arXiv subjects

V. M. Trejos

Publications and source records attributed to V. M. Trejos.

4 recordsLinked to original sources

arXiv2026

Molecular dynamics study of perchloric acid using the extended Madrid-2019 force field

Perchloric acid (HClO$_4$) is widely used to prepare perchlorate salts with applications in propellants, industry, environmental chemistry, and biology. In this work, we used the intermolecular parameters from the extended Madrid-2019 force field for the perchlorate anion (ClO$_4^-$) and the oxonium cation (H$_3$O$^+$) together with TIP4P/2005 water to model perchloric acid solutions. The force field uses scaled charges of $\pm0.85e$ for monovalent ions and has been widely applied for aqueous ionic systems. We used the model to predict thermodynamic properties [densities and temperatures of maximum in density (TMD)], structural features (ion-water correlations: ion-hydrogen and ion-oxygen), and transport properties (self-diffusion coefficients and viscosity) of perchloric acid solutions at several concentrations. Experimental densities are predicted in excellent agreement up to 10 $m$. We also performed molecular simulations over a wide range of temperatures in order to determine the TMD of perchloric acid at different molalities. Predicted viscosities at 298.15 K and 1 bar are in good agreement with experimental data for concentrations below 4 $m$. Results are discussed in terms of model strengths and limitations.

physics.chem-ph↗

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.

cond-mat.soft↗

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.

cond-mat.soft↗

arXiv2018

Vapor-liquid equilibrium and equation of state of two-dimensional fluids from a discrete perturbation theory

The interest in the description of the properties of fluids of restricted dimensionality is growing for theoretical and practical reasons. In this work, we have firstly developed an analytical expression for the Helmholtz free energy of the two-dimensional square-well fluid in the Barker--Henderson framework. This equation of state is based on an approximate analytical radial distribution function for $d$-dimensional hard-sphere fluids ($1\leq d\leq 3$) and is validated against existing and new simulation results. The so-obtained equation of state is implemented in a discrete perturbation theory able to account for general potential shapes. The prototypical Lennard-Jones and Yukawa fluids are tested in its two-dimensional version against available and new simulation data with semi-quantitative agreement.

physics.chem-ph↗