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  • The force matching approach to multiscale simulations: merits, shortcomings, and future perspectives

     Masia, Marco; Guardia Manuel, Elvira; Nicolini, Paolo
    International journal of quantum chemistry
    Vol. 114, num. 16, p. 1036-1040
    DOI: 10.1002/qua.24621
    Date of publication: 2014-08-15
    Journal article

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    Among the various approaches to multiscale simulations, in recent years, force matching has been known for a quick growth. The method is based on a least-square fit of reference properties obtained from simulations at a certain scale, to parameterize the force field for coarser-grained scale simulations. Its advantage with respect to conventional schemes used for parameterizing force fields, lies in that only physically accessible configurations are sampled, and that the number of reference data per configuration is large. In this perspective article, we discuss some recent findings on the tailoring of the objective function, on the choice of the empirical potential, and on the way to improve the quality of the reference calculations. We present pros and cons of the algorithm, and we propose a road map to future developments. (C) 2014 Wiley Periodicals, Inc.

    Among the various approaches to multiscale simulations, in recent years, force matching has been known for a quick growth. The method is based on a least-square fit of reference properties obtained from simulations at a certain scale, to parameterize the force field for coarser-grained scale simulations. Its advantage with respect to conventional schemes used for parameterizing force fields, lies in that only physically accessible configurations are sampled, and that the number of reference data per configuration is large. In this perspective article, we discuss some recent findings on the tailoring of the objective function, on the choice of the empirical potential, and on the way to improve the quality of the reference calculations. We present pros and cons of the algorithm, and we propose a road map to future developments. (C) 2014 Wiley Periodicals, Inc.

  • Characterization of the methane-graphene hydrophobic interaction in aqueous solution from ab initio simulations

     Calero Borrallo, Carles; Masia, Marco; Marti Rabassa, Jordi; Guardia Manuel, Elvira
    WaterEurope 2014
    p. 56
    Presentation's date: 2014-06-13
    Presentation of work at congresses

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    The interaction between a methane molecule and a graphene plane in liquid water has been characterized employing DFT-based free energy Molecular Dynamics calculations. This system represents a good model to understand the generic interaction between a small hydrophobic solute (methane molecule) and an extense hydrophobic surface (graphene plane). The structural and dynamical properties of graphene and methane hydration water are analyzed and found to be closely related to the main features of the potential of mean force. The results could be used in coarse-grained models to take into account the effect of the hydrophobic interaction in realistic systems relevant to experiment.

  • The structure of water beyond the first coordination shell

     Pardo Soto, Luis Carlos; Henao Aristizábal, Andres; Guardia Manuel, Elvira; Tamarit Mur, Jose Luis
    WaterEurope
    p. 65
    Presentation's date: 2014-06-12
    Presentation of work at congresses

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  • Insights into the determination of molecular structure from diffraction data using a Bayesian algorithm

     Henao Aristizábal, Andres; Rovira Esteva, Muriel; Vispa, Alessandro; Tamarit Mur, Jose Luis; Guardia Manuel, Elvira; Pardo Soto, Luis Carlos
    Journal of physics: condensed matter
    Vol. 25, num. 45
    DOI: 10.1088/0953-8984/25/45/454217
    Date of publication: 2013-11-13
    Journal article

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    The determination of the molecular ordering in a liquid is still a controversial subject. There is no general consensus either on the methods to obtain reliable liquid structures or on the way to analyze them. Regardless of the method, it is very important to have a realistic molecular structure available that allows simulations to faithfully reproduce the sample features, and that minimizes the computing time in structure refinements. However, attention is not always paid to this point and molecular models coming from general force-fields are frequently used to undertake many of the analyses. We propose in this work to use a Bayesian scheme to fit the experimental data and produce reliable molecular models that can be used as the starting point of any simulation or refinement. The algorithm behind the proposed method is based on a Markov chain Monte Carlo procedure, as many other refinement programs such as reverse Monte Carlo or empirical potential structure refinement.

  • Characterization of the methane¿graphene hydrophobic interaction in aqueous solution from ab initio simulations

     Calero Borrallo, Carles; Marti Rabassa, Jordi; Guardia Manuel, Elvira; Masia, Marco
    Journal of chemical theory and computation
    Vol. 9, num. 11, p. 5070-5075
    DOI: 10.1021/ct400554q
    Date of publication: 2013-09-17
    Journal article

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    In this article, the interaction between a methane molecule and a graphene plane in liquid water has been characterized employing DFT-based free energy Molecular Dynamics calculations. This system represents a good model to understand the generic interaction between a small hydrophobic solute (methane molecule) and an extense hydrophobic surface (graphene plane). The structural and dynamical properties of graphene and methane hydration water are analyzed and found to be closely related to the main features of the potential of mean force. The results could be used in coarse-grained models to take into account the effect of the hydrophobic interaction in realistic systems relevant to experiment.

    In this article, the interaction between a methane molecule and a graphene plane in liquid water has been characterized employing DFT-based free energy Molecular Dynamics calculations. This system represents a good model to understand the generic interaction between a small hydrophobic solute (methane molecule) and an extense hydrophobic surface (graphene plane). The structural and dynamical properties of graphene and methane hydration water are analyzed and found to be closely related to the main features of the potential of mean force. The results could be used in coarse-grained models to take into account the effect of the hydrophobic interaction in realistic systems relevant to experiment.

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    Shortcomings of the standard Lennard-Jones dispersion term in water models, studied with force matching  Open access

     Nicolini, Paolo; Guardia Manuel, Elvira; Masia, Marco
    Journal of chemical physics
    Vol. 139, num. 18, p. 184111-1-184111-5
    DOI: 10.1063/1.4829444
    Date of publication: 2013-11-14
    Journal article

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    In this work, ab initio parametrization of water force field is used to get insights into the functional form of empirical potentials to properly model the physics underlying dispersion interactions. We exploited the force matching algorithm to fit the interaction forces obtained with dispersion corrected density functional theory based molecular dynamics simulations. We found that the standard Lennard-Jones interaction potentials poorly reproduce the attractive character of dispersion forces. This drawback can be resolved by accounting for the distinctive short range behavior of dispersion interactions, multiplying the r-6 term by a damping function. We propose two novel parametrizations of the force field using different damping functions. Structural and dynamical properties of the new models are computed and compared with the ones obtained from the non-damped force field, showing an improved agreement with reference first principle calculations.

    In this work, ab initio parametrization of water force field is used to get insights into the functional form of empirical potentials to properly model the physics underlying dispersion interactions. We exploited the force matching algorithm to fit the interaction forces obtained with dispersion corrected density functional theory based molecular dynamics simulations. We found that the standard Lennard-Jones interaction potentials poorly reproduce the attractive character of dispersion forces. This drawback can be resolved by accounting for the distinctive short range behavior of dispersion interactions, multiplying the r −6 term by a damping function. We propose two novel parametrizations of the force field using different damping functions. Structural and dynamical properties of the new models are computed and compared with the ones obtained from the non-damped force field, showing an improved agreement with reference first principle calculations.

  • Determination of the short range order of molecular liquids: a general method

     Pardo Soto, Luis Carlos; Rovira Esteva, Muriel; Henao Aristizábal, Andres; Silva-Santisteban López, Alvaro; Murugan Natarajan, Arul; Cuello, Gabriel Julio; Gonzalez Lopez, Miguel Angel; Guardia Manuel, Elvira; Tamarit Mur, Jose Luis
    International Discussion Meeting on Relaxation in Complex Systems
    p. 197
    Presentation's date: 2013-07-26
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  • Methane-graphene potential of mean force from DFT-based molecular dynamics simulations

     Calero Borallo, Carlos; Masia, Marco; Marti Rabassa, Jordi; Guardia Manuel, Elvira
    WaterSpain
    p. 33
    Presentation's date: 2013-02-08
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  • Confinement effects on the structure and dynamics of water and aqueous ionic solutions

     Sala Viñas, Jonàs
    Department of Physics and Nuclear Engineering, Universitat Politècnica de Catalunya
    Theses

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    Excess protons in mesoscopic water-acetone nanoclusters  Open access

     Semino, Rocío; Marti Rabassa, Jordi; Guardia Manuel, Elvira; Laria, Daniel
    Journal of chemical physics
    Vol. 137, num. 19, p. 1-8
    DOI: 10.1063/1.4766201
    Date of publication: 2012-11-19
    Journal article

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    We carried out molecular dynamics simulation experiments to examine equilibrium and dynamical characteristics of the solvation of excess protons in mesoscopic, [m:n] binary polar clusters comprising m = 50 water molecules and n = 6, 25, and 100 acetone molecules. Contrasting from what is found in conventional macroscopic phases, the characteristics of the proton solvation are dictated, to a large extent, by the nature of the concentration fluctuations prevailing within the clusters. At low acetone contents, the overall cluster morphology corresponds to a segregated aqueous nucleus coated by an external aprotic phase. Under these circumstances, the proton remains localized at the surface of the water core, in a region locally deprived from acetone molecules. At higher acetone concentrations, we found clear evidence of the onset of the mixing process. The cluster structures present aqueous domains with irregular shape, fully embedded within the acetone phase. Still, the proton remains coordinated to the aqueous phase, with its closest solvation shell composed exclusively by three water molecules. As the relative concentration of acetone increases, the time scales characterizing proton transfer events between neighboring water molecules show considerable retardations, stretching into the nanosecond time domain already for n ∼ 25. In water-rich aggregates, and similarly to what is found in the bulk, proton transfers are controlled by acetone/water exchange processes taking place at the second solvation shell of the proton. As a distinctive feature of the transfer mechanism, translocation pathways also include diffusive motions of the proton from the surface down into inner regions of the underlying water domain.

  • Aqueous halide potentials from force matching of Car-Parrinello data

     Spångberg, Daniel; Guardia Manuel, Elvira; Masia, Marco
    Computational and theoretical chemistry
    Vol. 982, p. 58-65
    DOI: 10.1016/j.comptc.2011.12.011
    Date of publication: 2012-02-15
    Journal article

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    Recently many various research groups have devoted a huge effort to develop a realistic classical force field for ions in water. The parametrization techniques used could be gathered into two classes: (i) fit of the ab initio potential energy surface for clusters at gas phase, and (ii) fit of experimental properties. For both classes of force fields, a high level of accuracy has been achieved, which has led to important improvements in the modeling of ion–water systems. In this paper a new, complementary, approach is proposed to overcome the limitations and to get a deeper insight into the atomistic description of ion–water interactions. We use the recently developed force matching method to parametrize classical halide–water force fields for three different water models. Here we discuss both methodological issues and the level of agreement between the results obtained using this method to Car–Parrinello simulation results.

  • Fitting properties from density functional theory based molecular dynamics simulations to parameterize a rigid water force field

     Sala Viñas, Jonàs; Guardia Manuel, Elvira; Marti Rabassa, Jordi; Spångberg, Daniel; Masia, Marco
    Journal of chemical physics
    Vol. 136, num. 5, p. 054103-1-054103-10
    DOI: 10.1063/1.3679402
    Date of publication: 2012-02-02
    Journal article

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    In the quest towards coarse-grained potentials and new water models, we present an extension of the force matching technique to parameterize an all-atom force field for rigid water. The methodology presented here allows to improve the matching procedure by first optimizing the weighting exponents present in the objective function. A new gauge for unambiguously evaluating the quality of the fit has been introduced; it is based on the root mean square difference of the distributions of target properties between reference data and fitted potentials. Four rigid water models have been parameterized; the matching procedure has been used to assess the role of the ghost atom in TIP4P-like models and of electrostatic damping. In the former case, burying the negative charge inside the molecule allows to fit better the torques. In the latter, since short-range interactions are damped, a better fit of the forces is obtained. Overall, the best performing model is the one with a ghost atom and with electrostatic damping. The approach shown in this paper is of general validity and could be applied to any matching algorithm and to any level of coarse graining, also for non-rigid molecules.

  • Specific ion effects in aqueous eletrolyte solutions confined within graphene sheets at the nanometric scale

     Sala Viñas, Jonàs; Guardia Manuel, Elvira; Marti Rabassa, Jordi
    Physical chemistry chemical physics
    Vol. 14, num. 30, p. 10799-10808
    DOI: 10.1039/C2CP40537G
    Date of publication: 2012-08-14
    Journal article

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    The underlying mechanisms of specific ion effects on structure and dynamics of aqueous solutions have been long debated. On the other hand, the role of polarization at hydrophobic interfaces when aqueous electrolytes are present is of great importance, as it has been observed at the air–vapor interface. In this work, we have explored influence of ionic species on microscopical properties of aqueous sodium halide solutions constrained inside a double layer graphene channel, as a model for a realistic hydrophobic interface. Our systems have been simulated by molecular dynamics techniques, explicitly including polarization in water molecules and ions. Water and ionic density profiles showed the tendency of ionic species to occupy the whole space available, in good agreement with spectroscopic experimental data. The exception to this general behavior was fluoride, which preferred to stay away from interfaces. Two main regions were defined: interfaces and the central part of the slab, the bulklike region. Ionic hydration numbers at interfaces were lower than those at the bulklike area by about one to two units. We have also analyzed water–ion orientations and polarization distributions and obtained a marked dependence on ionic concentration. Residence time of anions suffered important fluctuations and tended to be largest at interfaces. Large variations of the static permittivity between interfacial and bulklike regions were observed. Ionic diffusion was found to be between 10 5 and 10 6 cm2 s 1 and showed to be mainly dependent on the concentration, whereas the type of anion considered and the polarizability had significantly less relevance. Conductivities were found to be dependent on ionic concentrations and the polarizabilities of anions, as well as on the spatial direction considered.

  • Theoretical study of the H-NMR relaxation times in aqueous ionic solutions

     Calero Borallo, Carlos; Guardia Manuel, Elvira; Marti Rabassa, Jordi
    Física Estadística 2012 XVIII Congreso de Física Estadística
    p. 74
    Presentation's date: 2012-10-19
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  • Short range order of CCI:a comparison of RMC and MD Methods

     Pardo Soto, Luis Carlos; Silva-Santisteban López, Alvaro; Pothoczki, Szilvia; Bermejo, F. Javier; Henao Aristizábal, Andres; Tamarit Mur, Jose Luis; Guardia Manuel, Elvira; Cuello, G. J.
    Reunión de la Sociedad Española de Técnicas Neutrónicas
    p. 58
    Presentation's date: 2012-06-25
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    Aqueous electrolytes confined within functionalized silica nanopores  Open access

     Videla, Pablo; Marti Rabassa, Jordi; Guardia Manuel, Elvira; Laria, Daniel; Sala2 Viñas, Jonàs
    Journal of chemical physics
    Vol. 135, num. 10, p. 104503-1-104503-6
    DOI: 10.1063/1.3632050
    Date of publication: 2011-09-09
    Journal article

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    Molecular dynamics simulations have been carried out to investigate structural and dynamical characteristics of NaCl aqueous solutions confined within silica nanopores in contact with a “bulk-like” reservoir. Two types of pores, with diameters intermediate between 20 Å and 37.5 Å, were investigated: The first one corresponded to hydrophobic cavities, in which the prevailing wall-solution interactions were of the Lennard-Jones type. In addition, we also examined the behavior of solutions trapped within hydrophilic cavities, in which a set of unsaturated O-sites at the wall were transformed in polar silanol Si–OH groups. In all cases, the overall concentrations of the trapped electrolytes exhibited important reductions that, in the case of the narrowest pores, attained 50% of the bulk value. Local concentrations within the pores also showed important fluctuations. In hydrophobic cavities, the close vicinity of the pore wall was coated exclusively by the solvent, whereas in hydrophilic pores, selective adsorption of Na+ ions was also observed. Mass and charge transport were also investigated. Individual diffusion coefficients did not present large codifications from what is perceived in the bulk; contrasting, the electrical conductivity exhibited important reductions. The qualitative differences are rationalized in terms of simple geometrical considerations.

  • Improving the force matching algorithm: Application to a simple point charge flexible model of water

     Guardia Manuel, Elvira; Masia, Marco; Sala2 Viñas, Jonàs
    Computer physics communications
    Vol. 182, num. 9, p. 1954-1957
    DOI: 10.1016/j.cpc.2010.12.004
    Date of publication: 2011-09
    Journal article

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    In the last years the force matching algorithm has appeared to be a promising method for deriving next generation classical force fields. Recently it has been successfully utilized to parameterize new water models based on pairwise potentials. In this contribution we will present a refined version of the method which has been applied to parameterize a new force field for flexible water. Static and dynamical properties of the new water model reproduce fairly well the ab initio results. This enriched version of the method could possibly be applied to produce a fully flexible force field for any molecular systems where intramolecular motion plays a central role.

  • Aqueous electrolyte solutions within functionalized silica nanopores

     Marti Rabassa, Jordi; Videla, Pablo; H. Laria, Daniel; Guardia Manuel, Elvira; Sala2 Viñas, Jonàs
    Liquid Matter Conference
    p. Session 7-71
    Presentation's date: 2011-09-08
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  • Confined aqueous electrolytes within cylindrical nanocavities

     Videla, Pablo; H. Laria, Daniel; Marti Rabassa, Jordi; Guardia Manuel, Elvira; Sala2 Viñas, Jonàs
    Congreso de Física Estadística
    p. 201
    Presentation's date: 2011-06-03
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  • PROPIEDADES DINAMICAS EN FASES LIQUIDAS: SALES FUNDIDAS, DISOLUCIONES IONICAS Y LIQUIDOS MOLECULARES

     Sese Castel, Gemma; Rey Oriol, Rosendo; Trullàs Simó, Joaquim; Ortiz de Urbina Viade, Jordi; Canales Gabriel, Manel; Marti Rabassa, Jordi; Bitrian Varea, Vicente; Calvo Minguillon, Ausias March; Sala2 Viñas, Jonàs; Guardia Manuel, Elvira
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  • Effects of concentration on structure, dielectric, and dynamic properties of aqueous NaCl solutions using a polarizable model

     Sala2 Viñas, Jonàs; Guardia Manuel, Elvira; Marti Rabassa, Jordi
    Journal of chemical physics
    Vol. 132, num. 21, p. 214505-1-214505-11
    DOI: 10.1063/1.3429253
    Date of publication: 2010-06-03
    Journal article

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    The study of NaCl solutions in water at finite concentration, explicitly including polarization in water molecules and ions, has been carried out by molecular dynamics simulations. A comparison of the RPOL polarizable model with the rigid SPC/E potential for water has been included. Structure obtained with the two models does not show significant differences, although some deviations in the NaNa radial distribution functions at all concentrations are observed. Dielectric properties such as total and molecular dipole moment correlation functions revealed decay times of the order of 10 ps, roughly independent of concentration. The analysis of electric conductivity by means of current-current correlation functions also included the calculation of cross terms corresponding to dipole moment-current correlations, which proved to be non-neglectable at short times and especially relevant at high concentrations (m = 4 mol kg−1). Frequency dependent dielectric constants and conductivities have been computed and the role of cross correlations has been analyzed. In all cases both concentration and cross correlations have significant influence in the results

  • The polarizable point dipoles method with electrostatic damping: Implementation on a model system

     Guardia Manuel, Elvira; Masia, Marco; Sala2 Viñas, Jonàs
    Journal of chemical physics
    Vol. 133, num. 23, p. 1-14
    DOI: 10.1063/1.3511713
    Date of publication: 2010-12-21
    Journal article

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  • Molecular dynamics simulations of water confined in graphene nanochannels: From ambient to supercritical environments

     Marti Rabassa, Jordi; Guardia Manuel, Elvira; Sala2 Viñas, Jonàs
    Journal of molecular liquids
    Vol. 153, num. 1, p. 72-78
    DOI: 10.1016/j.molliq.2009.09.015
    Date of publication: 2010-03-31
    Journal article

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    Effect of the local hydrogen bonding network on the reorientational and translational dynamics in supercritical water  Open access

     Skarmoutsos, Ioannis; Guardia Manuel, Elvira
    Journal of chemical physics
    Vol. 132, num. 7, p. 1-10
    DOI: 10.1063/1.3305326
    Date of publication: 2010-02
    Journal article

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    Molecular dynamics simulations have been performed in a wide range of densities along a near critical isotherm of supercritical water in order to reveal the interconnection between the local hydrogen bonding (HB) network and several related dynamic properties. The results obtained have revealed a significant slowing down of reorientational dynamics of the water molecules as the value of the number of hydrogen bond per molecule increases and this is reflected on the increase in the reorientational correlation times. The calculated reorientational times exhibit also an increasing trend by increasing the bulk density, and this effect is more pronounced in the case of the first-order Legendre reorientational correlation functions. A clear nonlinear dependence of the librational mode frequencies of the water molecules on the augmented local density around them has also been revealed. This result could be regarded as an additional support of experimental observations suggesting the use of a nonlinear relation when analyzing the density dependence of spectroscopic peak frequencies in order to extract information about local density augmentation in supercritical fluids. The HB dynamics have been also investigated, revealing a plateau in the calculated HB lifetimes at intermediate and higher liquidlike densities and a small increase at low, gaslike densities.

  • GRUP DE SIMULACIO PER ORDINADOR EN MATERIA CONDENSADA

     Pastor Satorras, Romualdo; Sese Castel, Gemma; Rey Oriol, Rosendo; Casulleras Ambros, Joaquin; Trullàs Simó, Joaquim; Bitrian Varea, Vicente; Baronchelli, Andrea; Osychenco, Oleg; Canales Gabriel, Manel; Boronat Medico, Jordi; Marti Rabassa, Jordi; Macia Rey, Adrian; Calvo Minguillon, Ausias March; Ortiz de Urbina Viade, Jordi; Mazzanti Castrillejo, Fernando Pablo; Astrakharchik, Grigori; Rota, Riccardo; Sala2 Viñas, Jonàs; Guardia Manuel, Elvira
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  • Structure and dynamics of liquid water inside reverse micelles

     Marti Rabassa, Jordi; Guardia Manuel, Elvira; Rodriguez, Javier; Daniel, Laria
    Faraday Discussion 144: Multiscale Modelling of Soft Matter
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  • Local structural effects and related dynamics in supercritical ethanol. 1. Mechanisms of local density reorganization and residence dynamics

     Skarmoutsos, Ioannis; Guardia Manuel, Elvira
    Journal of physical chemistry B
    Vol. 113, p. 8887-8897
    DOI: 10.1021/jp901020x
    Date of publication: 2009
    Journal article

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    The length scale effects on the relaxation processes describing the local density reorganization and residence dynamics of pure supercritical ethanol have been systematically investigated by employing molecular dynamics simulation techniques. The calculated static local density augmentation and enhancement values of ethanol have been found to be comparable to those of methanol at similar conditions but significantly lower than those of the strong associating fluid water, indicating thus the effect of hydrogen-bonding interactions on the creation of local density inhomogeneities in supercritical fluids. The bulk density dependence of local density reorganization dynamics has been studied as a function of the shell cutoff radius, revealing a significant change at length scales higher than the position of the first maximum of the radial pair distribution function. At length scales higher than this cutoff, the local density inhomogeneities affect more significantly the reorganization of the local environment and this becomes even more apparent at length scales corresponding to the second solvation shell radius. Additionally, the residence dynamics for the region extending up to the first solvation shell of ethanol was investigated, and the results obtained reveal that the density dependence of local density dynamics exhibit differences in correspondence to local density dynamics, something which becomes also apparent at length scales higher than the position of the first peak of the radial pair distribution function.

  • On Ion and Molecular Polarization of Halides in Water

     Guardia Manuel, Elvira; Skarmoutsos, I; Masia, M
    Journal of chemical theory and computation
    Vol. 5, num. 6, p. 1449-1453
    Date of publication: 2009-06
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  • Local structural effects and related dynamics in supercritical ethanol. 2. Hydrogen-bonding network and its effect on single reorientational dynamics

     Skarmoutsos, Ioannis; Guardia Manuel, Elvira
    Journal of physical chemistry B
    Vol. 113, p. 8898-8910
    DOI: 10.1021/jp901489c
    Date of publication: 2009
    Journal article

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    The local hydrogen-bonding (HB) network and its possible interconnection with the single reorientational dynamics in pure supercritical (sc) ethanol have been systematically investigated by employing molecular dynamics simulation techniques. The results obtained reveal a nonlinear density dependence of the calculated average number of hydrogen bonds 〈nHB〉, similar to that of the calculated coordination numbers Nc, signifying also the interrelation between the local HB network and the local density augmentation in sc ethanol. Additionally, the HB dynamics were investigated in terms of several appropriate time correlation functions. The results obtained reveal that the density dependence of HB dynamics has some similarities with local density and residence dynamics, corresponding to very short length scales. Moreover, the effect of mutual reorientation on HB dynamics seems to be more important than that of mutual diffusion. Finally, the reorientational dynamics of several intramolecular vectors of ethanol have been systematically studied. From the results obtained, we may observe that the dynamics of several reorientational modes in the molecule exhibit significant differences between them. Furthermore, the effect of the HB state of each molecule on these dynamics has also been studied, revealing significant differences, especially in the case of the dynamics of HB free molecules.

  • Dynamics of water nanodroplets and aqueous protons in non-ionic reverse micelles

     RODRIGUEZ, J; Laria, D; Guardia Manuel, Elvira; Marti Rabassa, Jordi
    Physical chemistry chemical physics
    Vol. 11, num. 10, p. 1484-1490
    Date of publication: 2009-03
    Journal article

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    Molecular dynamics simulations of supercritical water confined within a carbon-slit pore  Open access

     Marti Rabassa, Jordi; Guardia Manuel, Elvira; Gordillo Bargueño, Maria Carmen; Sala2 Viñas, Jonàs
    Physical review E: statistical, nonlinear, and soft matter physics
    Vol. 79, num. 3, p. 031606-1-031606-10
    DOI: 10.1103/PhysRevE.79.031606
    Date of publication: 2009-03
    Journal article

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    We report the results of a series of molecular dynamics simulations of water inside a carbon-slit pore at supercritical conditions. A range of densities corresponding from liquid 0.66 g cm−3 to gas environments 0.08 g cm−3 at the supercritical temperature of 673 K were considered. Our findings are compared with previous studies of liquid water confined in graphene nanochannels at ambient and high temperatures, and indicate that the microscopic structure of water evolves from hydrogen bond networks characteristic of hot dense liquids to looser arrangements where the dominant units are water monomers and dimers. Water permittivity was found to be very small at low densities, with a tendency to grow with density and to reach typical values of unconfined supercritical water at 0.66 g cm−3 . In supercritical conditions, the residence time of water at interfaces is roughly similar to that of water in the central regions of the slabs, if the size of the considered region is taken into account. That time span is long enough to compute dynamical properties such as diffusion or spectral densities. Water diffusion in supercritical states is much faster at low densities, and it is produced in such a way that, at interfaces, translational diffusion is mainly produced along planes parallel to the carbon walls. Spectral frequency shifts depend on several factors, being temperature and density effects the most relevant. However, we can observe corrections due to confinement, important both at the graphene interface and in the central region of the water slab.

  • Liquid water confined in graphene nanochannels at supercritical conditions

     Guardia Manuel, Elvira; Marti Rabassa, Jordi; Sala2 Viñas, Jonàs
    Congreso de Física Estadística
    p. 161
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  • Liquid and supercritical water confined in graphene nanochannels

     Marti Rabassa, Jordi; Gordillo Bargueño, Maria Carmen; Guardia Manuel, Elvira; Sala2 Viñas, Jonàs
    EMLG/JMLG Annual Meeting. Understanding Solvation from Liquid to Supercritical Conditions
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  • Solvation dynamics of Coumarine-153 within beta-cyclodextrins in aqueous solution

     Guardia Manuel, Elvira; Laria, D; Marti Rabassa, Jordi; Rodrígues, J
    7th Liquid Matter Conference
    p. 1
    Presentation's date: 2008-06-27
    Presentation of work at congresses

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  • Water confined inside graphite nanochannels: a molecular dynamics simulation study

     Guardia Manuel, Elvira; Marti Rabassa, Jordi; Gordillo, J Martí M C G Nagy; Sala2 Viñas, Jonàs
    7th Liquid Matter Conference
    p. 1
    Presentation's date: 2008-06-27
    Presentation of work at congresses

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  • Exploring the Picosecond Time Domain of the Solvation Dynamics of Coumarin 153 within beta-Cyclodextrins

     RODRIGUEZ, J; Marti Rabassa, Jordi; Guardia Manuel, Elvira; Laria, D
    Journal of physical chemistry B
    Vol. 112, num. 30, p. 8990-8998
    Date of publication: 2008-07
    Journal article

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  • Supercritical water confined in graphene nanochanels

     Guardia Manuel, Elvira; Marti Rabassa, Jordi; Sala2 Viñas, Jonàs
    11th European Meeting on Supercritical Fluids. New Perspectives in Supercritical Fluids: Nanoscience, Materials and Processing
    p. 1-6
    Presentation's date: 2008-05-05
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  • Special issue - Selected papers on Molecular Liquids presented at the Annual Meeting of the EMLG/JMLG 2006, held in Barcelona, Spain - Preface

     Guardia Manuel, Elvira
    Journal of molecular liquids
    Vol. 136, num. 3, p. 183
    Date of publication: 2007-12
    Journal article

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  • Protons in non-ionic aqueous reverse micelles

     Marti Rabassa, Jordi; Guardia Manuel, Elvira; Rodríguez, J; Laria, D
    Journal of physical chemistry B
    Vol. 111, num. 17, p. 4432-4439
    Date of publication: 2007-05
    Journal article

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  • Liquid water confined in carbon nanochannels at high temperatures

     Marti Rabassa, Jordi; Guardia Manuel, Elvira; Nagy, G; Gordillo Bargueño, Maria Carmen
    Journal of physical chemistry B
    Vol. 111, num. 43, p. 12524-12530
    Date of publication: 2007-11
    Journal article

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  • Simulació per ordinador en matèria condensada. (Grup de recerca consolidat)

     Sese Castel, Gemma; Guardia Manuel, Elvira; Rey Oriol, Rosendo; Marti Rabassa, Jordi; Trullàs Simó, Joaquim
    Competitive project

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  • Simulación por ordenador de sistemas condensados: sales fundidas, disoluciones iónicas y líquidos moleculares

     Sese Castel, Gemma; Guardia Manuel, Elvira; Rey Oriol, Rosendo; Marti Rabassa, Jordi; Trullàs Simó, Joaquim
    Competitive project

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  • Special Issue EMLG/JMLG2006. Journal of molecular liquids

     Guardia Manuel, Elvira
    Vol. 136, num. 3
    Collaboration in journals

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  • ARMARI RACK; CLUSTER GIGABIT; SWITCH GIGABIT; CONSOLA

     Guardia Manuel, Elvira
    Competitive project

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  • Water confined in narrow slit graphite channels

     Marti Rabassa, Jordi; Guardia Manuel, Elvira; Gordillo Bargueño, Maria Carmen; Nagy, G
    EMLG/JMLG Annual Meeting: Liquid Systems under Extrem Conditions
    p. 24
    Presentation of work at congresses

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  • Molecular dynamics simulations of aqueous NaCI solutions at supercritical conditions: effects of ion concentration on the collective dynamic properties

     Guardia Manuel, Elvira
    Congreso de Física Estadística
    Presentation's date: 2006-09-14
    Presentation of work at congresses

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  • Protons in supercritical water: a multistate empirical valence bond study

     Marti Rabassa, Jordi; Guardia Manuel, Elvira; Laria, D
    EMLG/JMLG Annual Meeting: Liquid Systems under Extrem Conditions
    p. 4
    Presentation of work at congresses

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  • Molecular simulation of liquid water confined inside graphite channels: thermodynamics and structural properties

     Marti Rabassa, Jordi; Nagy, G; Gordillo Bargueño, Maria Carmen; Guardia Manuel, Elvira
    Journal of chemical physics
    Vol. 124-9, num. 094703, p. 1-7
    Date of publication: 2006-03
    Journal article

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