Phase Diagram Of Water Research Articles

Solid-Liquid Phase Equilibria of the Quaternary System (LiCl + LiBO2 + Li2B4O7 + H2O) at 308.15 K: Experimental and Theoretical Prediction

The isothermal dissolution equilibrium method was employed to obtain the solubilities and physicochemical properties of the quaternary system (LiCl + LiBO2 + Li2B4O7 + H2O) at 308.15 K in this work. The dry-salt phase diagram, water-phase diagram, and physicochemical properties, including density, refractive index, and pH against composition in the quaternary system, were established for the first time. The dry-salt phase diagram includes two invariant points, five univariate solubility curves, and four single salt crystalline phase regions (LiCl·H2O, LiBO2·2H2O, LiBO2·8H2O and Li2B4O7·3H2O), respectively. In addition, the physicochemical properties of density, refractive index, and pH in the system change regularly with the changing of the lithium metaborate concentration. Based on the Pitzer model, the mixing ion parameters of θCl,B4O5(OH)4, θB(OH)4,B4O5(OH)4 and Ψ(Li,Cl,B4O5(OH)4, ΨLi,B (OH)4,B4O5(OH)4 and the predictive solubilities in the quaternary system were fitted. Although there is a slight deviation between the calculated and experimental values, the solubility of boron in the quaternary system agrees well, which provides data support for the study of the solubility of boron.

Phase Transition between Crystalline Variants of Ordinary Ice.

Water is one of the most abundant molecules on Earth. However, this common and "simple" material has more than 18 different phases, which poses a great challenge to theoretically study the nature of water and ice. We designed two reaction coordinates that can distinguish between water and various ice states and used them to efficiently sample all possible states of the system in all-atom molecular dynamics simulation at ambient temperature and pressure. Various structural and thermodynamics properties, including the water-ice phase diagrams, can thus be calculated. We also present a simple model that successfully explains the thermodynamic stability of different ice states. Our work provides effective methods and data for theoretical studies of different phases of water and ice.

Thermophysical Properties of Liquids in Not Fully Stable States—From the First Steps to the Current Trends

The present article marks the 95th anniversary of the birth of Vladimir P. Skripov, author of the classic study of superheated and supercooled liquids. It presents a discussion based on the early work carried out by Skripov and his research team in Ekaterinburg during the 1950s and 1960s. Due to their pioneering nature, these works laid the foundation for the study of metastable liquid states. For various reasons, although they remain relevant to this day, these groundbreaking works remain unknown to most non-Russian-speaking readers. As well as elucidating the behavior of the heat capacity of a solution in the liquid–liquid critical region, the presented research also concerns the characteristic features of light scattering and free-convective heat transfer in the liquid–vapor critical region of a one-component system, discussing two options for the position of the superheated liquid spinodal on the phase diagram of water, including the area of supercooled states and negative pressures. The issues involved in the discussion are united by the fluctuating nature of such phenomena. Indeed, the very possibility of their experimental study is due to a significant increase in the scale of fluctuations of the corresponding quantities when approaching the critical point or spinodal. The ongoing development of the approaches proposed in these papers for solving contemporary problems in the thermophysics of superheated liquids is discussed.

Method to prepare aqueous propolis dispersions based on phase separation

Propolis has many benefits for human health. To facilitate its oral consumption, we designed propolis-in-water dispersions to be used as nutraceuticals. Propolis was first dissolved either in ethanol or in a hydroalcoholic solution. Water being a non-solvent for propolis, its addition produced propolis precipitation. We explored the ternary phase diagram of water, propolis and ethanol to identify the line separating the one phase region where propolis is fully dissolved, and the two-phase region where a concentrated propolis solution coexists with a dilute one. Droplets rich in propolis were produced during the phase separation process under mechanical stirring induced by a rotor–stator device or a microfluidizer, and they were stabilized using gum Arabic as an emulsifier. Ethanol was finally removed by distillation under reduced pressure. Propolis dispersions in the micron and submicron size range could be obtained. They contained between 1.75 and 10.5 wt% polyphenols relative to the total mass.

Development and Evaluation of Ceftazidime Loaded Microemulsion for Parenteral Drug Delivery System

The goal of this study was to develop a parenteral microemulsion formulation of Ceftazidime antibiotics. The ceftazidime sparingly soluble in organic solvent like ethanol, DMSO, and dimethyl formamide were determined. For biological experiment, organic solvent- free aqueous solutions of ceftazidime (hydrate) are prepared by directly dissolving the crystalline compound in aqueous buffer. The peudo ternary phase diagrams of oil, surfactant, cosurfactants (Butanol/ Isopropyl alcohol mixture) and water were constructed to identify boundaries for microemulsion existence. Ceftazidime microemulsion particle size, solution viscosity and conductivity were evaluated. The microemulsion stability and haemolytic activity were examined after dilution in 5% dextrose solution for injection to 1 mg/mL ceftazidime. In vitro haemolysis studies indicated that Ceftazidime microemulsions were well tolerated by erythrocytes. The novel microemulsion formulation of Ceftazidime was developed that is suitable for parenteral administration. This new formulation could potentially have less vehicle-associated side effects that current commercial formulation of Ceftazidime based on Cremophor® EL and isopropyl alcohol solution.

Understanding the Water-in-Salt to Salt-in-Water Characteristics across the Zinc Chloride : Water Phase Diagram.

Using a series of time- and temperature-resolved synchrotron diffraction experiments, the relationship between multiple polymorphs of ZnCl2 and its respective hydrates is established. The δ-phase is found to be the pure anhydrous phase, while the α, β, and γ phases result from partial hydration. Diffraction, gravimetric, and calorimetric measurements across the entire ZnCl2·R H2O, 0 > R > ∞ composition range using ultrapure, doubly sublimed ZnCl2 establish the ZnCl2 : H2O phase diagram. The results are consistent with the existence of crystalline hydrates at R = 1.33, 3, and 4.5 and identify a mechanistic pathway for hydration. All water is not removed from hydrated ZnCl2 until the system is heated above its melting point. While hydration/dehydration is reversible in concentrated solutions, dehydration from dilute aqueous solutions can result in loss of HCl, the source of hydroxide impurities commonly found in commercial ZnCl2 preparations. The strong interaction between ZnCl2 and water exerts a significant impact on the solvent water such that the system exhibits a deep eutectic at a composition of about R = 7 (87.5 mol %) and a eutectic temperature below -60 °C.

Ammonia Mono Hydrate IV: An Attempted Structure Solution

The mixed homonuclear and heteronuclear hydrogen bonds in ammonia hydrates have been of interest for several decades. In this manuscript, a neutron powder diffraction study is presented to investigate the structure of ammonia monohydrate IV at 170 K at an elevated pressure of 3–5 GPa. The most plausible structure that accounts for all features in the experimental pattern was found in the P21/c space group and has the lattice parameters a=5.487(3) Å, b=19.068(4) Å, c=5.989(3) Å, and β=99.537(16) deg. While the data quality limits discussion to a proton-ordered structure, the structure presented here sheds light on an important part of the ammonia–water phase diagram.

Comparison of the phase transitions of high-pressure phases of ammonium fluoride and ice at ambient pressure

The phase diagrams of water and ammonium fluoride (NH4F) display some interesting parallels. Several crystalline NH4F phases have isostructural ice counterparts and one of the famous anomalies of water, the fact that the liquid is denser than ice Ih, is also found for NH4F. Here, we investigate the phase transitions of the pressure-quenched high-pressure phases of NH4F upon heating at ambient pressure with x-ray diffraction and calorimetry, and we compare the results with the corresponding ices. NH4F II transforms to NH4F Isd, which is a stacking-disordered variant of the stable hexagonal NH4F Ih polymorph. Heating NH4F III gives a complex mixture of NH4F II and NH4F Isd, while some NH4F III remains initially. Complete conversion to NH4F Isd is achieved above ∼220 K. The NH4F II obtained from NH4F III persists to much higher temperatures compared to the corresponding pressure-quenched NH4F II. Quantification of the stacking disorder in NH4F Isd reveals a more sluggish conversion to NH4F Ih for NH4F Isd from NH4F III. In general, the presence of stress and strain in the samples appears to have pronounced effects on the phase transition temperatures. NH4F shows a complete lack of amorphous forms at low temperatures either upon low-temperature compression of NH4F Ih or heating NH4F III at ambient pressure. The amorphous forms of ice are often used to explain the anomalies of water. It will, therefore, be interesting to explore if liquid NH4F displays more water-like anomalies despite the apparent lack of amorphous forms at low temperatures.

Using coherent X-rays to follow dynamics in amorphous ices.

Amorphous solid water plays an important role in our overall understanding of water's phase diagram. X-ray scattering is an important tool for characterising the different states of water, and modern storage ring and XFEL facilities have opened up new pathways to simultaneously study structure and dynamics. Here, X-ray photon correlation spectroscopy (XPCS) was used to study the dynamics of high-density amorphous (HDA) ice upon heating. We follow the structural transition from HDA to low-density amorphous (LDA) ice, by using wide-angle X-ray scattering (WAXS), for different heating rates. We used a new type of sample preparation, which allowed us to study μm-sized ice layers rather than powdered bulk samples. The study focuses on the non-equilibrium dynamics during fast heating, spontaneous transformation and crystallization. Performing the XPCS study at ultra-small angle (USAXS) geometry allows us to characterize the transition dynamics at length scales ranging from 60 nm-800 nm. For the HDA-LDA transition we observe a clear separation in three dynamical regimes, which show different dynamical crossovers at different length scales. The crystallization from LDA, instead, is observed to appear homogenously throughout the studied length scales.

Calculation of a temperature-volume phase diagram of water to inform the study of isochoric freezing down to cryogenic temperatures.

Phase diagrams are integral to the application and interpretation of materials thermodynamics, and none is more ubiquitous than the common temperature–pressure diagram of water and its many icy phases. Inspired by recent advances in isochoric thermodynamics, we here employ a simple convex hull approach to efficiently calculate an updated temperature–volume phase diagram for water and five of its solid polymorphs from existing Helmholtz free energy data. We proceed to highlight fundamental similarities between this T–V diagram and conventional binary temperature–concentration (T–x) diagrams, provide the volume coordinates of a variety of three-phase invariant reactions (e.g. “confined” or “volumetric” eutectics, peritectics, etc.) that occur amongst the phases of pure water under isochoric or confined conditions, and calculate the phase fraction evolution of ice Ih with temperature along multiple isochores of interest to experimental isochoric freezing. This work provides a requisite baseline upon which to extend the study of isochoric freezing to cryogenic temperatures, with potential applications in thermodynamic metrology, cryovolcanism, and cryopreservation.

Thermodynamic Modeling of Multicomponent Rare Earth Nitrates Aqueous Systems

Solubility constants of rare earth (RE) nitrates crystalline hydrates are determined in a wide temperature range (−30 to 120°C), salts solubilities and phase diagrams of water–RE nitrate systems are calculated. For multicomponent (n > 5) solutions of RE nitrates the assessment of solution properties as well as phase diagrams are shown to be feasible within experimental uncertainty. In case of mixtures of RE nitrates with similar hydrodynamic radii of ions, the parameters of RE1–RE2 interparticle interaction can be ignored without losing accuracy of thermodynamic modeling.

Structure and properties of two superionic ice phases

In the phase diagram of water, superionic ices with highly mobile protons within the stable oxygen sublattice have been predicted at high pressures. However, the existence of superionic ices and the location of the melting line have been challenging to determine from both theory and experiments, yielding contradictory results depending on the employed techniques and the interpretation of the data. Here we report high-pressure and high-temperature synchrotron X-ray diffraction and optical spectroscopy measurements of water in a laser-heated diamond anvil cell and reveal first-order phase transitions to ices with body-centred and face-centred cubic oxygen lattices. Based on the distinct density, increased optical conductivity and the greatly decreased fusion enthalpies, we assign these observed structures to the theoretically predicted superionic ice phases. Our measurements determine the pressure–temperature stability fields of superionic ice phases and the melting line, suggesting the presence of face-centred cubic superionic ice in water-rich giant planets, such as Neptune and Uranus. The melting line determined here is at higher temperatures than previously determined in static compression experiments, but it is in agreement with theoretical calculations and data from shock-wave experiments.

The influence of equation of state on impact dynamics between Pluto-like bodies

Impacts between planetary-sized bodies can explain the origin of satellites orbiting large (R>500 km) trans-Neptunian objects. Their water rich composition, along with the complex phase diagram of water, make it important to accurately model the wide range of thermodynamic conditions material experiences during an impact event and in the debris disk. Since differences in the thermodynamics may influence the system dynamics, we seek to evaluate how the choice of an equation of state (EOS) alters the system’s evolution. Specifically, we compare two EOSs that are constructed by different approaches: either by a simplified analytic description (Tillotson), or by interpolation of tabulated data (Sesame). Approximately 50 pairs of Smoothed Particle Hydrodynamics impact simulations were performed, with similar initial conditions but different EOSs, in the parameter space in which the Pluto–Charon binary is thought to form (slow impacts between Pluto-size, water rich bodies). Generally, we show that impact outcomes (e.g., circumplanetary debris disk) are consistent between EOSs. Some differences arise, importantly in the production of satellitesimals (large intact clumps) that form in the post-impact debris disk. When utilizing an analytic EOS, the emergence of satellitesimals is highly certain, while when using the tabulated EOS it is less common. This is because for the typical densities and energies experienced in these impacts, the analytic EOS predicts very low pressure values, leading to particles artificially aggregating by a tensile instability.

Liquid–liquid phase transition in simulations of ultrafast heating and decompression of amorphous ice

• Ultrafast heating experiments on amorphous ice clarified by simulations. • High density amorphous ice heated to liquid state by ultrafast laser pulse. • Decompression of high density liquid reveals liquid–liquid transition. • Simulations detect structural transition along out-of-equilibrium paths. A recent experiment [K. H. Kim, et al. , Science 370 , 978 (2020)] showed that it may be possible to detect a liquid–liquid phase transition (LLPT) in supercooled water by subjecting high density amorphous ice (HDA) to ultrafast heating, after which the sample reportedly undergoes spontaneous decompression from a high density liquid (HDL) to a low density liquid (LDL) via a first-order phase transition. Here we conduct computer simulations of the ST2 water model, in which a LLPT is known to occur. We subject various HDA samples of this model to a heating and decompression protocol that follows a thermodynamic pathway similar to that of the recent experiments. Our results show that a signature of the underlying equilibrium LLPT can be observed in a strongly out-of-equilibrium process that follows this pathway despite the very high heating and decompression rates employed here. Our results are also consistent with the phase diagram of glassy ST2 water reported in previous studies.

Influence of Liquid Inclusions to Explosive Instability of Ice

The influence of the nuclei of the liquid phase arising during mechanical deformations of polycrystalline ice at temperatures below -40 ... -45 C on its explosive instability is considered. The nucleus of the liquid phase appear in ice when part of the hydrogen bonds are broken when high pressure is applied to ice crystals. The resulting clusters can have characteristics close to those of bulk metastable water. It is known that such water in the region of negative temperatures has anomalous thermodynamic characteristics. In particular, at a temperature of -60 C and a pressure of 100 MPa, there is a second critical point of water for the liquid-liquid transition. It was found that the transition occurs between the two types of water LDL (low density water) and HDL (high density water), with the Widom line coming out into the one-component region of the water phase diagram. This line is the locus of increased fluctuations in entropy and density. Near atmospheric pressure, the temperature on the Widom line is -45 C. If the pressure inside the ice and its temperature turn out to be close to the line of coexistence of LDL and HDL, then liquid inhomogeneities can become a source of mechanical instability of the medium due to the growth of fluctuations in the energy of molecules and destruction of the ice structure. Such conditions can occur at temperatures below -45 C and pressures above 100 MPa.

The key to surfactant-free microemulsion demulsification: CO2 promotes the transfer of amphiphilic solvent to aqueous phase

In recent years, research on surfactant-free microemulsion (SFME) has given us new insight into the field of microemulsion. Here, we report a SFME with CO2 responsiveness prepared by mixing 1-dodecanol (oil phase), aqueous phase and N,N-dimethylethanolamine (DMEA, amphiphilic solvent) at appropriate proportion. The proportion of the three components used to prepare SFME was obtained by analyzing the ternary phase diagram of DMEA, 1-dodecanol and water. Meanwhile, the microstructure transition characteristics of SFME from oil-in-water (O/W) to bicontinuous phase (B.C.) to water-in-oil (W/O) was characterized by electrical conductivity and UV–Vis spectroscopy. In addition, the CO2 response behavior of W/O microemulsion has been studied deeply. We found that a significant demulsification phenomenon when CO2 was introduced into this SFME system. By measuring the concentration of DMEA in 1-dodecanol after demulsification, the demulsification mechanism of SFME can be confirmed: The introduction of CO2 causes the protonation of DMEA, and this process makes the amphiphilic solvent more soluble in the aqueous phase, which results in destabilization of this ternary system. Eventually, with the continuous introduction of CO2, the separation of the oil and water phases of SFME occurs.

Examining the Temperature Dependence of Louche Formation in Absinthe.

Absinthe is an anise-flavored alcohol that is typically served by adding cold water to form a cloudy green louche, similar to the cloudy white louche of ouzo. This microemulsion formation, due to the competing interactions within the oil–alcohol–water system, has been termed the ouzo effect. Previous work has examined the ternary oil–alcohol–water phase diagram in ouzo and limoncello. Additional work has also characterized the droplet size and stability of microemulsions in ouzo, limoncello, and pastis. However, less work has been done to examine the effect of temperature on louche formation despite the fact that the louche is traditionally formed by adding ice cold water. This work demonstrates that both the maximum turbidity and the fraction of alcohol at maximum turbidity are temperature-dependent. The louche formation can be fit with a logistic curve, and the resulting fit parameters are linear with temperature. Optical images show that the increased turbidity correlates with an increase in the number of droplets in the microemulsion.

Vapor-liquid equilibrium of water with the MB-pol many-body potential.

Among the many existing molecular models of water, the MB-pol many-body potential has emerged as a remarkably accurate model, capable of reproducing thermodynamic, structural, and dynamic properties across water's solid, liquid, and vapor phases. In this work, we assessed the performance of MB-pol with respect to an important set of properties related to vapor-liquid coexistence and interfacial behavior. Through direct coexistence classical molecular dynamics simulations at temperatures of 400K < T < 600K, we calculated properties such as equilibrium coexistence densities, vapor-liquid interfacial tension, vapor pressure, and enthalpy of vaporization and compared the MB-pol results to experimental data. We also compared rigid vs fully flexible variants of the MB-pol model and evaluated system size effects for the properties studied. We found that the MB-pol model predictions are in good agreement with experimental data, even for temperatures approaching the vapor-liquid critical point; this agreement was largely insensitive to system sizes or the rigid vs flexible treatment of the intramolecular degrees of freedom. These results attest to the chemical accuracy of MB-pol and its high degree of transferability, thus enabling MB-pol's application across a large swath of water's phase diagram.

Effect of ammonium fluoride doping on the ice III to ice IX phase transition.

Ice III is a hydrogen-disordered phase of ice that is stable between about 0.2 and 0.35 GPa. Upon cooling, it transforms to its hydrogen-ordered counterpart ice IX within the stability region of ice II. Here, the effect of ammonium fluoride doping on this phase transition is investigated, which is followed for the first time with in situ neutron diffraction. The a and c lattice constants are found to expand and contract, respectively, upon hydrogen ordering, yielding an overall negative volume change. Interestingly, the anisotropy in the lattice constants persists when ice IX is fully formed, and negative thermal expansion is observed. Analogous to the isostructural keatite and β-spodumenes, the negative thermal expansion can be explained through the buildup of torsional strain within the a-b plane as the helical "springs" within the structure expand upon heating. The reversibility of the phase transition was demonstrated upon heating. As seen in diffraction and Raman spectroscopy, the ammonium fluoride doping induces additional residual hydrogen disorder in ice IX and is suggested to be a chemical way for the "excitation" of the configurational ice-rules manifold. Compared to ice VIII, the dopant-induced hydrogen disorder in ice IX is smaller, which suggests a higher density of accessible configurational states close to the ground state in ice IX. This study highlights the importance of dopants for exploring the water's phase diagram and underpins the highly complex solid-state chemistry of ice.

Structure and dynamics of water plastic crystals from computer simulations.

Water has a rich phase diagram with several crystals, as confirmed by experiments. High-pressure and high-temperature water is of interest for Earth's mantle and exoplanetary investigations. It is in this region of the phase diagram of water that new plastic crystal phases of water have been revealed via computer simulations by both classical forcefields and ab initio calculations. However, these plastic phases still remain elusive in experiments. Here, we present a complete characterization of the structure, dynamics, and thermodynamics of the computational plastic crystal phases of water using molecular dynamics and the two-phase thermodynamic method and uncover the interplay between them. The relaxation times of different reorientational correlation functions are obtained for the hypothetical body-centered-cubic and face-centered-cubic plastic crystal phases of water at T = 440 K and P = 8 GPa. Results are compared to a high pressure liquid and ice VII phases to improve the understanding of the plastic crystal phases. Entropy results indicate that the fcc crystal is more stable compared to the bcc structure under the studied conditions.