Jacqueline Quintana

• PhD
• National Autonomous University of Mexico

The ability to tailor effective interactions at the molecular level to provide a platform to create advanced functional materials is a challenge for the scientific community. The main goal is to develop a good interaction potential model driving the formation of a given set of target structures. In this work, we propose a simple method to design in...

Colloids of nanometric size dispersed in a nematic environment are simulated using a hybrid algorithm that combines rules from Multi-particle Collision Dynamics and Molecular Dynamics. Coupling between flow and orientation fields is incorporated through the application of the Leslie–Ericksen theory for reorientation of slender rods under flow. It i...

Hierarchical self-assembly of soft matter provides a powerful route to create complex materials with enhanced physical properties. The understanding of the fundamental processes leading to such organization can provide design rules to create new functional materials. In this work, we use a simple model of polymer-grafted nanoparticles to explore th...

In this work, a molecular simulation study of confined hard-spheres particles with square-well (SW) attractive interactions with two and four associating SW sites based on the first-order perturbation form of Wertheim’s theory is presented. An extended version of the Gibbs ensemble technique for inhomogeneous fluids [A. Z. Panagiotopoulos, Mol. Phy...

Small alterations in the molecular details may produce noticeable changes in the symmetry of the resulting phase behavior. It is possible to produce morphologies having different n-fold symmetries by manipulating molecular features such as chirality, polarity or anisotropy. In this paper, a two dimensional hard molecular model is introduced to stud...

A vibrating version of patchy particles in two dimensions is introduced to study self-assembly of kagome lattices, disordered networks of looping structures, and linear arrays. Discontinuous Molecular Dynamics simulations in the canonical ensemble are used to characterize the molecular architectures and termodynamic conditions that result in each o...

Short ranged potentials and their anisotropy produce spontaneous chiral resolution in a two dimensional model of patchy particles introduced in this paper. This model could represent an equimolar binary mixture (racemic mixture) of two kinds of chiral molecules (enantiomers) adsorbed to a bi-dimensional domain where only lateral short ranged intera...

Chiral segregation and liquid crystalline aggregates in two dimensions are studied for a heterochiral mixture of oversimplified versions of so called hockey stick-shaped particles, made with two line segments that interact via an infinitely repulsive potential. The goal of this study is to explore the possibility of producing chiral segregation and...

The phase behavior of a two-dimensional square-well model of width 1.5σ, with emphasis on the low-temperature and/or high-density region, is studied using Monte Carlo simulation in the canonical and isothermal-isobaric ensembles, and discontinuous molecular-dynamics simulation in the canonical ensemble. Several properties, such as equations of stat...

The map of low and high density phases of an idealized system, the infinitely hard zigzag line model with two Lennard-Jones (LJ) sites is presented. LJ sites are added to a previous model composed of the infinitely hard zigzag line shape particles, R.A. Perusqía, J. Peón, J. Quintana, Physica A 345 (1) (2005) 130-142. The attractions and the molecu...

Liquid-vapor coexistence and interfacial properties of short lineal rigid vibrating chains with three tangent monomers in two and three dimensions are calculated. The effect of the range and position of a long ranged square well attractive potential is studied. Orthobaric densities, vapor pressures, surface tensions, and interfacial widths are repo...

The effect of flexibility on liquid-vapor and interfacial properties of tangent linear vibrating square well chains is studied. Surface tension, orthobaric densities, vapor pressures, and interfacial thicknesses are reported and analyzed using corresponding states principles. Discontinuous molecular dynamics simulations in two and three dimensions...

The phase behavior of a two-dimensional hard-particle model is studied via Monte Carlo simulations using the grand canonical, the isobaric and the canonical ensembles. This model consists of a three-segmented line whose geometry resembles a bow shape. The model reduces to some limiting cases: hard needles and bent-core particles. Manipulating the m...

Liquid-vapor coexistence and interfacial properties of square wells in two dimensions are calculated. Orthobaric densities, vapor pressures, surface tensions, and interfacial thicknesses are reported. Results are presented for a series of potential widths λ∗ = 1.4, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, and 5, where λ∗ is given in units of the hard core diam...

Phase transitions and structural properties of the two-dimensional systems of hockey stick-shaped molecules have been examined by means of Monte Carlo simulations and the Onsager-theory. The hockey stick-shaped particles are modeled as hard bent-core needles. Isotropic–nematic and nematic–smectic antiferroelectric structural changes are observed. S...

Spontaneously deformed nematic and antiferroelectric smectic structures have been detected in a two-dimensional system of hard banana-shaped needles by means of Monte Carlo simulation and Onsager theory. The spatially non-uniform and deformed nematic consists of orientationally ordered polar domains, where the nematic director displays mainly bende...

The mesophases of two infinitely hard models with chiral and anisotropic characteristics in two dimensions are studied. Evidence for nematic and smectic behavior is provided via Monte Carlo simulations using restrictive values of the molecular parameters. Both models are geometrically chiral; one has polar structure. The concept of smectic phase co...

The orientational and positional ordering of the two-dimensional system of hard zigzag particles has been investigated by means of Onsager theory. Analytical results are obtained for the transition densities of the isotropic-nematic and the nematic-smectic phase transitions. It is shown that the stability of the nematic and smectic phases is very s...

A model for the stochastic evolution of a linear paramagnetic system in contact with a thermal bath and subjected to variations in time of an external magnetic field, H, is presented. Changes in the Hamiltonian of this system, , defined through the relation , are considered for the special case in which the external field is varied from an initial...

We present the phase diagram of Gay-Berne potential for discotic symmetry using a particular set of parameters. We show evidence of isotropic, nematic and columnar phases. These results were obtained using two different Molecular Dynamics ensembles to get complementary information. The canonical ensemble to produce interphases between coexisting ph...

Assuming the aggregates of a single chiral component as a pure phase, chiral segregation can be considered as a coexistence of two phases, therefore the formalisms of phase transitions in Statistical Mechanics can be applied. That is, chiral segregation can be considered as phase equilibrium. The standard mechanism to understand phase equilibrium c...

The distribution functions of the work performed on a two-dimensional Ising model under the influence of an external magnetic field which is switched on and off are studied. These distributions are calculated by means of Monte Carlo simulations for temperatures below and above, as well as close to the critical temperature, Tc, and for different rat...

The liquid crystalline behavior of a two dimensional (2D) model of hard needles bent into a "zigzag shape" is studied. This model, originally designed to study two dimensional chiral segregation, also shows liquid crystalline behavior and has some anomalous features which are contrasted in relation to the following: (i) Most of the microscopical mo...

We study the statistical mechanical conditions under which segregation of racemic mixtures of chiral molecules is possible in a two-dimensional fluid model. Motivated by experimental evidence indicating that chiral hydrophilic heads of amphiphilic molecules lying in a monolayer can crystallize undergoing a chiral phase separation, we propose a two-...

The differences between the phase diagram of the Gay-Berne potential confined by two identical walls versus the corresponding bulk phase diagram have been investigated. A wall-fluid interaction 9-3 Lennard-Jones potential was used. The study was performed in most cases by using the hybrid Monte Carlo method for the muVT ensemble. Several isotherms...

As an illustration of the unfolding of scale invariance in stochastic and statistical mechanical systems we consider some properties of random-walks with long-tailed step distributions. We analyze how a renormalization group (RG) transformation flows along maximum entropy step distributions under a given constrained moment and ends at a fixed-point...

We describe the modifications undergone by phase transitions associated with a planar surface when the system is confined by the presence of a second surface parallel to the first. The inhomogeneous states are studied within the Landau density functional theory, which imparts scaling properties to the order parameter profiles. We distinguish betwee...

The concentration profiles and phase properties of symmetric fluid mixtures confined by parallel planar walls are analyzed for the cases of identical and symmetrically opposed fields at the walls. We focus on the occurrence of phase separation otherwise absent in bulk mixtures and find that this can take place when chemical potentials and molecular...

As an illustration of anomalous diffusion in sparsely connected systems we study the properties of a model of porous media characterized by a random fracture/pore network. The structural connectivity of the system is furnished by a long-ranged bond percolation model and transport throughout it is described by a corresponding long-tailed distributio...

En la termodinámica más tradicional cuando se estudian transiciones de fases de un sistema se consideran muestras macroscópicas. El interés acerca de las transiciones de fases de sistemas que no son macroscópicos en cuando menos una dirección (sistemas confinados) data desde mediados del siglo XIX cuando Lord Kelvin estudió el fenómeno. Sin embargo...

Some properties are described of the nucleation and the spinodal decomposition of a binary mixture in the neighbourhood of a three-phase coexistence state that exhibits complete wetting of one phase at the interface of the other two. A square-gradient density functional approach to inhomogeneities in only one spatial direction is applied, and an an...

We survey a collection of statistical-mechanical problems involving systems inhomogeneous (only) in one spatial direction and seldom discussed by way of a unified treatment. We employ a Landau density functional approach and present the analysis with the help of the equivalent nonlinear dynamical system. The different possible behaviors are visuali...

The consequences of confinement on the isotropic-nematic (IN) transition are investigated for a slab geometry with walls that compete in molecular alignment. We employ the Landau-de Gennes free energy with symmetrically opposing wall fields that favor random parallel and homeotropic orientations, respectively, at each wall, and describe the phase d...

Results for the density profile for Yukawa molecules near a hard wall and an exponential attractive wall are presented for Grand Canonical Monte Carlo (GCMC) simulations, for the singlet hypernetted chain (HNC) integral equation and for a modified version of the Lovett–Mou–Buff–Wertheim (LMBW-1) which uses the exact contact value theorem. The resul...

A review is given of some features of theories for inhomogeneous fluids of nonspherical molecules that take as input the direct correlation function of the corresponding homogeneous system. Two different methods are described for defining the structure of hard homonuclear molecules close to a hard planar wall. A spherical harmonics expanison (SHE)...

A comparison of Percus–Yevick–Pynn–Lado model theory and a density functional (DF) theory of nonuniform fluids of nonspherical particles is performed. The DF used is a new generalization of Tarazona’s theory. The conclusion is that DF theory provides a preferable route to describe the system under consideration. Its accuracy can be improved with be...

We present an application of a version of the density functional theory to describe the interphase of Lennard-Jones fluid in contact with a large sphere. A comparison of theory and Monte Carlo data is shown. The theory is generally good and becomes more satisfactory as the radius of the large sphere is increased.

The Percus–Yevick (PY) equation for inhomogeneous hard linear molecules is presented and solved. Calculations of the density profile are shown. Despite earlier failures of the PY approximation to predict some kinds of angular properties in homogeneous systems, here we find predictions which are qualitatively correct and quantitatively acceptable. I...

The excess Helmholtz free energy ΔA of two models of water, the revised central force model and the simple point charge model, has been calculated by molecular dynamics computer simulation. The method of “thermodynamic integration” has been used to calculate the free energy difference between the (model) water and an ideal gas of molecules at the s...

The Fischer-Methfessel approximation consists of approximating a pair correlation function of an inhomogeneous fluid by the corresponding homogeneous (bulk) correlation function evaluated with a locally averaged density. The averaging is done over a sphere of molecular dimensions. Using both the Born-Green and the Lovett-Mou-Buff-Wertheim equations...

The Lovett-Mou-Buff-Wertheim (LMBW) equation relating pair direct correlation functions with singlet density profiles is considered. If the direct correlation function is approximated by its bulk value, the LMBW equation becomes the hypernetted chain (HNC) approximation or, if linearized, the Percus-Yevick (PY) approximation. For a system of partic...