arXiv subjects

O. Pizio

Publications and source records attributed to O. Pizio.

At least 19 recordsLinked to original sources

arXiv2026

Pressure effects in the properties of simple monohydric alcohols. Lessons from molecular dynamics simulations of united atom type UAM-EW model

We explore the pressure dependence of a set of properties of simple monohydric alcohols, namely of methanol, ethanol and 1-propanol, by using isobaric-isothermal molecular dynamics computer simulations. A recently proposed united atom, non-polarizable force field for each of alcohols [V. Garc\'{i}a-Melgarejo et al., J. Mol. Liq., 323, 114576 (2021)] is applied. Accuracy of the force field is evaluated by comparing the simulation results and available experimental data from the literature. Specifically, the density of alcohols upon increasing pressure, the isothermal compressibility, the static dielectric constant and self-diffusion coefficient are investigated starting from 1 bar up to 3 kbar. Evolution of the microscopic structure under pressure is discussed in terms of the pair distribution functions and some coordination numbers. Conclusions of the present modelling and necessary developments to consider in future work are commented on.

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arXiv2026

II. Temperature trends in the properties of simple monohydric alcohols. Molecular dynamics simulations of united atom UAMI-EW model

We explore the dependence of a wide set of properties of monohydric alcohols on temperature by using the isobaric-isothermal molecular dynamics computer simulations. Namely, methanol (MeOH), ethanol (EtOH) and 1-propanol (PrOH) alcohols are studied. The recently proposed united atom, non-polarizable force field for each of alcohols [V. Garc\'{i}a-Melgarejo et al., J. Mol. Liq., 2021, 323, 114576] is applied for this purpose. Accuracy of the force field is discussed comparing predictions from simulations and experimental data for density, dielectric constant, surface tension, and self-diffusion coefficient. Supplementary insights concerning applicability of the model are obtained by exploration of the composition dependence of various properties for MeOH-PrOH mixtures. Peculiarities of mixing of species in this system are elucidated in terms of density, excess mixing volume and excess mixing enthalpy. Static dielectric constant of the mixture and the corresponding excess are obtained. Perspectives of modelling are commented finally.

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arXiv2025

Towards construction of microscopic model for smart coating of a solid surface

The density functional approach for classical associating fluids is used to explore the wetting phase diagrams for model systems consisting of water and graphite-like solid surfaces chemically modified by a small amount of grafted chain molecules. The water-like fluid model is adopted from the work of Clark et al. [Mol. Phys., 104, 3561 (2006)]. It very well describes the bulk water vapor-liquid coexistence. Each chain molecule consists of tangentially bonded hard sphere segments. We focus on the investigation of the growth of water film on such complex substrates and exploration of the wetting behavior. For grafted monomers, the prewetting phase diagrams are similar to the diagrams for water on a non-modified solid surface. However, for grafted trimers and pentamers, a physically much richer behavior is observed and analyzed. Trends of the behavior of the wetting temperature and the prewetting critical temperature on the grafting density and water-segments attraction are discussed in detail.

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arXiv2025

On the temperature, pressure and composition effects in the properties of water-methanol mixtures. I. Density, excess mixing volume and enthalpy, and self-diffusion coefficients from molecular dynamics simulations

We report the temperature, pressure and composition dependence of some basic properties of model liquid water-methanol mixtures. For this purpose the isobaric-isothermal molecular dynamics computer simulations are employed. Our principal focus is on the united atom non-polarizable UAM-I-EW model for methanol which was recently parametrized the paper by Garcia-Melgarejo et al. [J. Mol. Liq., 2021, 323, 114576], combined with the TIP4P/$\varepsilon$ water model. In perspective, the methanol model permits a convenient extension for other monohydric alcohols mixed with water. The behavior of density, excess mixing volume and enthalpy are described. Partial mixing properties are interpreted. Besides, we explored the trends of behavior of self-diffusion coefficients of the species of a mixture. The quality of predictions of the model is critically evaluated by detailed comparisons with experimental results. Various results are novel and provide new insights into the behavior of the mixtures in question at different temperatures and at high pressures. An improvement of the modelling necessary for further research is discussed.

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arXiv2024

Molecular dynamics simulations of water-ethanol mixtures. I. Composition trends in thermodynamic properties

We explored the composition dependence of a rather comprehensive set of properties of liquid water-ethanol mixtures by using the isobaric-isothermal molecular dynamics computer simulations. The united atom non-polarizable model from the TraPPE data basis for the ethanol molecule combined with the TIP4P-2005 and SPC/E water models is considered. We restrict our calculations to atmospheric pressure, 0.1013 MPa, and room temperature, 298.15 K. Composition trends of the behavior of density, excess mixing volume, apparent molar volumes are described. On the other hand, the excess mixing enthalpy and partial molar enthalpies of species are reported. Besides, we explore the coefficient of isobaric thermal expansion, isothermal heat capacity, adiabatic bulk modulus and heat capacity at constant pressure. In addition, the self-diffusion coefficients of species, the static dielectric constant and the surface tension are described. We intend to get insights into peculiarities of mixing of species in the mixture upon changes of ethanol molar fraction. The quality of predictions of the models is critically evaluated by detailed comparisons with experimental results. Then, necessary improvements of the modelling are discussed.

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arXiv2024

Revisiting the wetting behavior of solid surfaces by water-like models within a density functional theory

We perform the analysis of predictions of a classical density functional theory for associating fluids with different association strength concerned with wetting of solid surfaces. The four associating sites water-like models with non-associative square-well attraction parametrized by Clark et al. [Mol. Phys., 2006, 104, 3561] are considered. The fluid-solid potential is assumed to have a 10-4-3 functional form. The growth of water film on the substrate upon changing the chemical potential is described. The wetting and prewetting critical temperatures, as well as the prewetting phase diagram are evaluated for different fluid-solid attraction strength from the analysis of the adsorption isotherms. Moreover, the temperature dependence of the contact angle is obtained from the Young equation. It yields estimates for the wetting temperature as well. Theoretical findings are compared with experimental results and in a few cases with data from computer simulations. The theory is successful and quite accurate in describing the wetting temperature and contact angle changes with temperature for different values of fluid-substrate attraction. Moreover, the method provides an easy tool to study other associating fluids on solids of importance for chemical engineering, in comparison with laboratory experiments and computer simulations.

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arXiv2023

Aspects of the microscopic structure of curcumin solutions with water-dimethylsulfoxide solvent. Molecular dynamics computer simulation study

We explore some aspects of the microscopic structure of curcumin solutions with water-dimethylsulfoxide solvent of variable composition. Molecular dynamics computer simulations at isobaric-isothermal conditions are used for this purpose. The model consists of the OPLS-UA type model for the enol conformer of curcumin (J. Mol. Liq., 223, 707, 2016), the OPLS model for the dimethylsulfoxide (DMSO) and the SPC/E water model. Radial distributions for the centers of mass of curcumin molecules are evaluated and the corresponding running coordination numbers are analyzed. The disaggregation of curcumin clusters upon increasing the DMSO content in water-DMSO solvent is elucidated. Changes of the distribution of water and DMSO species around curcumin molecules are investigated. A qualitative comparison of our findings with the results of other authors is performed. A possibility to relate predictions of the model with the experimental observations in terms of the so-called critical wateraggregation percentage is discussed.

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arXiv2023

Structural aspects of the clustering of curcumin molecules in water. Molecular dynamics computer simulation study

We explore clustering of curcumin molecules in water by using the OPLS-UA model for the enol conformer of curcumin (J. Mol. Liq., 223, 707, 2016) and the SPC-E water model. With this purpose, solutions of 2, 4, 8, 12, 16 and 20 curcumin molecules in 3000 water molecules are studied by using extensive molecular dynamics computer simulations. Radial distributions for the centers of mass of curcumin molecules are evaluated and the running coordination numbers are analyzed. The formation of clusters on time is elucidated. The internal structure of molecules within the cluster is described by using radial distributions of the elements of the curcumin molecule, the orientation descriptors, the order parameter and the radius of gyration. The self-diffusion coefficient of solute molecules in clusters is evaluated. The distribution of water species around clusters is described in detail. A comparison of our findings with computer simulation results of other authors is performed. A possibility to relate predictions of the model with experimental observations is discussed.

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arXiv2023

Apparent molar volume anomaly in water-dimethyl sulfoxide liquid mixtures. Molecular dynamics computer simulations

We have studied the composition dependence of density of liquid water-DMSO mixtures at different temperatures by using the isobaric-isothermal (NPT) molecular dynamics computer simulations. The non-polarizable semi-flexible, P1 and P2 models for the DMSO molecule combined with the TIP4P-2005 water model are considered. The excess mixing volume and the apparent molar volumes of the species are reported. We have established that the P1-TIP4P-2005 model for the mixture provides a very good description of the location of the minimum of apparent molar volume for DMSO species indicating the anomaly. Most important is that the temperature interval where the hydrophobic effect exists, is correctly captured with this modelling, in contrast to the P2-TIP4P-2005 model.

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arXiv2022

Revisiting the composition dependence of the properties of water-dimethyl sulfoxide liquid mixtures. Molecular dynamics computer simulations

We have revisited the composition dependence of principal properties of liquid water-DMSO mixtures by using the isobaric-isothermal molecular dynamics computer simulations. A set of non-polarizable semi-flexible models for the DMSO molecule combined with the TIP4P-2005 and TIP4P/$\varepsilon$ water models is considered. We restrict calculations to atmospheric pressure, 0.1013 MPa, and room temperature, 298.15 K. Composition trends of density, excess mixing volume and excess mixing enthalpy, partial molar volumes and partial molar enthalpies of species, apparent molar volumes are reported. Besides, we explore composition trends of the self-diffusion of species, the static dielectric constant and the surface tension. Evolution of the microscopic structure of the mixture with composition is analyzed in terms of radial distributions functions, coordination numbers and the fractions of hydrogen-bonded molecules. We intend to capture the peculiarities of mixing the species in the mixture upon the DMSO molar fraction and the anomalous behaviors, if manifested in each of the properties under study. The quality of several combinations of the models for species is evaluated in detail to establish the possibility of necessary improvements.

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arXiv2022

Contact angle of water on a model heterogeneous surface. A density functional approach

We use a density functional approach to calculate the contact angle of the water model on a heterogeneous, graphite-like surface. The surface heterogeneity results from the pre-adsorption of a layer of spherical species. The pre-adsorbed molecules can also be a mixture of molecules of different sizes. The presence of pre-adsorbed layer causes geometrical and energetical heterogeneity of the surfaces. Two cases are considered. The pre-adsorbed molecules can either behave like hard-sphere obstacles, or they can also attract the molecules of water. In the first case, an increase of the amount of pre-adsorbed species leads to an increase of the wetting temperature, but this increase does not depend linearly on the amount of obstacles. In the case of obstacles exerting attractive forces on water molecules, the curves describing the dependence between the amount of pre-adsorbed species and the contact angle can exhibit a maximum. In addition, we have also studied how the pre-adsorbed species influence the local densities of gaseous and liquid phases in contact with a modified solid surface.

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arXiv2021

Tetrahedrality, hydrogen bonding and the density anomaly of the central force water model. A Monte Carlo study

Monte Carlo computer simulations in the canonical and grand canonical statistical ensemble were used to explore the properties of the central force (CF1) water model. The intramolecular structure of the H$_2$O molecule is well reproduced by the model. Emphasis was made on hydrogen bonding, and on the tehrahedral, $q$, and translational, $τ$, order parameters. An energetic definition of the hydrogen bond gives more consistent results for the average number of hydrogen bonds compared to the one-parameter distance criterion. At 300 K, an average value of 3.8 was obtained. The $q$ and $τ$ metrics were used to elucidate the water-like anomalous behaviour of the CF1 model. The structural anomalies lead to the density anomaly, with a good agreement of the model's density with the experimental $ρ(T)$ trends. The chemical potential-density projection of the model's equation of state was explored. Vapour-liquid coexistence was observed at sufficiently low temperatures.

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arXiv2021

Phase behavior of water-like models in nanoscopic pores of slit shape. Predictions from a density functional theory

We have explored the phase behavior of a set of water-like models in slit pores of nanoscopic dimensions. The interaction between water and pore walls mimics the graphite surface. A version of density functional method is used as theoretical tools. The fluid models are adopted from the work of Clark et al. [Mol. Phys., 2006, 104, 3561]. They reproduce the bulk water vapor-liquid coexistence envelope adequately. Our principal focus is on changes of topology of the phase diagram of confined water and establishing trends of behavior of the crossover temperature between condensation and evaporation on the strength of water-graphite interaction potential. Growth of the water film on the pore walls is illustrated in terms of the density profiles. Theoretical results are discussed in context of computer simulation findings for water models in pores.

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arXiv2021

On the apparent molar volume of methanol in water-methanol mixtures. Composition and temperature effects from molecular dynamics study

We explore the effects of composition and temperature on the apparent molar volumes of species of water-methanol mixtures. Isothermal-isobaric molecular dynamics simulations are used with this purpose. Several combinations of models for water and for methanol are explored. Validity of predictions concerned with a puzzling minimum of apparent molar volume of methanol in water-rich solutions is tested against experimental results.

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arXiv2020

On the properties of methanolic NaCl solution by molecular dynamics simulations

Isothermal-isobaric molecular dynamics simulations are used to examine the microscopic structure and principal thermodynamic properties of a model solution consisting of NaCl salt dissolved in methanol solvent. Four united atom force fields for methanol are involved. Concerning ion solutes we used the Joung-Cheatham, Smith-Dang models as well as the model from the laboratory of Vrabec. Our principal focus is to evaluate the quality of predictions of different combinations of models for basic properties of these solutions. Specifically, we explored the change of density on molality, the structural properties in terms of various pair distribution functions, the coordination numbers, the number of ion pairs and the average number of hydrogen bonds. In addition, changes of the self-diffusion coefficients of species, the solvent dielectric constant and the evolution of the surface tension with ion concentration are described.

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arXiv2020

Towards the description of water adsorption in slit-like nanochannels with grafted molecular brushes. Density functional theory

We have explored a model for adsorption of water into slit-like nanochannels with two walls chemically modified by grafted polymer layers forming brushes. A version of density functional method is used as theoretical tools. The water-like fluid model adopted from the work of Clark et al. [Mol. Phys., 2006, 104, 3561] adequately reproduces the bulk vapour-liquid coexistence envelope. The polymer layer consists of chain molecules in the framework of pearl-necklace model. Each chain molecule is chemically bonded to the pore walls by a single terminating segment. Our principal focus is in the study of the dependence of polymer layer height on grafting density and in the microscopic structure of the interface between adsorbed fluid and brushes. Thermal response of these properties upon adsorption is investigated in detail. The results are of importance to understand shrinking and swelling of the molecular brushes in the nanochannels.

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arXiv2019

Molecular dynamics simulations of the properties of water-methanol mixtures. Effects of force fields

Isothermal-isobaric molecular dynamics simulations are used to examine the microscopic structure and some properties of water-methanol liquid mixture. The TIP4P/2005 and SPC/E water models are combined with the united atom TraPPE and the all-atom force field model for methanol. Our principal focus is to evaluate the quality of predictions of different combinations of model force fields concerning the composition dependence of basic properties of this system. Specifically, we explored the composition effects on density, excess molar volume and excess entropy, as well as on the surface tension and static dielectric constant. In addition, the structural properties are described in terms of the coordination numbers and the average number of hydrogen bonds between molecules of constituent species. Finally, the composition dependence of self-diffusion coefficients of the species is evaluated. All theoretical predictions are tested with respect to experimental data.

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arXiv2018

Effects of ion concentration and solvent composition on the properties of water-methanol solutions of NaCl. NPT molecular dynamics computer simulation results

Isothermal-isobaric molecular dynamics simulations are used to examine the microscopic structure and other properties of a model solution consisting of NaCl salt dissolved in water-methanol mixture. The SPC/E water model and the united atom model for methanol are combined with the force field for ions by Dang [J. Amer. Chem. Soc., 1995, 117, 6954] to describe the entire system. Our principal focus is to study the effects of two variables, namely, the solvent composition and ion concentrations on the solution's density, on the structural properties, self-diffusion coefficients of the species and the dielectric constant. Moreover, we performed a detailed analysis of the first coordination numbers of the species. Trends of the behaviour of the average number of hydrogen bonds between solvent molecules are evaluated.

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