Person: Sanz García, Eduardo Santiago
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First Name
Eduardo Santiago
Last Name
Sanz García
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Química Física
Area
Química Física
Identifiers
12 results
Search Results
Now showing 1 - 10 of 12
Item A potential model for the study of ices and amorphous water: TIP4P/Ice(Journal of Chemical Physics, 2005) Fernández Abascal, José Luis; Sanz García, Eduardo Santiago; García Fernández, Raúl; Vega De Las Heras, CarlosThe ability of several water models to predict the properties of ices is discussed. The emphasis is put on the results for the densities and the coexistence curves between the different ice forms. It is concluded that none of the most commonly used rigid models is satisfactory. A new model specifically designed to cope with solid-phase properties is proposed. The parameters have been obtained by fitting the equation of state and selected points of the melting lines and of the coexistence lines involving different ice forms. The phase diagram is then calculated for the new potential. The predicted melting temperature of hexagonal ice (Ih) at 1bar is 272.2K. This excellent value does not imply a deterioration of the rest of the properties. In fact, the predictions for both the densities and the coexistence curves are better than for TIP4P, which previously yielded the best estimations of the ice properties.Item Anomalous Behavior in the Nucleation of Ice at Negative Pressures(Physical Review Letters, 2021) Bianco, Valentino; Montero De Hijes, Pablo; Cintia P. Lamas; Sanz García, Eduardo Santiago; Carlos Vega; Vega De Las Heras, CarlosIce nucleation is a phenomenon that, despite the relevant implications for life, atmospheric sciences, and technological applications, is far from being completely understood, especially under extreme thermodynamic conditions. In this work we present a computational investigation of the homogeneous ice nucleation at negative pressures. By means of the seeding technique we estimate the size of the ice critical nucleus Nc for the TIP4P/Ice water model. This is done along the isotherms 230, 240, and 250 K, from positive to negative pressures until reaching the liquid-gas kinetic stability limit (where cavitation cannot be avoided). We find that Nc is nonmonotonic upon depressurization, reaching a minimum at negative pressures in the doubly metastable region of water. According to classical nucleation theory we establish the nucleation rate J and the surface tension γ, revealing a retracing behavior of both when the liquid-gas kinetic stability limit is approached. We also predict a reentrant behavior of the homogeneous nucleation line. The reentrance of these properties is related to the reentrance of the coexistence line at negative pressure, revealing new anomalies of water. The results of this work suggest the possibility of having metastable samples of liquid water for long times at negative pressure provided that heterogeneous nucleation is suppressed.Item Mechanosensitive Gold Colloidal Membranes Mediated by Supramolecular Interfacial Self-Assembly(Journal of the American Chemical Society, 2017) Coelho, João Paulo; Mayoral Muñoz, María José; Camacho, Luis; Martín-Romero, María T.; Tardajos Rodríguez, Gloria; López-Montero, Iván; Sanz García, Eduardo Santiago; Ávila Brande, David; Giner-Casares, Juan José; Fernández, Gustavo; Guerrero Martínez, AndrésThe ability to respond toward mechanical stimuli is a fundamental property of biological organisms at both the macroscopic and cellular levels, yet it has been considerably less observed in artificial supramolecular and colloidal homologues. An archetypal example in this regard is cellular mechanosensation, a process by which mechanical forces applied on the cell membrane are converted into biochemical or electrical signals through nanometer-scale changes in molecular conformations. In this article, we report an artificial gold nanoparticle (Au NP)−discrete π-conjugated molecule hybrid system that mimics the mechanical behavior of biological membranes and is able to self-assemble into colloidal gold nanoclusters or membranes in a controlled and reversible fashion by changing the concentration or the mechanical force (pressure) applied. This has been achieved by rational design of a small π-conjugated thiolated molecule that controls, to a great extent, the hierarchy levels involved in Au NP clustering by enabling reversible, cooperative non-covalent (π−π, solvophobic, and hydrogen bonding) interactions. In addition, the Au NP membranes have the ability to entrap and release aromatic guest molecules reversibly (Kb = 5.0 × 105 M−1 ) for several cycles when subjected to compression−expansion experiments, in close analogy to the behavior of cellular mechanosensitive channels. Not only does our hybrid system represent the first example of a reversible colloidal membrane, but it also can be controlled by a dynamic mechanical stimulus using a new supramolecular surface-pressure-controlled strategy. This approach holds great potential for the development of multiple colloidal assemblies within different research fields.Item A simulation study of homogeneous ice nucleation in supercooled salty water(Journal of chemical physics, 2018) Soria, Guiomar D.; Espinosa, Jorge R.; Ramirez, Jorge; Valeriani, Chantal; Vega De Las Heras, Carlos; Sanz García, Eduardo SantiagoWe use computer simulations to investigate the effect of salt on homogeneous ice nucleation. The melting point of the employed solution model was obtained both by direct coexistence simulations and by thermodynamic integration from previous calculations of the water chemical potential. Using a seeding approach, in which we simulate ice seeds embedded in a supercooled aqueous solution, we compute the nucleation rate as a function of temperature for a 1.85 NaCl mol per water kilogram solution at 1 bar. To improve the accuracy and reliability of our calculations, we combine seeding with the direct computation of the ice-solution interfacial free energy at coexistence using the Mold Integration method. We compare the results with previous simulation work on pure water to understand the effect caused by the solute. The model captures the experimental trend that the nucleation rate at a given supercooling decreases when adding salt. Despite the fact that the thermodynamic driving force for ice nucleation is higher for salty water for a given supercooling, the nucleation rate slows down with salt due to a significant increase of the ice-fluid interfacial free energy. The salty water model predicts an ice nucleation rate that is in good agreement with experimental measurements, bringing confidence in the predictive ability of the model. We expect that the combination of state-of-the-art simulation methods here employed to study ice nucleation from solution will be of much use in forthcoming numerical investigations of crystallization in mixtures. Published by AIP Publishing.Item Disjoining Pressure, Healing Distance and Film Height Dependent Surface Tension of Thin Wetting Films(Journal of Physical Chemistry C, 2014) Benet, Jorge; G. Palanco, José; Sanz García, Eduardo Santiago; G. MacDowell, LuisIn this work we simulate the adsorption of wetting liquid argon films on a model substrate. We calculate the disjoining pressure isotherm and show that it is completely dominated by the long range van der Waals interactions. Thick films exhibit the expected Hamaker power law decay, but a quantitative description of thin films requires consideration of the detailed structure of the adsorbed layer. The spectrum of film height fluctuations is calculated, and shown to provide reliable estimates of the disjoining pressure for all films studied. However, it is observed that the full spectrum can only be reproduced provided that we account for a film height dependent surface tension proportional to the derivative of the disjoining pressure. A simple theory is worked out that describes well the observed film height dependence. Having at hand both the surface tension and the disjoining pressure, we calculate the healing distance of the liquid films, which differs from the classical expectation by a constant of the same order of magnitude as the bulk correlation length. We show these findings have important implications on the behavior of adsorbed liquids and determine corrections to the augmented Young-Laplace equation at the subnanometer length scale.Item Solubility of Methane in Water: Some Useful Results for Hydrate Nucleation(The Journal of Physical Chemistry B, 2022) Grabowska, Joanna; Blázquez Fernández, Samuel; Sanz García, Eduardo Santiago; Zerón, Iván M.; Algaba, Jesús; Míguez, José Manuel; Blas, Felipe J.; Vega De Las Heras, CarlosIn this paper, the solubility of methane in water along the 400 bar isobar is determined by computer simulations using the TIP4P/Ice force field for water and a simple LJ model for methane. In particular, the solubility of methane in water when in contact with the gas phase and the solubility of methane in water when in contact with the hydrate has been determined. The solubility of methane in a gas–liquid system decreases as temperature increases. The solubility of methane in a hydrate–liquid system increases with temperature. The two curves intersect at a certain temperature that determines the triple point T3 at a certain pressure. We also determined T3 by the three-phase direct coexistence method. The results of both methods agree, and we suggest 295(2) K as the value of T3 for this system. We also analyzed the impact of curvature on the solubility of methane in water. We found that the presence of curvature increases the solubility in both the gas–liquid and hydrate–liquid systems. The change in chemical potential for the formation of hydrate is evaluated along the isobar using two different thermodynamic routes, obtaining good agreement between them. It is shown that the driving force for hydrate nucleation under experimental conditions is higher than that for the formation of pure ice when compared at the same supercooling. We also show that supersaturation (i.e., concentrations above those of the planar interface) increases the driving force for nucleation dramatically. The effect of bubbles can be equivalent to that of an additional supercooling of about 20 K. Having highly supersaturated homogeneous solutions makes possible the spontaneous formation of the hydrate at temperatures as high as 285 K (i.e., 10K below T3). The crucial role of the concentration of methane for hydrate formation is clearly revealed. Nucleation of the hydrate can be either impossible or easy and fast depending on the concentration of methane which seems to play the leading role in the understanding of the kinetics of hydrate formation.Item Seeding approach to nucleation in the NVT ensemble: The case of bubble cavitation in overstretched Lennard Jones fluids(Physical review E, 2020) Rosales Peláez, Pablo; Sánchez Burgos, Ignacio; Valeriani, Chantal; Vega De Las Heras, Carlos; Sanz García, Eduardo SantiagoSimulations are widely used to study nucleation in first order phase transitions due to the fact that they have access to the relevant length and time scales. However, simulations face the problem that nucleation is an activated process. Therefore, rare event simulation techniques are needed to promote the formation of the critical nucleus. The Seeding method, where the simulations are started with the nucleus already formed, has proven quite useful in efficiently providing estimates of the nucleation rate for a wide range of orders of magnitude. So far, Seeding has been employed in the NPT ensemble, where the nucleus either grows or redissolves. Thus, several trajectories have to be run in order to find the thermodynamic conditions that make the seeded nucleus critical. Moreover, the nucleus lifetime is short and the statistics for obtaining its properties is consequently poor. To deal with these shortcomings we extend the Seeding method to the NVT ensemble. We focus on the problem of bubble nucleation in a metastable Lennard Jones fluid. We show that, in the NVT ensemble, it is possible to equilibrate and stabilise critical bubbles for a long time. The nucleation rate inferred from NVT-Seeding is fully consistent with that coming from NPT-Seeding. The former is quite suitable to obtain the nucleation rate along isotherms, whereas the latter is preferable if the dependence of the rate with temperature at constant pressure is required. Care should be taken with finite size effects when using NVT-Seeding. Further work is required to extend NVT seeding to other sorts of phase transitions.Item Structure and fluctuations of the premelted liquid film of ice at the triple point(Molecular Physics, 2019) Benet, Jorge; Llombart, Pablo; Sanz García, Eduardo Santiago; MacDowell, Luis G.In this paper we study the structure of the ice/vapor interface in the neighborhood of the triple point for the TIP4P/2005 model. We probe the fluctuations of the ice/film and film/vapor surfaces that separate the liquid film from the coexisting bulk phases at basal, primary prismatic and secondary prismatic planes. The results are interpreted using a coupled sine Gordon plus Interface Hamiltonian model. At large length-scales, the two bounding surfaces are correlated and behave as a single complex ice/vapor interface. For small length, on the contrary, the ice/film and film/vapor surfaces behave very much like independent ice/water and water/vapor interfaces. The study suggests that the basal facet of the TIP4P/2005 model is smooth, the prismatic facet is close to a roughening transition, and the secondary prismatic facet is rough. For the faceted basal face, our fluctuation analysis allows us to estimate the step free energy in good agreement with experiment. Our results allow for a quantitative characterization of the extent to which the adsorbed quasi-liquid layer behaves as water, and explains experimental observations which reveal similar activation energies for crystals grown in bulk vapor or bulk water.Item Premelting-Induced Smoothening of the Ice-Vapor Interface(Physical Review Letters, 2016) Benet, Jorge; Llombart, Pablo; Sanz García, Eduardo Santiago; González Mac-Dowell, LuisWe perform computer simulations of the quasiliquid layer of ice formed at the ice-vapor interface close to the ice Ih-liquid-vapor triple point of water. Our study shows that the two distinct surfaces bounding the film behave at small wavelengths as atomically rough and independent ice-water and water-vapor interfaces. For long wavelengths, however, the two surfaces couple, large scale parallel fluctuations are inhibited, and the ice-vapor interface becomes smooth. Our results could help explain the complex morphology of ice crystallites.Item Seeding approach to bubble nucleation in superheated Lennard-Jones fluids(Physical review E, 2019) Rosales Peláez, Pablo; García Cid, M. I.; Valeriani, Chantal; Vega De Las Heras, Carlos; Sanz García, Eduardo SantiagoWe investigate vapor homogeneous nucleation in a superheated Lennard-Jones liquid with computer simulations. Special simulation techniques are required to address this study since the nucleation of a critical vapor bubble-one that has an equal chance to grow or shrink-in a moderately superheated liquid is a rare event. We use the Seeding method, which combines Classical Nucleation Theory with computer simulations of a liquid containing a vapor bubble to provide bubble nucleation rates in a wide temperature range. Seeding has been successfully applied to investigate the nucleation of crystals in supercooled fluids, and here we apply it to the liquid-to-vapor transition. We find that the Seeding method provides nucleation rates that are consistent with independent calculations not based on the assumptions of Classical Nucleation Theory. Different criteria to determine the radius of the critical bubble give different rate values. The accuracy of each criterion depends of the degree of superheating. Moreover, seeding simulations show that the surface tension depends on pressure for a given temperature. Therefore, using Classical Nucleation Theory with the coexistence surface tension does not provide good estimates of the nucleation rate.