.38 to 7.05, respectively. TiO 2 content ranges from 0.04 to 0.71 wt%. The silicates interstitial to chromite consist of enstatite, magnesiohornblende and clinochlore. One sample contains 855 ppb of total platinum-group elements (PGE) and shows a chondrite-normalized PGE pattern with a slightly positive slope, with enrichment in Pt and Pd relative to Os and Ir. Ruthenium and Rh show positive and negative peaks, respectively. In agreement with the PGE distribution, the following platinum-group minerals (PGM) have been found: laurite ((Ru,Os)S 2 ), erlichmanite ((Os,Ru)S 2 ), irarsite (IrAsS), vysotskite ((Pd,Ni)S), braggite or cooperite ((Pt,Pd,Ni)S) and Pd-telluride. The PGM form small grains, less than 10 μm across, and occur associated with base metal sulphides (BMS) and rutile included in magmatic minerals, such as chromite and enstatite. The BMS occur exclusively included in chromite. Mineralogical observations suggest that the (Os, Ir, Ru), Pt- and Pd-bearing phases crystallized in the magmatic stage, before or during the precipitation of the host chromite, under relatively high sulphur fugacity. Part of the Pd, together with Te, was initially enclosed at high temperature as small clusters in the sulphide liquid and then incorporated in the crystallizing BMS. Finally, these elements precipitated as Pd-telluride blebs, as an exsolution product at lower temperatures. Rutile occurs as a minor phase in association with PGM, included in chromite or in the contact chromite–silicate. The mode of occurrence of rutile in the Nuasahi chromitite is similar to that reported from the stratiform chromitites emplaced in stable cratonic settings.

Additional Approaches to Experimental Validation of the Phenomenon of Electrochemical Phase Formation in Metals Via a Supercooled Liquid State Stage

A previously unknown phenomenon of electrochemical phase formation in metals via a supercooled liquid state stage was recently established by synthesis of experimental and theoretical findings. Essentially, this phenomenon is to be understood as follows: during metal electrodeposition onto a solid cathode in an aqueous environment, a deeply supercooled metal liquid evolves in the form of multiple liquid atomic clusters avalanching at various sites near the cathode or the growing deposit and solidifies ultra rapidly at the deposition temperature to appear in a crystalline, amorphous or quasi-crystalline phase. The unconventional nature of this phenomenon requires additional approaches to experimental validation of its existence. In this context, the intention of the investigation at hand was to perform experimental verification of the existence of the discovered phenomenon by analysis of electrodeposited metals' structural features as resulting from ultra-rapid solidification of highly supercooled liquid metal phase. The hypothesis of this study was that the structure in metals that were ultra-rapidly solidified under high supercooling has certain typical traits that distinguish it from the metals' structure evolved under ordinary conditions. Besides, the degree of supercooling in metal electrodeposition must be a major factor that may affect characteristics of the structure. Idea One and Its Realization. It is well-known that metal solidification at a minor degree of melt supercooling follows a dendritic pattern due to morphological instability at solid-melt interface. At high supercooling, however, dendritic solidification gives way to spherulitic one. In this case the spherulites generally occur at the metal-crucible interface. Additionally, quasicrystals occur in ultra-rapid quenching of highly supercooled melts. Therefore, if metals indeed pass a supercooled liquid state stage during electrochemical phase formation and are rapidly solidified at the deposition temperature, then their layers adjacent to the cathode should contain spherulites and quasicrystals. To verify this idea, cathode-adjacent layers in electrodeposited copper, lead and cobalt were investigated. It has been established that spherulites and pentagonal quasicrystals occur in cathode-adjacent metal layers, which is typical of metals produced by ultra-rapid solidification of a highly supercooled liquid metal phase (Fig. 1). Idea Two and Its Realization. It is well-known that as the deposited layer grows in thickness, the spherulites disappear and the deposit then develops in druse form. For a more convincing argument in favor of the existence of an intermediate liquid phase in metal being electrodeposited, one should completely prevent transition from the spherulitic growth process to the drusy one with increasing thickness of deposit and thus produce a purely spherulitic deposit. The above idea was realized in complex alloying of iron with nickel and chromium during electrodeposition. It has been shown that electrodeposited metals appear solely in spherulitic form if transition from spherulitic to drusy growth form with increasing deposit thickness is prevented completely. Idea Three and Its Realization. Based on the concept of electrochemical phase formation in metals via a supercooled liquid state stage, it may be expected that the enrichment of crystalline defects will increase with higher supercooling in electrodeposition. This is because the high nucleation rate at greater supercooling values dominates over the linear crystal growth rate. Accordingly, increasing supercooling must lead to higher vacancy concentrations, greater dislocation densities and smaller grain sizes in metals being electrodeposited. The above idea was verified in experiments on a number of metals (cobalt, chromium, copper, iron and nickel) which were deposited under ordinary conditions from ordinary electrolytes with no organic additions. Consistent change has been found in characteristics of point, linear and planar crystalline defects as degree of supercooling is increased in electrodeposition. The obtained experimental results prove the existence of the phenomenon of electrochemical phase formation in metals via a supercooled liquid state stage. Fig 1. SEM image of pentagonal quasicrystal in the cathode-adjacent layers of the electrodeposited copper Figure 1

Analyzing multistep homogeneous nucleation in vapor-to-solid transitions using molecular dynamics simulations.

In this paper, we present multistep homogeneous nucleations in vapor-to-solid transitions as revealed by molecular dynamics simulations on Lennard-Jones molecules, where liquidlike clusters are created and crystallized. During a long, direct NVE (constant volume, energy, and number of molecules) involving the integration of (1.9-15)×10^{6} molecules in up to 200 million steps (=4.3 μs), crystallization in many large, supercooled nanoclusters is observed once the liquid clusters grow to a certain size (∼800 molecules for the case of T≃0.5ɛ/k). In the simulations, we discovered an interesting process associated with crystallization: the solid clusters lost 2-5% of their mass during crystallization at low temperatures below their melting temperatures. Although the crystallized clusters were heated by latent heat, they were stabilized by cooling due to evaporation. The clusters crystallized quickly and completely except at surface layers. However, they did not have stable crystal structures, rather they had metastable structures such as icosahedral, decahedral, face-centered-cubic-rich (fcc-rich), and hexagonal-close-packed-rich (hcp-rich). Several kinds of cluster structures coexisted in the same size range of ∼1000-5000 molecules. Our results imply that multistep nucleation is a common first stage of condensation from vapor to solid.

Pore network modelling of molecular diffusion in a single‐block model during lean gas injection, investigating the effect of throat sorting

Based on analogy between isothermal drying of porous media and molecular diffusion in a single‐block model containing a volatile liquid during lean gas injection, a detailed procedure is presented for two‐dimensional quasi‐static pore network modelling of diffusion. A modified invasion percolation algorithm is used to account for evaporation of liquid clusters formed during gas injection process. Diffusion in gas phase, capillary‐induced flow in liquid phase, and evaporation in gas‐liquid interface were modelled to trace the movement of gas‐liquid interface and desaturation profile. Using a set of throat sizes with normal distribution, 15 cases of a regular pore network model were proposed by rearranging throat positions in the model. Results of this study indicate that diffusion time, breakthrough time, vapour partial pressure gradient, liquid saturation gradient, liquid cluster frequency, gas‐liquid interface frequency, and evaporation potential are strong functions of throat sorting. Correlation coefficient of throat size with position was used to capture the disorder of porous medium. It was shown that such a correlation coefficient is not capable of describing diffusion characteristics.

Drying of thin porous disks from pore network simulations

ABSTRACTThin porous media (TPM) are porous layers that are characterized by a small thickness, usually orders of magnitude smaller than the lateral dimensions. We present pore network simulation revealing that drying of TPM is substantially different from drying of thicker porous media because of the impact of the small thickness of only a few pore layers on the liquid phase structure during drying. The small thickness limits the long-distance connectivity within the liquid clusters and thus causes the formation of smaller clusters characterized by shorter residence times. As a result of this stronger and earlier liquid phase fragmentation the drying of TPM is shown to be significantly more sensitive to the distribution of the evaporation flux at the surface. It is also shown that the drying behavior transition from thin to thick porous media is progressive. Moreover, it is discussed how an imposed temperature distribution can be used to control the evolution of the liquid cluster distribution in a TPM and thereby the evolution of the evaporation rate.

Coordinate transformation for separating the classical phase integral and the rotational partition function of a small liquid cluster of molecules, Kazumi Nishioka, G. M. Pound and F. F. Abraham, Phys. Rev A, 1, 1542-1548(1970) : 気相からの均一核生成理論

Coordinate transformation for separating the classical phase integral and the rotational partition function of a small liquid cluster of molecules, Kazumi Nishioka, G. M. Pound and F. F. Abraham, Phys. Rev A, 1, 1542-1548(1970) : 気相からの均一核生成理論

Correction to Real-Time Observation of Protein Dense Liquid Cluster Evolution during Nucleation in Protein Crystallization

Correction to Real-Time Observation of Protein Dense Liquid Cluster Evolution during Nucleation in Protein Crystallization

Rayleigh limit and fragmentation of multiply charged Lennard-Jones clusters: Can charged clusters provide clues to investigate the stability of electrospray droplets?

The fragmentation of multiply charged clusters composed of N≤1000 Lennard-Jones particles augmented with electrostatic interactions is explored by classical Monte Carlo and molecular dynamics simulations with the stated goal of establishing possible analogies with electrospray droplets. Clusters with few charge carriers are shown to be only subject to particle ejection and their Rayleigh limit can be estimated by quantifying the loss of charged particles. On the contrary, uniformly charged clusters can both evaporate particles and undergo fission, making them better candidates to model electrospray droplets. Critical charges delimiting regions of instability of these clusters are defined from the calculation of lower order multipole moments and asymmetry parameters based on the knowledge of moments of inertia. The first discontinuity of quadrupole moments and asymmetry parameters is related to cluster elongation before twofold fission and the corresponding charge is deemed to be a good estimate of the Rayleigh limit. Octopole moments are negligible about this charge, their discontinuities arising at higher charges when threefold fissions are allowed. The size dependence of these critical charges is qualitatively predicted from Rayleigh's formula and the expression of surface energy advocated in liquiddrop models. Deviations below 15% are commonly achieved when comparing Rayleigh limits extracted from experimental data with theoretical predictions based on Monte Carlo simulations or liquiddrop models for a set of eleven atomic and molecular liquid clusters. Although manifold fission of uniformly charged clusters is unlikely close to the Rayleigh limit, successive asymmetric fissions are found to occur in conjunction with other fragmentation mechanisms, including the expansion of ring-shaped structures, at charges more than twice as large as the Rayleigh limit.

Anharmonic effects in the quantum cluster equilibrium method.

The well-established quantum cluster equilibrium (QCE) model provides a statistical thermodynamic framework to apply high-level ab initio calculations of finite cluster structures to macroscopic liquid phases using the partition function. So far, the harmonic approximation has been applied throughout the calculations. In this article, we apply an important correction in the evaluation of the one-particle partition function and account for anharmonicity. Therefore, we implemented an analytical approximation to the Morse partition function and the derivatives of its logarithm with respect to temperature, which are required for the evaluation of thermodynamic quantities. This anharmonic QCE approach has been applied to liquid hydrogen chloride and cluster distributions, and the molar volume, the volumetric thermal expansion coefficient, and the isobaric heat capacity have been calculated. An improved description for all properties is observed if anharmonic effects are considered.

Acquisition of English Consonant Clusters by Korean Children: Focusing on Speech Error Analysis

The aim of this study is to investigate production of consonant clusters by Korean young children from three to six years old. Fifty-three Korean children participated in an imitation production task and their speech productions were transcribed. In order to examine the process of acquisition their speech errors were analyzed and divided into 5 types: consonant deletion, epenthesis, substitution, coalescence and combination. The results of transcription and error analysis are as follows: 1) As the children are getting old, the number of consonant deletion in consonant cluster is decreasing. 2) Among the five different error types, vowel insertion is the most frequent, and it is more frequent in the voiced stop and liquid clusters than in the voiceless stop and liquid clusters. 3) Velars, the first consonant in the clusters, tend to replaced by bilabials, whereas the second consonant, liquids are likely to be substituted with glides. 4) /p/and /r/ can coalesce into /ʃ/. 5) More than one types of errors can be combined and produced in the consonant clusters. Based on the results of this study, some implications for the acquisition of consonant clusters were drawn.

Real-Time Observation of Protein Dense Liquid Cluster Evolution during Nucleation in Protein Crystallization

Controlled navigation in the phase diagram of protein crystallization and probing by advanced Dynamic Light Scattering (DLS) technology provided new information and more insight on the early processes during the nucleation process. The observed hydrodynamic radius distribution pattern clearly reveals a two-step mechanism of nucleation and the occurrence of liquid dense protein clusters, which were verified by transmission electron microscopy. The growth kinetics of these protein clusters, forming distinct radii fractions, is analyzed in real time. Further, the data confirmed that critical nuclei show a distinctly different radius distribution than the liquid dense clusters. The data and results provide experimental evidence that during nucleation, a formation of distinct liquid clusters with high protein concentration occur prior to a transition to crystal nuclei by increasing the internal structural order of these clusters, subsequently.

Real-Time Observation of Protein Dense Liquid Cluster Evolution during Nucleation in Protein Crystallization

Real-Time Observation of Protein Dense Liquid Cluster Evolution during Nucleation in Protein Crystallization

A Classical Density Functional Study of Clustering in Ionic Liquids at Electrified Interfaces

Ion association, leading to the formation of clusters in ionic liquids, is investigated within the framework of classical density functional theory. Clusters are incorporated into a generic coarse-grained model for imidazolium-based ionic liquids confined by planar charged surfaces. We find that the short-ranged structure adjacent to surfaces is remarkably unaffected by the degree of ion association. The physical implications of ion clustering only become apparent in equilibrium properties that depend upon the long-range screening of charge, such as the asymptotic behavior of forces between charged surfaces and the differential capacitance around low surface potentials. Surface forces show a long-range exponential decay, which depends primarily on the concentration of nonassociated ions, while the differential capacitance seems to be a sensitive function of the internal structure of clusters. Furthermore, the size of the ion clusters only slightly influences surface forces, but has a significant effect on...

Manipulation of magnetic nanorod clusters in liquid by non-uniform alternating magnetic fields.

It is discovered that a non-uniform alternating magnetic field can induce a translational motion of an anisotropic magnetic particle or cluster near a surface. Unlike a permanent magnet pulling a magnetic particle, the particle moves away from the magnetic source with a periodic fluctuation in its trajectory that varies with a frequency that is twice that of the field frequency. The moving speed can be tuned by varying the magnetic field strength and gradient, its alternating frequency, and the particle size. A hydrodynamic model is developed that can qualitatively explain all of the phenomena observed. Such a simple particle manipulation method has a great potential in applications such as cell biology and microfluidics.

Does a Defunctioning Stoma Impair Anorectal Function After Low Anterior Resection of the Rectum for Cancer? A 12-Year Follow-up of a Randomized Multicenter Trial.

Anorectal function after low anterior resection of the rectum for cancer is often impaired, and long-term outcome has not frequently been reported. We evaluated anorectal function 12 years after rectal resection with regard to whether patients had a defunctioning temporary stoma at the initial rectal resection. An exploratory cross-sectional investigation of a previously randomized study population. Twenty-one Swedish hospitals performing rectal cancer surgery during a 5-year period participated in the trial. Patients operated on with low anterior resection for cancer were included. Patients were randomly assigned to receive or not receive a temporary defunctioning stoma. We evaluated anorectal function 12 years after low anterior resection in patients who were initially randomly assigned to temporary stoma or not, by means of using the low anterior resection syndrome score questionnaire, which assesses incontinence for flatus, incontinence for liquid stools, defecation frequency, clustering, and urgency. Self-perceived health status was evaluated by the EQ-5D-3L questionnaire. Eighty-nine percent (87/98) of the patients responded to the questionnaires, including 46 with and 41 without an initial temporary stoma. Patient demography was comparable between the groups. No differences regarding major, minor, and no low anterior resection syndrome categories were found between the groups. The stoma group had increased incontinence for flatus (p = 0.03) and liquid stools (p = 0.005) and worse overall low anterior resection syndrome score (p = 0.04) but no differences regarding frequency, clustering, and urgency. The study was limited by its sample size (n = 98) based on a previously randomized trial population (n = 234). After low anterior resection for cancer, the incidence of the categories major, minor, and no low anterior resection syndrome were comparable in the stoma and the no-stoma groups. Incontinence for flatus and liquid stools was more commonly reported by patients who were randomly assigned to temporary stoma, as compared with those without, which may indicate an association between temporary stoma and impaired anorectal function. See Video Abstract at http://links.lww.com/DCR/A413.