Hydrate Crystals Research Articles

Investigation of the Influence of clathrate hydrate crystals on the Structuring of Homeopathic High Dilutions

High dilutions (HD) of drugs used in homeopathy are mostly too dilute to contain original drug molecules. But evidences support their specific biological and therapeutic effects. The reason behind this is thought to be water structure characteristic of the original drug. Spectroscopic studies indicate that the specific water structure in HDs can be resolved into free water molecules, hydrogen bonding strength of water hydroxyl, number of hydrogen bonds and clathrate hydrate crystals (CHC). HDs are prepared in EtOH water solution by serial dilution and mechanical agitation, and are called potencies. The objective of the present study is to further confirm the presence of CHCs in the two potencies of three drugs. Electronic spectra of the HDs of the potencies indicate two broad peaks and marked difference in intensities of absorption. Furior Transform Infrared (FT-IR) spectra of the test potencies and their control show difference in intensity shift and contour shape of OH stretching and bending bands. All the experimental data indicate the presence of CHCs in varying amounts in the test potencies.

Study on the hydrate inhibition effect of nano-silica in drilling fluids

Preventing hydrate crystallization in drilling fluid is the key to ensure the safety of deep water drilling. In this work, hydrate inhibition effect of nano-silica in deep water drilling fluids was measured and compared with the typical hydrate inhibitors containing KCl-PVP and EG-PVP. The three phase equilibrium and the formation kinetics of CH4 hydrate in the drilling fluids were measured. The micro-morphological features of the formed hydrates were observed by SEM. Results showed that EG-PVP drilling fluid was found to have the best thermodynamic inhibition effect on CH4 hydrate where the deviation of the equilibrium pressure in EG-PVP drilling fluid and pure water was initially 2 MPa as the temperature was below 5 °C and increased up to about 5 MPa when the temperature was 10 °C. Nano-silica had almost no thermodynamic inhibition performance on CH4 hydrate. Kinetic measurements revealed that EG-PVP and KCl-PVP drilling fluids prolonged the hydrate nucleation to more than 48 h, but failed to remain the hydrate inhibition effect after aging tests. Nano-silica was unable to prolong the nucleation time, but was effective in reducing the initial hydrate growth rate and less affected by aging tests. SEM images revealed that nano-silica prevented phase separation in hydrate growth and induced the CH4 hydrate to form a spongy-like structure which was fragile in agitated drilling fluid. Therefore, nano-silica could be viewed as a potential synergist of hydrate inhibitors.

Development of dual functional methodology for seawater desalination and salt manufacture by carbon dioxide hydrate formation

Clathrate-hydrate-based seawater desalination is a novel technology that is performed by reaction between seawater and guest compounds to obtain fresh water. This study proposed a dual functional methodology for seawater desalination and salt manufacture by using carbon dioxide clathrate hydrate. In this methodology, the clathrate hydrate formation continues until the concentration of electrolytes in unreacted brine reaches the saturated solubility for the salt precipitation. The visual observation of the clathrate hydrate formation and the salt precipitation coupled with the analysis utilizing the powder X-ray diffraction (PXRD) technique was implemented to demonstrate the methodology. The carbon dioxide clathrate hydrate formation was first performed with sodium chloride aqueous solution. The carbon dioxide clathrate hydrate crystals floated on high salinity water. This experiment was followed by the occurrence of the sodium chloride dihydrate precipitation upon the carbon dioxide clathrate hydrate formation. The formed compounds, carbon dioxide clathrate hydrate and sodium chloride dihydrate, were identified by PXRD analysis. The mass fraction of the compounds was also determined by PXRD.

Development of methods of operative determination of parameters of repeated hydrate formation in layer systems of gas hydrate deposits

The object of research is the methods of laboratory setting of the parameters of hydrate formation of well production and the design features of the equipment for its implementation. Methane hydrate is becoming a promising topic for a new energy resource. At the same time, hydrostatic formation is one of the most problematic areas in ensuring the transport of well products, and this primarily concerns the production of gas hydrate deposits. An analysis of the thermobaric parameters of the well production of gas hydrate deposits shows that when they are moved by technological lines, they are close to hydrate equilibrium, but due to the intensity of the process, the system does not have time to reach it. In addition, reservoir system water has a memory of hydrate structures, or a certain amount of gas hydrate solid phase is also present in the flow water. In this regard, a set of laboratory studies was carried out to assess the nature of the behavior of this type of systems during the re-crystallization of gas hydrate and its dissociation. Based on the results of the research, a method for the operational laboratory setting of the parameters of repeated hydrate formation in reservoir systems of gas hydrate deposits was developed. It provides for setting the parameters of mass crystallization of gas hydrate by visual fixation of the moment of appearance of the solid phase at the interfacial contact «liquid – gas». The design features of the laboratory facility for its implementation have also been developed and substantiated. The technique makes it possible to reduce the duration of the study of one sample by almost an order of magnitude (from several days to 8–10 hours). In addition to the information on the equilibrium parameters of hydrostatic formation, provided by traditional methods of laboratory research, an additional characteristic of the behavior of reservoir systems in non-equilibrium conditions has been obtained, which will help to quickly assess the risks of technogenic hydrate formation. The developed technique is important for systems that, at least, have a memory of hydrate structures. However, the preliminary transfer of a part of the water of the test sample through the gas hydrate form allows estimating the parameters of hydrate formation of any reservoir system.

Molecular simulation of methane hydrate growth confined into a silica pore

The growth of a methane hydrate seed within a silica slit pore of fixed width has been studied using All-Atom Molecular Dynamics (AA-MD). An AA force field has been used to describe the molecules of the solid silica substrate, with α-quartz crystalline structure. The crystallisation of hydrates in confined geometries is not well understood yet, and the objective of this work is to study the hydrate growth inside a silica pore using molecular simulation. Both NVT and NpT ensembles were used in the AA-MD simulations to analyse the hydrate growth from an initial seed. Results showed that the boundary conditions imposed by the nanometric slit pore yielded a hydrate with structural defects, filling the accessible space between the silica walls. The water molecules which were not incorporated to the initial seed hydrate formed a high density water layer trapped between the silica walls and the crystallised hydrate. These results provide an interesting insight into the hydrate crystallisation process in confined geometries, resembling those found in natural hydrate deposits.

CO2 capture process through hybrid gas hydrate-membrane technology: Complex approach for the transition from theory to practice

The present study is concerned with a complex theoretical and experimental evaluation of the effect of various distribution coefficients on the hydrate crystallization process retrofitted with/without membrane in the process of the capture of carbon dioxide from flue gas (N2 (83.13 mol.%)/CO2 (16.87 mol.%)) at the low-pressure. A batch reactor with a stirrer was used to perform experiments under isothermal conditions of 275.5 K and initial pressure of 3.1 MPa, the aqueous solution with a TBAB concentration of 5.0 wt% in the presence of the 1500 ppm Tween-80 were tested. The following modes were studied: the pressure-dropping separation, separation at the constant pressure, and the continuous hydrate separation. The continuous hydrate separation with/without a membrane was modeled, and its experimental verification was carried out. It was shown that using a two-stage hydrate membrane technology with an increase in the distribution coefficient, the CO2 capture cost per ton decreased and could reach 35 $/ton, with a 92 % CO2 recovery and a CO2 residue flow of 0.4 mol.%.

Effect of Vehicle Composition on the Preparation of Different Types of Dapsone Crystals for Topical Drug Delivery.

Topical formulations composed of API-pure crystals have been increasingly studied, especially in regards to the impact of particle size in penetration efficiency. Less attention, however, has been devoted to the solid-state properties of drugs delivered to the skin. In this study, we address the effect of formulation composition on the crystal form existing in topical products. Dapsone (DAP) gel formulations were prepared by mixing an organic solution containing DAP with an aqueous solution containing polymers and preservatives. The organic solvent was chosen as ethoxydiglycol (DEGEE), polyethylene glycol (PEG), or 1-methyl-2-pirrolidone (MPR) to assess the impact of composition on DAP crystal form. Such solvent variations resulted in different particulate matter. In terms of crystalline nature, the presence of DEGEE in formulations induced the crystallization of DAP hydrate, while PEG cocrystal and a mixture of hydrate and MPR solvate crystallized from the same amounts of PEG and MPR, respectively. Microscopic analysis of the gels showed heterogeneous particles with different characteristics. The behavior of gels after application to the skin was also tested. Interestingly, the different formulations seemed to accumulate in different regions of the skin. This could be the result of the effect of vehicle composition/excipients on the characteristics of the skin, such as hydration. The site-specific accumulation, however, was more pronounced in crystal-loaded gels as opposed to blank formulations. These results indicate that future studies should consider the effect of formulation composition on the API crystal form landscape as part of the strategies used to successfully target drug delivery to the skin.

THE ROLE OF SODIUM NITRATE IN COUNTERACTING THE CARBONATION OF PLASTICIZED ALKALI-ACTIVATED SLAG CEMENT CONCRETE UNDER CYCLIC INFLUENCE OF SEA WATER

Carbonation of alkali-activated slag cement concrete in marine structures under cyclic influence of sea water in actual operating conditions causes by increased risk connected with deterioration due to increased content of gel phase. Aggressive environment in case of drying under the influence of atmospheric CO2 and wetting in sea water can be classified as combination of exposure classes XC4 and XS3. These risks increase in case of fresh concretes with high consistency due to the modern requirements. The aim of this research was to determine the effectiveness of resistance to carbonation of plasticized alkali-activated slag cement concrete, exploited under cyclic influence of sea water, due to application of additive NaNO3. The advanced crystallization of hydrates in alkali-activated slag cement based both on soda ash and sodium metasilicate was shown. The state of plasticized alkali-activated slag cement concrete, which exposes to carbonation under cyclic influence of sea water in actual operating conditions, was estimated according proposed author’s methodology. The performances properties were determined after 90 cycles of wetting in sea water and drying (t= 105 ± 3 °С) under the influence of atmospheric concentration of CO2 (K≈0.04 %). The deterioration of concrete was determined by falling of flexural strength. The major falling of flexural strength in case of sodium metasilicate (by 11.8 %) compared to soda ash (by 10.3 %), used as alkaline components, is due to higher volume of gel-like phases. The effectiveness of additive NaNO3 in plasticized alkali-activated slag cement concrete after 90 cycles of drying-wetting in sea water was confirmed by positive effect on one’s properties. Advanced crystallization of gel-like phases caused the higher effectiveness of resistance to aggressive environment in the presence of sodium metasilicate compared to soda ash. The change of anion in alkaline component from carbonate to silicate ensured the lower open capillary porosity from 26.2 down to 11.9 % and the higher conditionally closed porosity from 22.9 up to 34.8 % in alkali-activated slag cement concrete while application of mentioned salt. Specified perfection of pore structure, caused by nature of alkali component, was accompanied by the higher density from 2.1 up to 2.7 %, the major compressive strength from 11.5 up to 15.0 % as well as flexural strength from 7.9 up to 11.2 % and the lower rate of carbonation from 25.0 down to 50.0 %.

Strong Hydrogen Bonds in Acetylenedicarboxylic Acid Dihydrate.

Acetylenedicarboxylic acid dihydrate (ADAD) represents a complex with strong hydrogen bonding between the carboxylic OH and the water molecule. An X-ray re-examination of the ADAD crystal structure confirms the O…O distance of the short hydrogen bonds, and clearly shows different bond lengths between the two oxygen atoms with respect to the carbon atom in the carboxyl group, indicating a neutral structure for the complex. The neutral structure was also confirmed by vibrational spectroscopy, as no proton transfer was observed. The diffraction studies also revealed two polymorph modifications: room temperature (α) and low temperature (β), with a phase transition at approximately 4.9 °C. The calculated vibrational spectra are in satisfactory agreement with the experimental spectra. A comparison of the structure and the vibrational spectra between the ADAD and the oxalic acid dihydrate reveals some interesting details. The crystal structures of both crystal hydrates are almost identical; only the O…O distances of the strongest hydrogen bonds differ by 0.08 Å. Although it was expected that a larger O…O spacing in the ADAD crystal may significantly change the infrared and Raman spectra, especially for the frequency and the shape of the acidic OH stretching vibration, both the shape and frequency are almost identical, with all subpeaks topped on the broad OH stretching vibration. The O…O distance dependent are only in- and out-of-plane OH deformations modes. The presence of polarons due to the ionized defects was not observed in the vibrational spectra of ADAD. Therefore, the origin of the broad OH band shape was explained in a similar way to the acid dimers. The anharmonicity of a potential enhances the coupling of the OH stretching with the low-frequency hydrogen bond stretching, which, in addition to the Fermi resonance, structures the band shape of the OH stretching. The fine structure found as a superposition of a broad OH stretching is attributed to Davydov coupling.

Rheology of Cyclopentane sII Hydrate Slurry in Water-in-Model Oil Emulsions: Effect of Surfactant Concentration and Water Droplet Size Relevant for Flow Assurance

Investigation on the effect of surfactant concentration and droplet size distribution in a water-in-oil emulsion system on the hydrate suspension rheology is vital to delineate the antiagglomeration role and formulate a suitable mitigation strategy for flow assurance issues. Though several studies have been reported on the effect of surfactants on hydrate kinetics, rheological characterization of hydrate systems with surfactants and their role as antiagglomerant are scarce. In this study, rheological measurements are carried out to understand the effect of a mixed surfactant system (Span80 and Tween80 with HLB value of 5.9) at varying concentrations (0.5, 1, 1.5, 2, and 3 wt %) on the structure sII cyclopentane hydrate slurry formed in a water-in-model oil emulsion with varied droplet size distribution at 265.15 K, atmospheric pressure, and γ̇ = 100 s–1. The model oil consists of light paraffin oil and toluene to represent the saturate and aromatic fractions of the crude oil. Viscosity profiles are reported during formation and dissociation of hydrate slurries, while the flow curve and viscoelasticity tests are reported for the stable hydrate slurries. The presence of a mixed surfactant system is observed to increase the maximum peak and steady-state viscosities of the hydrate slurries up to 1.5 wt % surfactant concentration due to an enhanced oil–water interface and the water bridging between hydrate particles and droplets. At higher surfactant concentration (>1.5 to 3 wt %), capillary bridge between hydrate particles in contact is diminished due to steric hindrance provided by the hydrophobic group of the surfactant adsorbed on the hydrate surface, thus reducing the hydrate slurry viscosity and acting as antiagglomerant. At higher surfactant concentration, the yield stress reduction is observed in the range of ∼44–87% from the base value. The dissociation experiments show a small depression in the hydrate dissociation temperature from 0.5 wt % to 2 wt %. For 3 wt %, the higher dissociation temperature could be due to metastable hydrate formation in addition to the surfactant molecules surrounding the hydrate crystals, delaying their dissociation.

Molecular dynamics study of electric field enhanced hydrate growth for gas storage

Clathrate Hydrates have gained much attention not only as a natural energy resource, their unique molecular structure and thermodynamic properties also hold promising applications in various industrial fields. However, sluggish formation kinetics limits the development of hydrate-based techniques, such as gas capture, separation and storage. Previous simulations and experimental studies have suggested the possibility that electric fields promote hydrate growth, but the mechanism behind the phenomenon has not been explained. To reveal the mechanism of the electric field promoting hydrate growth, the mass transfer of guest molecules and the hydrate crystal growth under the electrostatic fields are investigated by molecular dynamics simulations. Results show that electric fields with field intensities in the range of 0.4–0.9 V/nm have a significant promotion effect on methane hydrate growth. Under the effect of the electric field, the dipole direction of water molecules in the polarized hydrates is at three characteristic angles of 25, 50 and 75° from the electric field direction. Then, the orientation of the water molecules in the liquid phase approaches the characteristic angles of the hydrate crystal with the rising field intensity, which accelerates the ordering of the water molecules and the formation of hydrate cages. Methane molecules are gathered into an ellipsoidal bubble with non-uniform gas-liquid interface tension, creating a dominant channel for dissolution. Then, guest molecules can enter the bulk water by the dominant channel to aggregate with high concentrations, providing a driving force for the diffusion of guest molecules to the solid-liquid interface. In this study, the mechanism of how the electrostatic field promotes hydrate growth was revealed by molecular simulations. It provides a theoretical basis for the electric field's application in hydrate-related hydrogen and natural gas storage technologies.

A hybrid batch distillation/membrane process for high purification part 2: Removing of heavy impurities from xenon extracted from natural gas

High-purity xenon of 6 N purity grade and higher is widely used in electronics, space, and medicine. A hybrid distillation/membrane process for the purification of xenon extracted from natural gas by gas hydrate crystallization is studied experimentally and via simulations. Membrane gas separation data for xenon-containing mixtures is measured for polysulfone membrane and polyetherimide/polyimide blend membrane. Parametric analysis and process optimization are performed in Aspen Plus Dynamics™ for a middle-vessel batch distillation column with an integrated hollow fiber membrane unit implemented via Aspen Custom Modeler™. Removal of higher- and lower-boiling impurities such as ethane, carbon dioxide, propane, methane, and krypton is considered to achieve 6 N and 9 N target purity grades. Hybrid distillation/membrane process flowsheets built with a multi-stream passive heat exchanger with either retentate or permeate being returned to the column are analysed. It is shown that the operating conditions and the configuration of the hybrid process with a membrane separation treatment of heavy impurities fraction can be tailored to achieve up to 30% increase in batch productivity for the considered case studies and improve xenon recovery reaching above 99.8% as compared to standalone batch distillation, which is especially critical for higher purity grades.

Clathrate hydrate formation and crystal growth with additives

Surfactant and hydrophobic materials are often used to accelerate hydrate formation. The effects of Tween80, decanoic acid (S10) and dodecyl alcohol (C10) on hydrate crystal growth after the nucleation of hydrate are investigated in this work. The droplets with HCFC-141b enhances hydrate formation. In the cycling procedure of formation and dissociation of hydrate, the hydrate formation with Tween80 has better stability than the system without Tween80. Additives alter the growth mode of hydrate crystal. The hydrate crystals grow at almost the same rate everywhere along the crystal growth direction in the presence of the mixture of decanoic acid and dodecyl alcohol (S10-C10) or S10-C10 + Tween80. However, hydrates grow at different rates at different sites when only Tween80 is used as additive. The hydrate lateral average growth rate (HLAGR) of crystals in the presence of 1 wt% S10-C10 and 1 wt% Tween80 is higher than that in the presence 1 wt% S10-C10. The influence of additives on hydrate crystal morphology is also studied. Clathrate hydrate crystal plates is scattered when S10-C10 is added in this work. When surfactant Tween80 is added in the experimental system, there is only one big clathrate hydrate crystal plate. There are some spicules crystals on the big crystal plate surface in the system of HCFC-141b + Tween80 + H2O.

Desalination of high-salt brine via carbon materials promoted cyclopentane hydrate formation

Significant advances in seawater desalination have been made to meet the world's increasing demand for clean water. However, the accompanying hypersaline concentrate discharge has negative environmental impact and is challenging for treatment. Herein, we demonstrate the potential of hydrate-based desalination (HBD) in treating brine with concentrations up to 16 wt%. It is difficult for hydrate nucleation to occur in strong brine without nucleation agents, as this results in lengthy induction time, the challenge can be resolved using carbon materials. We found that crystallinity and surface compositions have critical impact on cyclopentane hydrate formation and desalination efficiency. Carbon material with high crystallinity is more effective in inducing hydrate nucleation in NaCl solution due to the properly tuned interface hydrogen-bonding network as confirmed by Raman spectra. The improved hydrophilic property would degrade the desalting efficiency due to the tightly trapped brine among carbon materials and hydrate crystals. Although high concentration of NaCl would hinder hydrate formation, leading to a lower water recovery, desalting efficiency unexpectedly increases due to interfacial pre-melting in the presence of salt, reaching up to 79% in 16 wt% NaCl. The findings would help to identify and fabricate the good hydrate promoters used for HBD for treating hypersaline brine.

Enhanced CO2 sequestration based on hydrate technology with pressure oscillation in porous medium using NMR

Carbon dioxide (CO2) is a dominant greenhouse gas in the atmosphere that contributes to global warming. A promising approach to mitigate CO2 emissions is CO2 capture and storage (CCS) through clathrate hydrate crystallization under the seafloor; however, numerous issues regarding the mechanisms of concentration, efficiency, and stability of CO2 hydrate sequestration in seafloor sediments remain under dispute. This study employed low-field nuclear magnetic resonance (NMR) measurements to observe the in-situ formation of CO2 hydrate using the pressure oscillation method in porous media and evaluate the carbon sequestration efficiency. Our results indicate that CO2 hydrates are preferentially formed in large pore spaces, further hindering the subsequent gas contact with water in isolated pores. Additionally, a high initial water saturation is more conducive to high-quantity CO2 hydrate capture and sequestration in a pressure variation environment with a higher driving force. The proposed pressure oscillation method could effectively break the mass transfer barriers in the later stage of hydrate formation with the help of CO2 solubility fluctuations, significantly increase the rate of later hydrate formation, and shorten the period of hydrate sequestration.

Evaluation of Conditions to Prevent the Formation of Gaseous Hydrates Using Kinetic Inhibitors

Hydrate formation in the oil and gas industry poses serious operational problems. These problems include clogging of the gas transmission path and its pressure drop. There are several ways to prevent the formation of hydrates, one of which is the use of kinetic inhibitors. These compounds inhibit the growth of hydrate crystals and prevent them from enlarging. The most important of these compounds are polyvinyl caprolactum (PVCAP) and a ternary polymer of vinyl pyrrolidene, vinyl caprolactum and dimethylaminoethyl methacrylate (VC-713). In this study, using the energy balance around a hydrate cluster and simplification, a mathematical equation for the rate of hydrate formation is obtained. The resulting equation has two parameters, model nt0 and s, which are determined using the experimental data of Ledhos et al. . In the following, using the values ​​obtained for the above parameters, the conditions for hydrate formation in raw maroon without the presence of inhibitors and also with their presence are predicted. The results show that if PVCAP inhibitors are used in raw maroon, the rate of hydrate formation is about 0.005 gmol / lit, which is 70% lower than in the case without inhibitors. For inhibitor VC-713, the amount of hydrate formed will be zero to 0.004 gmol / lit, which results in a 70 to 100% reduction in hydrate formation compared to conditions without inhibitor. Therefore, the results indicate the proper performance of the VC-713 inhibitor. Also, the effect of temperature and pressure operating parameters on the rate of hydrate formation was investigated and, as expected, increasing temperature and decreasing pressure will reduce the rate of hydrate formation.

Effects of wax on CH4 hydrate formation and agglomeration in oil–water emulsions

The solid sediments, resulted from hydrate formation and wax crystallization in crude oil, may generate catastrophic blockage in the pipeline under adverse conditions; this poses a formidable threat to the transportation of deep-sea crude oil. To shed light on the mechanism of the effects of waxes and hydrates in deep-sea crude oil under coexisting conditions, this work systematically investigates the effects of wax crystal precipitation and hydrate formation time-series on hydrate nucleation, growth, aggregation, and crystal structure in oil–water emulsions through experiments. Research results demonstrate that the time sequence of wax crystal precipitation and hydrate formation is concerned with the possibility of significant solid deposit formation; when wax crystal precipitation precedes hydrate formation, the wax crystals inhibit hydrate nucleation and growth; conversely, when hydrate formation precedes wax crystal precipitation, the wax significantly reduces hydrate particle aggregation, which in turn improves the flow characteristics of the hydrate slurry. Additionally, the microscopic analysis further reveals that the presence of wax has no effect on the crystal structure of CH4 hydrate, yet it has a significant effect on the distribution of CH4 in the cavities, i.e. it reduces the occupancy of large cages.

Carbon Capture and Storage Toward Industrialization: A Novel Continuous Process for the Production of Carbon Dioxide Clathrates

Gas hydrates have been potentially recognized for developing new technologies for CO2 capture and storage; however, the respective industrialization faces difficulties. Hydrate's crystallization is highly exothermic, 1.3 kJ tonne−1 of captured CO2, and it only occurs in a narrow window of temperatures, typically 1–5 °C. Previous works have systematically reported low space–time yields (STY) due to low specific heat and mass transfer rates of the technologies tested. Herein, NetMIX, a novel mixing technology, is used for the continuous production of CO2 hydrates. NetMIX is a structured mixer consisting of a network of unit cells comprising mixing chambers interconnected by channels. The device used here has specific heat transfer rates ranging from 107 to 108 . The setup proves to be capable of producing hydrates at a STY of 200 , two orders of magnitude larger than other technologies, resulting in a slurry with more than 20 wt% of CO2 inside the hydrates lattice. The solid is characterized, and a cubic structure I (sI) hydrate structure is detected, with no ice traces. Moreover, results indicate that the process is stable, and no plugging occurs, crucial for industrialization.

Development of microstructure and hydration processes of concrete composites for structures with high durability

The main processes necessary for the development of microstructure and hydration of concrete and their composites for use in structures with high durability, frost resistance, water resistance are analyzed. The potential development that will ensure the strength of concrete and their composites, which have been modified by a complex of fine additives in the time range up to 365 days, has been determined. The experimental formulation of the concrete mixture, which was modified by a complex of fine modifiers based on microsilica (MK) and metakaolin (MTK), was used for testing. Concrete mixing technology has also been improved. The structure of ultra-high-strength concrete is formed during physicochemical reactions, which are accompanied by the binding of free water with clinker minerals, the formation of a saturated solution of crystal hydrates and their subsequent crystallization. Determining compounds of cement structure are such hydration products as: calcium silicate hydrate with various modifications, portland, calcite. For a more complete picture of the formation of hydration phases in high-strength concrete composites and the effect of ultrafine modifiers, the microstructure of fracture surfaces and their phase composition on the 28-day aging of concrete composites were studied by scanning electron microscopy and energy-dispersive X-wave spectroscopy.
 Comparative microanalysis and elemental analysis of various concrete composites of high structural strength and density using the methods of X-ray diffraction and energy-dispersive X-wave spectroscopy. However, the presence of Al in the later stages of hydration can also lead to the formation of secondary phases. The molar ratio of CaO to SiO2 in C-S-H is one of the main parameters for determining and controlling the properties of the calcium hydrosilicate system, which can be used to characterize some parameters of concrete durability. The structure of concrete is actually the main factor that determines its mechanical properties and their security throughout the life of the structure. Regularities of formation of structure and properties are common to all types of concrete.

Harnessing Deep Learning for Optimization of Lennard-Jones Parameters for the Polarizable Classical Drude Oscillator Force Field.

The outcomes of computational chemistry and biology research, including drug design, are significantly influenced by the underlying force field (FF) used in molecular simulations. While improved FF accuracy may be achieved via inclusion of explicit treatment of electronic polarization, such an extension must be accompanied by optimization of van der Waals (vdW) interactions, in the context of the Lennard-Jones (LJ) formalism in the present study. This is particularly challenging due to the extensive nature of chemical space combined with the correlated nature of LJ parameters. To address this challenge, a deep learning (DL)-based parametrization framework is developed, allowing for sampling of wide ranges of LJ parameters targeting experimental condensed phase thermodynamic properties. The present work utilizes this framework to develop the LJ parameters for atoms associated with four distinct groups covering 10 different atom types. Final parameter selection was facilitated by quantum mechanical data on rare-gas interactions with the training set molecules. The chosen parameters were then validated through experimental hydration free energies and condensed phase thermodynamic properties of validation set molecules to confirm transferability. The ultimate outcome of utilizing this framework is a set of LJ parameters in the context of the polarizable Drude FF, which demonstrated improvement in the reproduction of both experimental pure solvent and crystal properties and hydration free energies of the molecules compared to the additive CHARMM General FF (CGenFF) including the ability of the Drude FF to accurately reproduce both experimental pure solvent properties and hydration free energies. The study also shows how correlations between difference in the reproduction of condensed phase data between model compounds may be used to direct the selection of new atom types and training set molecules during FF development.