High-density Liquid Research Articles

Liquid-liquid transition and critical point in sulfur.

The liquid-liquid transition (LLT), in which a single-component liquid transforms into another one via a first-order phase transition, is an intriguing phenomenon that has changed our perception of the liquid state. LLTs have been predicted from computer simulations of water1,2, silicon3, carbon dioxide4, carbon5, hydrogen6 and nitrogen7. Experimental evidence has been found mostly in supercooled (that is, metastable) liquids such as Y2O3-Al2O3 mixtures8, water9 and other molecular liquids10-12. However, the LLT in supercooled liquids often occurs simultaneously with crystallization, making it difficult to separate the two phenomena13. A liquid-liquid critical point (LLCP), similar to the gas-liquid critical point, has been predicted at the end of the LLT line that separates the low- and high-density liquids in some cases, but has not yet been experimentally observed for any materials. This putative LLCP has been invoked to explain the thermodynamic anomalies of water1. Here we report combined in situ density, X-ray diffraction and Raman scattering measurements that provide direct evidence for a first-order LLT and an LLCP in sulfur. The transformation manifests itself as a sharp density jump between the low- and high-density liquids and by distinct features in the pair distribution function. We observe a non-monotonic variation of the density jump with increasing temperature: it first increases and then decreases when moving away from the critical point. This behaviour is linked to the competing effects of density and entropy in driving the transition. The existence of a first-order LLT and a critical point in sulfur could provide insight into the anomalous behaviour of important liquids such as water.

Synthesis and properties of high-energy-density hydrocarbons based on 5-vinyl-2-norbornene

A norbornane derivative, exo-tetrahydrodicyclopentadiene, is the main component of the high-density liquid fuel called JP-10. In the current communication we describe the preparation of some related norbornane-containing hydrocarbons and their energetic properties. The desired hydrocarbons were readily obtained in high yields using Diels-Alder and/or cyclopropanation reactions from the industrially available 5-vinyl-2-norbornene. As a result, the hydrocarbons containing two norbornane moieties or norbornyl and cyclopropyl groups were prepared. The heats of combustion, densities and freezing points of the prepared norbornane derivatives were evaluated. High densities in the range of 0.856–0.977 g/cm3 and low freezing points (below −60 °C) were found for the obtained hydrocarbons. By altering the structure of such a hydrocarbons, the energy density as high as 41.24 MJ/L was achieved. The energy densities for the hydrocarbons consisting of two norbornane moieties or norbornyl and cyclopropyl fragments were noticeably higher than that of JP-10. Taking into account the low freezing points, high densities and high energy densities, the developed norbornane-type hydrocarbons can be considered as a promising components for high-energy density liquid propellants.

Unraveling liquid polymorphism in silicon driven out-of-equilibrium.

Using nonequilibrium molecular dynamics simulations, we study the properties of supercooled liquids of Si under shear at T = 1060 K over a range of densities encompassing the low-density liquid (LDL) and high-density liquid (HDL) forms. This enables us to generate nonequilibrium steady-states of the LDL and HDL polymorphs that remain stabilized in their liquid forms for as long as the shear is applied. This is unlike the LDL and HDL forms at rest, which are metastable under those conditions and, when at rest, rapidly undergo a transition toward the crystal, i.e., the thermodynamically stable equilibrium phase. In particular, through a detailed analysis of the structural and energetic features of the liquids under shear, we identify the range of densities, as well as the range of shear rates, which give rise to the two forms. We also show how the competition between shear and tetrahedral order impacts the two-body entropy in steady-states of Si under shear. These results open the door to new ways of utilizing shear to stabilize forms that are metastable at rest and can exhibit unique properties, since, for instance, experiments on Si have shown that HDL is metallic with no bandgap, while LDL is semimetallic with a pseudogap.

Conversion of agricultural waste into stable biocrude using spinel oxide catalysts

Biomass, the feedstock for biocrude and ultimately renewable diesel is a low energy density feedstock. The transport of this feedstock over long distance has been proven to be a major burden on the commercialisation of biorefining. Therefore, it has been generally accepted that biomass should be upgraded to biocrude (a relatively high energy density liquid) in close proximity to the biomass sources. The biocrude liquid would then be transported to a biorefinery. Biocrude contains large amounts of oxygen (generally up to 38 wt%) that is removed from the crude in the refining process. In this study, we have synthesised a range of spinel oxide based catalysts to remove oxygen from the biocrude during the catalytic fast pyrolysis. The activity of spinel oxide (MgB2O4 where B = Fe, Al, Cr, Ga, La, Y, In) catalysts were screened for the pyrolysis reaction. While all the tested spinel oxides deoxygenated the pyrolysis vapour, MgCr2O4 was found to be effective in terms of oxygen removal efficiency relative to the quantity of bio oil produced.

High-Density Liquid Water at a Water-Ice Interface.

Because ice surfaces catalyze various key chemical reactions impacting nature and human life, the structure and dynamics of interfacial layers between water vapor and ice have been extensively debated with attention to the quasi-liquid layer. Other interfaces between liquid water and ice remain relatively underexplored, despite their importance and abundance on the Earth and icy extraterrestrial bodies. By in situ optical microscopy, we found that a high-density liquid layer, distinguishable from bulk water, formed at the interface between water and high-pressure ice III or VI, when they were grown or melted in a sapphire anvil cell. The liquid layer showed a bicontinuous pattern, indicating that immiscible waters with distinct structures were separated on the interfaces in a similar manner to liquid-liquid phase separation through spinodal decomposition. Our observations not only provide a novel opportunity to explore ice surfaces but also give insight into the two kinds of structured water.

A computational study of excess properties for mW potential model of water in supercooled region

In this work, we studied the liquid–crystal transition of water using monatomic potential model (mW) (Molinero and Moore, 2009). To simulate water, the NPT-MC simulation were performed and obtained the average properties as potential energy (〈ϕ′〉) and density (〈ρ〉) at various temperatures which are in the very good agreement (i.e. 〈ϕ′〉=−1.766 and 〈ρ〉=0.448 at 202 K) with the literature values (Hujo et al., 2011). The free energy difference between the two liquid phases of water was computed by thermodynamic integration along with a reversible path at zero pressure and various temperatures. The recently developed thermodynamic integration (TDI) method was used to computed the excess Gibbs free energy of high density liquid (HDL) phase with respect to the crystalline phase at different temperatures in the supercooled region of mW-water model (Molinero and Moore, 2009). Based on the slope of excess Gibbs free energy with respect to temperature the excess entropy of the high density liquid (HDL) phase was obtained, which shows an anomalous behavior at or near the liquid–liquid transition temperature of Tll=202 K (Molinero and Moore, 2009). The excess entropy of the liquid phase in the supercooled mW water shows a sharp decline at or near the liquid–liquid phase transition temperature (Tll). The excess entropy of the HDL phase decreases as the temperature decreases to 197 K and increases at 192 K. Our results are in good agreement with the previous observation of a anomalous dependency of the density on temperature in MD simulations starting in the HDL phase at a temperature just above Tll (Moore and Molinero, 2009).

Instantaneous normal mode analysis for OKE reduced spectra of liquid and supercooled water: Contributions of low-density and high-density liquids

In this paper, we investigated the optical Kerr effect (OKE) reduced spectral density (RSD) of liquid and supercooled water at ambient pressure and focused on the contributions of low-density liquid (LDL) and high-density liquid (HDL), which local structures are characterized with tetrahedral order and disorder, respectively. The water systems were generated by performing molecular dynamics (MD) simulations with TIP4P/2005 force fields, and molecules were classified into LDL and HDL with the microscopic structural descriptor [Nature commun. 3 (2014) 3556.]. The OKE RSD was calculated with a model involving the intrinsic polarizabilities of individual molecules and the dipole-induced-dipole mechanism between them. The instantaneous normal mode (INM) analysis was used to dissect the OKE RSD obtained by MD simulations. By considering water as a mixture of LDL and HDL, the OKE RSD in the linearized INM theory is a sum of three contributions, which are resulted from the two partial liquids individually and a cross correlation associated with both of them, in a formulism similar as that for the static structure factor of a binary mixture. By exploring with two separation schemes on the collective polarizability, where they are complemental to each other, the INM analysis provides an insight into the physical causes for the bands in the OKE RSD of liquid and supercooled water and the relation of each band to the local structures of LDL and HDL.

497 Multimodality imaging of an evergreen conundrum: true or false aneurysm of the left ventricle?

Abstract In case of transmural necrosis following STEMI, the myocardial wall may develop a true or false aneurysm. While the former usually has a benign course, the latter has a propensity to rupture leading to an ominous prognosis. We report the case of a patient with a recent inferior STEMI complicated with LV aneurysm of the inferior wall, initially diagnosed as a false aneurysm. We describe the case of a 77-year-old man affected by hypertension, diabetes and AF. Two months before he experienced an inferior STEMI treated with late (>12 hours from symptoms onset) pPCI and implantation of a DES on the RCA and the postero-lateral branch. TTE showed a mildly reduced LV systolic function (EF 50%) due to akinesia of the inferior wall. The patient presented to the ED for recurrent syncopes at rest. Vital signs were unremarkable. Troponin and electrolytes were within normal range. ECG showed a normofrequent sinus rhythm and Q waves with persistent ST elevation in the inferior leads. TTE showed a suspected rupture of the inferior wall in the middle segment between the posterolateral papillary muscle and the mitral annulus. The rupture seemed to be contained by the pericardium so as to create a huge cavity communicating with the LV through an apparently small neck and refurnished with turbolent blood during the cardiac cycle. In the suspicion of a pseudoaneurysm ( an urgent cardiac CT was performed. CT showed an extraventricular cavity apparently contained by the pericardium with a narrow neck and a pericardial effusion of a high density liquid. A diagnosis of post-infarction pseudoaneurysm was made. The day after the patient was stable but TTE showed a mild increase of the size of the "pseudoaneurysm", hence the Heart Team referred the patient to the cardiac surgery department for an urgent repair. In the surgical room TOE displayed the large cavity rising from the inferior wall of the LV and the communication thorugh a large neck. The intraoperatory finding was, unexpectedly, a true aneurysm of the inferior wall. The redundant aneurysm was excised and the defect was succesfully closed with a bovine pericardium patch. No periprocedural complication was recorded and the postoperatory period was uneventful. The present case strikingly shows how a mechanical complication may develop in spite of myocardial revascularization. The high level of suspicion led to a strong effort to achieve a definite diagnosis. Multimodality imaging plays a pivotal role and is warranted since the initial evaluation with TTE may be inconclusive. CT has a high diagnostic yield but false positives may happen. MRI could have been more specific in our case, but the clinical evolution and the CT images led us to be confident in referring the patient to an urgent cardiac surgery. In conclusion, the non invasive differential diagnosis between true and false aneurysm still remains a modern challenge. Abstract 497 Figure. Multimodality imaging of a LV aneurysm

Homogeneous nucleation of phase transformations in supercooled water

The classical nucleation equation, applied to two liquids, is completed by an additional enthalpy for solid supercluster formation governing the liquid and glass transformations. This model defines a formation rule of glacial phases, explaining the origin of the first-order transition of water from fragile-to-strong liquids at TLL = 228.5 K, only fixing Tg = 137.1 K. All thermodynamic properties and transitions, even under pressure P, are now predicted in agreement with experiments. The lowest-density liquid is, at once, the glacial phase of fragile and high-density liquids. It is formed at TLL, remains liquid during the first cooling, and gives rise to the glass Phase 3 by heating through a first-order transition without latent heat at TK2 = 122.4 K. Medium-range order appears above Tg during the first heating. Phase 3 with its own Kauzmann temperature undergoes the first-order transition at TLL without latent heat and superheats up to Tn+ > Tm.

Real-space visualization of intercalated water phases at the hydrophobic graphene interface with atomic force microscopy

The phase behavior of water is a topic of perpetual interest due to its remarkable anomalous properties and importance to biology, material science, geoscience, nanoscience, etc. It is predicted confined water at interface can exist in large amounts of crystalline or amorphous states. However, the experimental evidence of coexistence of liquid water phases at interface is still insufficient. Here, a special folding few-layers graphene film was elaborate prepared to form a hydrophobic/hydrophobic interface, which can provide a suited platform to study the structure and properties of confined liquid water. The real-space visualization of intercalated water layers phases at the folding interface is obtained using advanced atomic force microscopy (AFM). The folding graphene interface displays complicated internal interfacial characteristics. The intercalated water molecules present themselves as two phases, low-density liquid (LDL, solid-like) and high-density liquid (HDL, liquid-like), according to their specific mechanical properties taken in two multifrequency-AFM (MF-AFM) modes. Furthermore, the water molecules structural evolution is demonstrated in a series of continuous MF-AFM measurements. The work preliminary confirms the existence of two liquid phases of water in real space and will inspire further experimental work to deeply understanding their liquid dynamics behavior.

Microbial consortia including methanotrophs: some benefits of living together.

With the progress of biotechnological research and improvements made in bioprocessing with pure cultures, microbial consortia have gained recognition for accomplishing biological processes with improved effectiveness. Microbes are indispensable tool in developing bioprocesses for the production of bioenergy and biochemicals while utilizing renewable resources due to technical, economic and environmental advantages. They communicate with specific cohorts in close proximity to promote metabolic cooperation. Use of positive microbial associations has been recognized widely, especially in food industries and bioremediation of toxic compounds and waste materials. Role of microbial associations in developing sustainable energy sources and substitutes for conventional fuels is highly promising with many commercial prospects. Detoxification of chemical contaminants sourced from domestic, agricultural and industrial wastes has also been achieved through microbial catalysis in pure and co-culture systems. Methanotrophs, the sole biological sink of greenhouse gas methane, catalyze the methane monooxygenasemediated oxidation of methane to methanol, a high energy density liquid and key platform chemical to produce commodity chemical compounds and their derivatives. Constructed microbial consortia have positive effects, such as improved biomass, biocatalytic potential, stability etc. In a methanotroph-heterotroph consortium, non-methanotrophs provide key nutrient factors and alleviate the toxicity from the culture. Non-methanotrophic organisms biologically stimulate the growth and activity of methanotrophs via production of growth stimulators. However, methanotrophs in association with co-cultured microorganisms are in need of further exploration and thorough investigation to study their interaction mode and application with improved effectiveness.

Evaluation of equations of state in multiphase lattice Boltzmann method with considering surface wettability effects

A two-dimensional lattice Boltzmann method (LBM) is applied to investigate the use of various equations of state (EoS) for the simulation of liquid–vapor two-phase flow systems with considering the wetting properties, namely the hydrophilic and hydrophobic characteristics, for solid surfaces. The pseudo-potential single-component multiphase Shan–Chen model is used to resolve inter-particle interactions and phase change between the liquid and its vapor. Several EoSs, including the Redlich–Kwong (R–K), Carnahan-Starling (C–S), and Peng–Robinson (P–R) in comparison with the Shan–Chen (S–C) model are considered to study their effects on the numerical simulation results in terms of density ratios, spurious velocities and the contact angle of the two-phase flow with the solid wall. Accuracy and performance of the multiphase LBM by incorporating various EoSs are examined by solving two-phase flow systems at different conditions. Herein, three test cases considered are an equilibrium state of a droplet suspended in the vapor phase, a liquid droplet located on the solid surface, and a liquid droplet motion through a grooved channel with different wetting conditions. The results obtained demonstrate that implementation of the wall boundary condition with the wettability effects significantly impacts the numerical stability of the LBM with the EoSs employed for simulation of liquid–vapor flow problems, particularly at high-density ratio. Simulation of the equilibrium state of a droplet on a surface with considering wettability effects shows that the S–C model, R–K, P–R and C–S EoSs are stable for the maximum density ratio up to ρl∕ρv=74.6, 78.9, 4904.4 and 147, respectively. It is defined that the parasitic currents do not increase significantly due to imposing the wetting condition on the solid wall, however, the numerical solutions with considering wettability effects are more sensitive at high-density ratios. The present study demonstrates that the P–R EoS is more stable for simulation of high-density ratio liquid–vapor systems with reasonable spurious currents in the interfacial region for the flow problems with the periodic computational domain. However, with considering the wetting wall boundary condition, the C–S EoS produces less spurious velocity in the interface region, which leads to more precise and stable numerical simulations in comparison with the other EoSs applied for the equilibrium state of a liquid droplet on the solid surface. The results obtained also demonstrate the capability of the multiphase LBM for predicting practical flow characteristics with different EoSs implemented.

Development of Highly Durable Anion Conductive Membrane with All-Aromatic Backbone for Alkaline Fuel Cell Application

Introduction: Solid alkaline fuel cell using anion conductive membrane (ACM) attracts increasing attention since non-noble metal electrode catalyst and high density liquid fuel can be used in this system. However, development of chemically durable membrane is critical for practical device application. Currently, benzyl trimethylammonium modified polyarylene ethers (i.e. polyethersulfone, polyphenyleneoxide, polyetherketon) are used as typical aromatic ACMs for alkaline fuel cell application. However, aryl ether bond in the backbone is not stable and suffered from chain scission under alkaline environment [1], leading to a loss of mechanical strength and conductivity of the membrane For this sense, ACM consisting of only aromatic backbone such as polyphenylene ACM is potential candidate for highly durable membranes [2-4]. However, these membranes are usually suffered from low solubility because of the rigid linear backbone and strong intermolecular π-π interaction. This drawback results in the difficultly for processing membranes To overcome these problems, in this work, we have synthesized a novel ACM with all-aromatic backbone for alkaline fuel cell application. The designed polymer backbone is composed of alternative m-phenylene and p-phenylene unit, changing the polymer structure to 2D zigzag conformation to suppress strong intermolecular π-πstacking. (Fig 1). Also, branched alkyl side chain was introduced for further enhancing solubility. We expected that AEM with both high durability and solubility can be obtained by using this membrane. Method: The precursor polymer for target membrane was synthesized by Pd-catalyzed Suzuki-Miyaura polymerization between m-phenylene and p-phenylene derivatives [5]. Structure and molecular weight of this precursor polymer were evaluated by 1H-NMR and gel permeation chromatography (GPC). Bromide groups at the polymer side chain were reacted with trimethylamine to afford the target membrane. Ion exchange capacity (IEC) of the membrane was evaluated by both 1H-NMR and titration. Ion conductivity of the membrane was calculated by alternative current impedance measurement. Alkaline stability of this membrane was evaluated by comparing 1H-NMR spectra before and after soaking into 8M NaOH aq, at 80 oC. Results and Discussion: The number average molecular weight (Mn) and polydistersity (PDI) of the precursor polymer were Mn=18000 and PDI=1.6, respectively. Quaternization of the precursor polymer proceeded almost quantitatively from 1H-NMR spectra. IEC of target polymer was 2.6 meq from NMR analysis and similar value (2.4) was obtained in titration. The synthesized membrane can be dissolved well into methanol, dimethylsulfoxide.and also 1-propanol/water (1:1 vol) mixture, which is typically used as suitable solvent for membrane electrode assembly (MEA) preparation. This indicates that the developed polymer is also promising candidate for an ionomer of fuel cells. Bormide and bicarbonate conductivity of the membrane were 52 mS/cm and 41 mS/cm (70 oC, RH100%), respectively. The conductivity value is high enough for fuel cell application. Chemical stability of the developed membrane was evaluated in harsh alkaline condition (8M NaOH, 80 oC). Even after one week, no detectable change was observed in the membrane. In fact, 1H-NMR spectra of the membrane after the alkaline stability test shows that both the anion exchange group and the backbone are stable in this condition. These results indicate that the developed all-aromatic ACM is promising candidate for a membrane and an ionomer of alkaline fuel cell. Reference [1] S. Miyanishi, T. Yamaguchi, Phys. Chem. Chem. Phys., 2016,18, 12009-12023 [2] E. J. Park and Y. S. Kim, J. Mater. Chem. A, 2018, 6, 15456-15477 [3] S. Miyanishi, T. Yamaguchi, J. Mater. Chem. A, 2019,7, 2219-2224 [4] H. P. R. Graha, S. Ando, S. Miyanishi and T. Yamaguchi, Chem. Commun., 2018, 54, 10820–10823. [5] B. Deffner and A.D. Schluter, Poly. Chem. 2015, 6, 7833-7840 Figure 1

Order-disorder transition in a two-dimensional associating lattice gas.

We study an associating lattice gas (ALG) using Monte Carlo simulation on the triangular lattice and semianalytical solutions on Husimi lattices. In this model, the molecules have an orientational degree of freedom and the interactions depend on the relative orientations of nearest-neighbor molecules, mimicking the formation of hydrogen bonds. We focus on the transition between the high-density liquid (HDL) phase and the isotropic phase in the limit of full occupancy, corresponding to chemical potential μ→∞, which has not yet been studied systematically. Simulations yield a continuous phase transition at τ_{c}=k_{B}T_{c}/γ=0.4763(1) (where -γ is the bond energy) between the low-temperature HDL phase, with a nonvanishing mean orientation of the molecules, and the high-temperature isotropic phase. Results for critical exponents and the Binder cumulant indicate that the transition belongs to the three-state Potts model universality class, even though the ALG Hamiltonian does not have the full permutation symmetry of the Potts model. In contrast with simulation, the Husimi lattice analyses furnish a discontinuous phase transition, characterized by a discontinuity of the nematic order parameter. The transition temperatures (τ_{c}=0.51403 and 0.51207 for trees built with triangles and hexagons, respectively) are slightly higher than that found via simulation. Since the Husimi lattice studies show that the ALG phase diagram features a discontinuous isotropic-HDL line for finite μ, three possible scenarios arise for the triangular lattice. The first is that in the limit μ→∞ the first-order line ends in a critical point; the second is a change in the nature of the transition at some finite chemical potential; the third is that the entire line is one of continuous phase transitions. Results from other ALG models and the fact that mean-field approximations show a discontinuous phase transition for the three-state Potts model (known to possess a continuous transition) lends some weight to the third alternative.

Nature of polyamorphic transformations in H2O under isothermal compression and decompression

We report polyamorphic transformations of ${\mathrm{H}}_{2}\mathrm{O}$ under isothermal compression and decompression at 150 K, observed by in situ x-ray diffraction. Detailed structural information across the transformations among low-, high-, and very-high-density amorphs (LDA, HDA, and VHDA) reveals the mechanisms, the reversibility, and (dis)continuity of the transformations. During isothermal (de)compression, the polyamorphic transformations are characterized by a sharp and reversible LDA-VHDA transformation, with an HDA-like form (referred to as HDA\ensuremath{'}) appearing as an intermediate state. The LDA-VHDA transformation is found to occur in two steps: a discontinuous transition between LDA and the end member of HDA\ensuremath{'} on the low-pressure side, followed by a continuous change within HDA\ensuremath{'} involving structural reconfigurations and finally converging to VHDA. Both LDA and VHDA are found to be structurally stable showing mainly elastic behavior under (de)compression, while HDA\ensuremath{'} is structurally unstable. Possible relations of these observations to low- and high-density liquids are discussed.

Using pressure to probe thermodynamic anomalies in tetrahedrally-bonded materials

Tetrahedrally-bonded materials, such as silicon, diamond, or gallium nitride, are characterized by a low coordination number of 4 in the crystalline phase and, in general, can exhibit a liquid phase with higher density and coordination. This leads to interesting thermodynamic behavior, including the lowering of the melting temperature with increasing pressure and the possible existence of distinct low- and high-density liquid phases. Using molecular dynamics simulations, we explored the role of pressure and the degree of tetrahedrality on the structure and phase equilibria between the crystalline and liquid phases of tetrahedrally-bonded materials. In addition to the thermodynamic melting point, we determined the temperature of mechanical stability (spinodal temperature) as a function of pressure. The latter temperature is relevant to the laser pulse rapid melting of tetrahedrally-bonded materials. The results of our simulations indicate the possibility of the existence of a thermodynamically stable low-density liquid phase of silicon at high pressures. Our simulation also suggests that GaN is unlikely to exhibit anomalous thermodynamic behavior due to a high degree of tetragonality preventing the formation of high-density liquid, even at high pressures.

Li-Na-metasomatism related to I-type granite magmatism: A case study of the highly fractionated La Pedriza pluton (Iberian Variscan belt)

This study describes rare albitites associated with highly fractionated I-type granitic melts, showing a mineral paragenesis that resembles those of high-temperature metasomatized rocks (fenites) associated with alkaline and carbonatitic intrusions. The studied albitites occur as lenticular bodies on the meter scale, hosted in peraluminous granites, and are scattered in a narrow sector next to the peraluminous and highly fractionated I-type La Pedriza leucogranite (LPL) pluton in the Spanish Central System. Albitites show sharp contacts and preserve textural features of the host granites (i.e., isovolumetric metasomatism). These rocks consist of a variably albitized magmatic feldspar framework (70–85 modal %) and interstitial domains where singular Na-Li-Fe3+-rich amphiboles and pyroxenes crystallized with albite or quartz. Titanite, andradite-grossular garnet, Mg-Li-rich mica, magnetite, fluorite, and apatite are metasomatic accessory minerals. Mass balance indicates enrichments of Na2O, FeO, MgO, MnO, Li, F, Be, and some HFSE (high-field-strength elements, such as Zn, Sc, and Sn) and LILE (large-ion lithophile elements) depletion. U-Pb data from metasomatic titanite yield 307 ± 10 Ma, which is coeval with the LPL and within the range of the regional granite emplacement (about 309–298 Ma). The LPL also shows strong compositional affinities (F, Li, Na, Sn, and Zn enrichment) with albitites. Similar Sr-Nd-δD isotopic signatures between albitites and host granites suggest that magmatic fluids might be dominant during metasomatism. However, the heterogeneity of δ18O, which shifts toward lower values in the more distant outcrops, suggests contribution of meteoric in origin low-salinity waters during prograde metasomatism. P-T-fO2 conditions are estimated at 0.2–0.3 GPa, 645–700 °C, and relatively oxidized conditions. We propose that Na-HFSE-flux-rich residual melts of the LPL expelled two immiscible hot liquids: an alkaline low-density liquid and a high-density hydrosilicate liquid (HSL). The low-density fluid dissolved magmatic quartz and provided albitization of the magmatic feldspar framework by a diffusive mechanism. Quartz dissolution created microchannels for infiltration of the relatively low viscosity HSL, forming tubular channels. This fluid was enriched in network modifiers (Li, Na, F, Be) and cations (Ca, Al) released after albitization, and it precipitated in these microchannels to form the new metasomatic paragenesis (quartz, albite, uncommon Li-rich mafic silicates, and accessory minerals).

Liquid-liquid separation of aqueous solutions: A molecular dynamics study.

In the liquid-liquid phase transition scenario, supercooled water separates into the high density liquid (HDL) and low density liquid (LDL) phases at temperatures lower than the second critical point. We investigate the effects of hydrophilic and hydrophobic solutes on the liquid-liquid phase transition using molecular dynamics simulations. It is found that a supercooled aqueous NaCl solution separates into solute-rich HDL and solute-poor LDL parts at low pressures. By contrast, a supercooled aqueous Ne solution separates into solute-rich LDL and solute-poor HDL parts at high pressures. Both the solutes increase the high temperature limit of the liquid-liquid separation. The degree of separation is quantified using the local density of solute particles to determine the liquid-liquid coexistence region in the pressure-temperature phase diagram. The effects of NaCl and Ne on the phase diagram of supercooled water are explained in terms of preferential solvation of ions in HDL and that of small hydrophobic particles in LDL, respectively.

Simulations of supercooled water under passive or active stimuli

We use molecular dynamics simulations to study the behavior of supercooled water subject to different stimuli from a diluted azobenzene hydrophobic probe. When the molecular motor does not fold, it acts as a passive probe, modifying the structure of water around it, while when the motor is active, it induces elementary diffusion processes inside the medium acting mainly on the dynamics. We study two particular densities, the density of ambient water and a lower density around the ambient pressure ice density, chosen to favor high density liquid and low density liquid (LDL) water, respectively. We find that the passive probe induces ever an acceleration or a slowing down of the diffusion process around it depending on the density of water, while the active probe induces acceleration only. We find a crossover between the diffusion coefficients for the two densities near the passive probe, around T = 215 K. This dynamical crossover is associated with a modification of the structure of water near the probe. Structure calculations show a crossover of the proportion of LDL water around the same temperature, suggesting that it induces the observed dynamical crossover. In opposition with these results, the active stimuli increase diffusion for both densities and decrease the proportion of LDL water at low temperatures. However, we also find for the active stimuli a crossover of the LDL proportion between the two densities of study, showing remarkable similarities between active and passive stimulus results.

Thermal and nonthermal melting of III-V compound semiconductors

We study theoretically the response of group III-V compound semiconductors (AlAs, AlP, GaAs, GaP, GaSb) to free-electron laser irradiation, identifying their damage thresholds. The employed hybrid code XTANT is capable of modeling both thermal and nonthermal effects under ultrafast electronic excitation. It allowed us to reveal common trends in the studied materials: all but the AlAs III-V compounds studied here exhibit a phase transition into a metallic disordered state of lower density than the solid phase via a thermal phase transition. This transition is instigated by electron-ion coupling at doses below the nonthermal melting. Irradiated AlAs showed two possible phases produced: low-density and high-density liquid. We demonstrate that the transferrable tight-binding method within the Born-Oppenheimer approximation significantly overestimates the damage threshold predicting only nonthermal melting in comparison to a non-Born-Oppenheimer scheme, which accounts for both effects and their interplay.