Supercooled Liquid Phase Research Articles

Numerical method for computing the free energy of glasses.

We propose a numerical technique to compute the equilibrium free energy of glasses that cannot be prepared quasireversibly. For such systems, standard techniques for estimating the free energy by extrapolation cannot be used. Instead, we use a procedure that samples the equilibrium partition function of the basins of attraction of the different inherent structures (local potential energy minima) of the system. If all relevant inherent structures could be adequately sampled in the (supercooled) liquid phase, our approach would be rigorous. In any finite simulation, we will miss the lower-energy inherent structures that become dominant at very low temperatures. We find that our free energy estimates for a Kob-Andersen glass are lower than those obtained by very slow cooling, even at temperatures down to one-third of the glass transition temperature. The current approach could be applied to compute the chemical potential of ultrastable glassy materials and should enable the estimation of their solubility.

Some Aspects of the Liquid Water Thermodynamic Behavior: From The Stable to the Deep Supercooled Regime.

Liquid water is considered to be a peculiar example of glass forming materials because of the possibility of giving rise to amorphous phases with different densities and of the thermodynamic anomalies that characterize its supercooled liquid phase. In the present work, literature data on the density of bulk liquid water are analyzed in a wide temperature-pressure range, also including the glass phases. A careful data analysis, which was performed on different density isobars, made in terms of thermodynamic response functions, like the thermal expansion and the specific heat differences , proves, exclusively from the experimental data, the thermodynamic consistence of the liquid-liquid transition hypothesis. The study confirms that supercooled bulk water is a mixture of two liquid “phases”, namely the high density (HDL) and the low density (LDL) liquids that characterize different regions of the water phase diagram. Furthermore, the isobars behaviors clearly support the existence of both a liquid–liquid transition and of a liquid–liquid critical point.

Connection between liquid and non-crystalline solid phases in water.

The origin of water anomalies hides in an experimentally inaccessible region of the phase diagram known as no-man's land, bounded at low temperature by the domain of stability of amorphous glasses, and at high temperature by the homogeneous nucleation line, below which liquid water loses its metastability. The existence of at least two different forms of glass on one side, i.e., the low-density amorphous (LDA) and the high-density amorphous (HDA) ices, and of one anomalous liquid on the other side, points to a hidden connection between these states, whose understanding has the potential to uncover what happens in no-man's land and shed light on the complex nature of water's behavior. Here, we develop a Neural Network scheme capable of discerning local structures beyond tetrahedrality. Applied over a wide region of the water's phase diagram, we show that the local structures that characterize both LDA and HDA amorphous phases are indeed embedded in the supercooled liquid phase. Remarkably, the rapid increase in the LDA-like population with supercooling occurs in the same temperature and pressure region where thermodynamic fluctuations are maximized, linking these structures with water's anomalies. At the same time, the population of HDA-like environments rapidly increases with pressure, becoming the majority component at high density. Our results show that both LDA and HDA are genuine glasses, and provide a microscopic connection between the non-equilibrium and equilibrium phase diagrams of water.

Electrically Controlled Lasing in Supercooled Liquid Crystal Blue Phase I Microdroplets

We have prepared the liquid crystal blue phase (BP) microdroplets emulsified in the glycerol environment and investigated their electro-optical properties upon the applied electric field. We showed...

Nucleation and Growth of the Supercooled Liquid Phase Control Glass Transition in Bulk Ultrastable Glasses.

We report the anomalous bulk transformation of vapor deposited stable glasses into the liquid state. The transformation proceeds through two competing parallel processes: partial rejuvenation of the stable glass and nucleation and growth of liquid patches within the glass. The kinetics of the transformation extracted from heat capacity curves after isothermal runs is dominated by the heterogeneous nucleation and growth process that initiates at preexisting seeds and propagates radially at a velocity proportional to the alpha relaxation time. Remarkably, the distance between the activation seeds is independent of temperature within experimental uncertainty and amounts to several micrometers, a value in close agreement with the crossover length for TPD glasses. We speculate the initiation sites for the transformation of the glass into the supercooled liquid are localized regions of lower stability (or density).

Structural transformations in solid and liquid n-butanol from FTIR spectroscopy

FTIR spectra of n-butanol were registered for temperatures from −100 °С to 40 °С during heating of the sample and from 40 °С to −170 °С during its cooling. Structural changes at phase transitions solid–liquid and liquid–solid were detected. At n-butanol cooling below the melting point the initial crystalline structure was not achieved. Instead of it, a super-cooled liquid or amorphous phase was obtained. Quantum-chemical simulation of 27 n-butanol rotational conformers were provided via ROCBS-QB3 method. According to the calculations, the most stable conformer is TG′t. Comparison of calculated in the anharmonic approximation IR spectra of possible monomers and dimers of n-butanol with experimentally registered spectra showed that there are no monomers and dimers in the studied sample, and the structure of n-butanol in the condensed state is formed by bigger clusters.

A thermal analysis study of melt-quenched Zn5Se95 chalcogenide glass

Thermal analysis of chalcogenide glass similar to other materials is of great importance in order to increase the knowledge about its phase transitions, thermal stability, etc. The current study reports on the thermal kinetics of melt-quenched Zn5Se95 chalcogenide glass using differential thermal analysis (DTA) techniques under non-isothermal conditions. The glass-forming ability (GFA) and the relation between the glass transition and onset crystallization temperatures are found to show a linear behavior. In addition, Moynihan et al. Kissinger’s, and other approaches of Johnson-Mehl-Avrami utilized to determine the activation energy of the amorphous-crystalline and glass transition. It is found that the glass transition process cannot be concluded in terms of single activation energy, and that variation with the extent of conversion was analyzed using various iso-conventional methods. Therefore, the observed change of the activation energy throughout the glass transition reveals that the transition from amorphous to the supercooled liquid phase of Zn5Se95 glass is a complex process. The crystallization process at different heating rates is simulated using the Málek method, and Šesták–Berggren SB(M,N) model, in which the SB model show fairly good matching with the experimental DTA data. Moreover; the fragility index is a measure of the GFA of Zn5Se95 chalcogenide glass, which has been estimated using the glass transitions and activation energy values. We have found that the fragility index of Zn5Se95 glass values in between ∼13 and 30, depending on the heating rate, revealing that the synthesized glass is a strong liquid with excellent GFA.

Structural and electronic properties of liquid, amorphous, and supercooled liquid phases of In2Te5 from first-principles.

In2Te5 is a stoichiometric compound in the In-Te system of interest for applications in phase change electronic memories and thermoelectrics. Here, we perform a computational study of the structural, dynamical, and electronic properties of the liquid, supercooled liquid, and amorphous phases of this compound by means of density functional molecular dynamics simulations. Models of the supercooled liquid and amorphous phases have been generated by quenching from the melt. The structure of the liquid phase is characterized by a mixture of defective octahedral and tetrahedral local environments of In atoms, while the amorphous phase displays a mostly tetrahedral local geometry for In atoms with corner and edge sharing tetrahedra similar to those found in the crystalline phases of the In2Te5, InTe, and In2Te3 compounds. Comparison with our previous results on liquid and amorphous In2Te3 and further data on the structural properties of liquid In2Te3 are also discussed. The analysis of the electronic properties highlights the opening of a mobility gap in In2Te5 at about 150 K below the liquidus temperature.

Nose Temperature and Anticorrelation between Recrystallization Kinetics and Molecular Relaxation Dynamics in Amorphous Morniflumate at High Pressure

We probe the dielectric response of the supercooled liquid phase of Morniflumate, a drug with anti-inflammatory and antipyretic properties, studying in particular the pressure and temperature dependence of the relaxation dynamics, glass transition temperature Tg, and recrystallization kinetics. Tg increases by roughly 20 K every 100 MPa at low applied pressure, where the ratio Tg/Tm has a constant value of ∼0.8 (Tm = melting point). Liquid Morniflumate displays two dielectric relaxations: the structural α relaxation associated with the collective reorientational motions, which become arrested at Tg, and a secondary relaxation likely corresponding to an intramolecular dynamics. The relaxation times of both processes scale approximately with the inverse reduced temperature Tg/T. Near room temperature and under an applied pressure of 50 MPa, supercooled Morniflumate recrystallizes in a characteristic time of few hours, with an Avrami exponent of 1.15. Under these conditions, the recrystallization rate is a nonmonotonic function of temperature, displaying a maximum at around 298 K, which can be taken to be the optimum crystal growth temperature Tnose. The β relaxation becomes kinetically frozen at ambient temperature under an applied hydrostatic pressure higher than 320 MPa, suggesting that the Morniflumate glass should be kinetically stable under these conditions.

IR Studies of Thermally Stimulated Structural Phase Transformations in Cryovacuum Condensates of Freon 134a

The method of cryovacuum condensation of thin gas films and, in particular, condensation involving the formation of glassy states, provides ample opportunities for precise control and maintenance of the formation conditions of studied samples. This has prompted researchers to formulate and address the question of the relationship between the formation conditions/structure of molecules and the degree of kinetic stability of cryocondensates, including organic glasses. This study focused on thin films of Freon 134a cryovacuum condensates condensed on a cooled metal substrate comprised of gas at deposition temperatures ranging from 16–100 K and gas phase pressures from 10–4 to 10–6 Torr. A comparison between the vibrational spectra of Freon 134a in the gas phase and in the cryocondensed state is provided. The results of IR spectrometric studies of cryovacuum condensates of Freon 134a (2.5 μm thick) in the frequency range 400–4200 cm–1 are presented. Based on the obtained spectra and data on their thermally stimulated transformations, an assumption is made that, in the temperature range 16–60 K, Freon 134a cryocondensates are in an amorphous state with different degrees of amorphization. At the vitrification temperature of 70 K, transition from the amorphous glassy state to the state of the supercooled liquid phase takes place, followed by its crystallization into the state of a plastic crystal. In the temperature range of 78–80 K, the transition of a plastic crystal to a crystalline state with a monoclinic lattice begins.

Effect of Si on the Microstructure and Performance of Ti-Cu-Zr-Ni-based Amorphous Filler Metal

(Ti0.46Cu0.14Zr0.27Ni0.13)-xSi (x=0, 0.5, 1, 2, wt%) amorphous filler metal was prepared by arc melting and fast-cooling melt-spinning techniques, and the effect of a certain amount of Si added to the filler metal on its amorphous forming ability was studied. The results show that the filler metal has the strongest amorphous forming ability when the content of Si reaches 0.5%; its wetting area is 3.06 cm2 its supercooled liquid phase region width ΔTx=56 °C, its reduced glass transition temperature Trg=0.5387, and its liquidus temperature (Tl) is 949 °C. The vacuum brazing was done for SiC and TC4 using this amorphous alloy as the filler metal, and the shear strength of brazed joint is 80 MPa. The amorphous forming ability of filler metal is improved with addition of Si to the filler metal.

Effect of Silicon on the Microstructure and Performance of the New Binary Deep Eutectic Ti–Cu–Zr–Ni-Based Filler Metal

This study designed (Ti0.55Cu0.20Zr0.15Ni0.10)1−xSix amorphous alloys based on binary deep eutectics and examined the effect of silicon (Si) on the amorphous forming ability of the filler alloys. The results show that a certain amount of Si added to the filler metals could improve the amorphous forming ability of the alloys. Under the same experimental conditions, the Ti0.55Cu0.20Zr0.15Ni0.10 filler metal with 0.5 wt % Si had the strongest amorphous forming ability compared to the other filler alloys containing different amounts of Si; its reduced glass transition temperature (Trg) was 0.5554, and its supercooled liquid phase region width (∆Tx) reached 60 °C. The (Ti0.55Cu0.20Zr0.15Ni0.10)99.5%Si0.5% filler metal designed in these experiments presented good amorphous forming ability and wettability. The brazed joint of SiC and TC4 obtained with this amorphous filler metal showed a shear strength of 102 MPa, indicating an increase of 122% compared to the brazed joint obtained with the filler metal without Si.

Direction of practical use in the power engineering of the phenomenon of electrochemical phase formation in metals and alloys via a supercooled liquid state stage

Purpose. The direction of practical use in power engineering of the discovered phenomenon of electrochemical phase formation in metals and alloys via a supercooled liquid state stage is required to determine. Methodology. The methods of scanning electron microscopy and impedance spectroscopy were used. Findings. The surface morphology and electrical properties of metallic (copper and nickel) foils obtained by the usual method of electrodeposition and the method of stimulated nucleation during solidification of a supercooled liquid phase of the metal being electrodeposited are studied. The effect of reducing the transient electrical resistance at the current lead / electrode interface has been established when using copper or nickel foil with a branched surface morphology as a current lead. The direction of practical use of the established phenomenon in the production of chemical sources of current is determined. Originality. The relationship between the surface morphology and the electrical properties of the metallic foil is revealed. Practical value. The obtained results open the prospect of manufacturing chemical current sources having increased power and stability.

Developing β-type bulk metallic glass composites from Ti/Zr-based bulk metallic glasses by an iteration method

Bulk metallic glass composites containing in-situ formed β-Ti/Zr phases (β-type BMGCs), which exhibit a good combination of strength and plasticity, were generally developed by adding β-stabilizers, such as Nb, Ta, V, etc., into Ti/Zr-based bulk metallic glasses (BMGs). In this work, an iteration method is proposed to develop β-type BMGCs from Ti/Zr-based BMGs, and the compositions of BMGCs can be designed by “the composition of in-situ formed β phase (the iterative variable) + the composition of BMG”. Due to the fast elemental diffusions between the β phase and the (supercooled) liquid phase, the iteration method can develop β-type BMGCs in which both phases can maintain a mutual (metastable) equilibrium during solidification. The procedures of the iteration method and its underlying thermodynamic and kinetic principles are discussed, and a Zr56.9Ti18.8Cu7.4Ni5.7Be11.3 BMGC was developed from Vitreloy 1 by using the iterative method. As compared with β-type BMGCs developed by the conventional method, β-type BMGCs developed by the iteration method have two advantages: (i) the good glass-forming ability of the initial BMGs can be largely inherited by the glassy matrices in BMGCs; (ii) without adding β-stabilizers, the in-situ formed β phases are more likely to be metastable. The current iteration method is of scientific significance on improving plasticity of Ti/Zr-based BMGs and developing new β-type BMGCs.

Dielectric relaxation studies in super-cooled liquid and glassy phases of anti-cancerous alkaloid: Brucine

Brucine has good anti-tumor effects, on both liver cancer and breast cancer. It has bioavailability of 40.83%. Since the bioavailability of the drug is low, an alternative method to increase its bioavailability and solubility is by changing the drug into glassy form. We used Differential Scanning Calorimetry (DSC) for studying the glass forming ability of the drug. Brucine was found to be a very good glass former glass transition temperature 365 K. Based on the DSC analysis we have used broadband dielectric spectroscopy (BDS) for studying the drug in the super cooled and glassy state. BDS is an effective tool to probe the molecular dynamics in the super cooled and glassy state. Molecular mobility is found to be present even in the glassy state of this active pharmaceutical ingredient (API) which is responsible for the instability. Our aim is to study the factors responsible for instability of this API in amorphous form. Cooling curves for dielectric permittivity and dielectric loss revealed the presence of structural (α) and secondary relaxations (β and γ). Temperature dependence of relaxation time is fitted by Vogel–Fulcher–Tammann equation and found the values of activation energy of the α relaxation, fragility and glass transition temperature. Paluch’s anti correlation is also verified, that the width of the α-loss peak at or near the glass transition temperature Tg is strongly anticorrelated with the polarity of the molecule. The larger the dielectric relaxation strength Δe (Tg) of the system, the narrower is the α-loss peak (higher value of βKWW).

Scaling of dielectric response of supercooled disordered phases

ABSTRACTA generalised scaling relationship of the imaginary part of the dielectric permittivity as well as of the real part of the dielectric permittivity is presented. The proposed scaling of the dielectric response has been successfully applied to main relaxation processes in various supercooled isotropic liquid phases and supercooled plastic-crystal phases in several glass-forming liquids as glycerol, propylene carbonate, 3-fluoroaniline, ethanol, cyclooctanol and cyanocyclohexane. Existence of the excess wing, the resolved secondary relaxation (β-relaxation) or both the processes was identified for some of these materials. It is demonstrated that behaviour of the resolved β-relaxation and the excess wing strictly depends on the parameters of the main relaxation process. This implies that the main relaxation process and the secondary one are not independent.

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

The microphysics of clouds over the Antarctic Peninsula – Part 2: modelling aspects within Polar WRF

Abstract. The first intercomparisons of cloud microphysics schemes implemented in the Weather Research and Forecasting (WRF) mesoscale atmospheric model (version 3.5.1) are performed on the Antarctic Peninsula using the polar version of WRF (Polar WRF) at 5 km resolution, along with comparisons to the British Antarctic Survey's aircraft measurements (presented in part 1 of this work; Lachlan-Cope et al., 2016). This study follows previous works suggesting the misrepresentation of the cloud thermodynamic phase in order to explain large radiative biases derived at the surface in Polar WRF continent-wide (at 15 km or coarser horizontal resolution) and in the Polar WRF-based operational forecast model Antarctic Mesoscale Prediction System (AMPS) over the Larsen C Ice Shelf at 5 km horizontal resolution. Five cloud microphysics schemes are investigated: the WRF single-moment five-class scheme (WSM5), the WRF double-moment six-class scheme (WDM6), the Morrison double-moment scheme, the Thompson scheme, and the Milbrandt–Yau double-moment seven-class scheme. WSM5 (used in AMPS) and WDM6 (an upgrade version of WSM5) lead to the largest biases in observed supercooled liquid phase and surface radiative biases. The schemes simulating clouds in closest agreement to the observations are the Morrison, Thompson, and Milbrandt schemes for their better average prediction of occurrences of clouds and cloud phase. Interestingly, those three schemes are also the ones allowing for significant reduction of the longwave surface radiative bias over the Larsen C Ice Shelf (eastern side of the peninsula). This is important for surface energy budget consideration with Polar WRF since the cloud radiative effect is more pronounced in the infrared over icy surfaces. Overall, the Morrison scheme compares better to the cloud observation and radiation measurements. The fact that WSM5 and WDM6 are single-moment parameterizations for the ice crystals is responsible for their lesser ability to model the supercooled liquid clouds compared to the other schemes. However, our investigation shows that all the schemes fail at simulating the supercooled liquid mass at some temperatures (altitudes) where observations show evidence of its persistence. An ice nuclei parameterization relying on both temperature and aerosol content like DeMott et al. (2010) (not currently used in WRF cloud schemes) is in best agreement with the observations, at temperatures and aerosol concentration characteristic of the Antarctic Peninsula where the primary ice production occurs (part 1), compared to parameterization only relying on the atmospheric temperature (used by the WRF cloud schemes). Overall, a realistic double-moment ice microphysics implementation is needed for the correct representation of the supercooled liquid phase in Antarctic clouds. Moreover, a more realistic ice-nucleating particle alone is not enough to improve the cloud modelling, and water vapour and temperature biases also need to be further investigated and reduced.

Relaxation dynamics in pyrrolidinium based ionic liquids: The role of the anion conformers

We report density functional theory (DFT) calculations and low-frequency mechanical spectroscopy results on two ionic liquids having the same N-butyl-N-methyl-pyrrolidinium cation (PYR14), but different anions, (nonafluorobutanesulfonyl)(toluenesulfonyl)imide (IMT4) and 1,3 hexafluoropropane-disulfonylimide (IM3), belonging to the per(fluoroalkylsulfonyl)imide family. For both samples, a relaxation process is observed in their supercooled liquid phase, which can be described by a hopping model between non-equivalent configurations. In agreement with previous results, the relaxation is attributed to the ions motion. The comparison among calculations of the anion conformers population and the analysis of the experimental data points out that the non-equivalent configurations between which the ion motion occurs involve a different configuration for the anion.

Dynamics of supercooled liquid and plastic crystalline ethanol: Dielectric relaxation and AC nanocalorimetry distinguish structural α- and Debye relaxation processes.

Physical vapor deposition has been used to prepare glasses of ethanol. Upon heating, the glasses transformed into the supercooled liquid phase and then crystallized into the plastic crystal phase. The dynamic glass transition of the supercooled liquid is successfully measured by AC nanocalorimetry, and preliminary results for the plastic crystal are obtained. The frequency dependences of these dynamic glass transitions observed by AC nanocalorimetry are in disagreement with conclusions from previously published dielectric spectra of ethanol. Existing dielectric loss spectra have been carefully re-evaluated considering a Debye peak, which is a typical feature in the dielectric loss spectra of monohydroxy alcohols. The re-evaluated dielectric fits reveal a prominent dielectric Debye peak, a smaller and asymmetrically broadened peak, which is identified as the signature of the structural α-relaxation and a Johari-Goldstein secondary relaxation process. This new assignment of the dielectric processes is supported by the observation that the AC nanocalorimetry dynamic glass transition temperature, Tα, coincides with the dielectric structural α-relaxation process rather than the Debye process. The combined results from dielectric spectroscopy and AC nanocalorimetry on the plastic crystal of ethanol suggest the occurrence of a Debye process also in the plastic crystal phase.