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Dynamics of Surfactant Clustering at Interfaces and Its Influence on the Interfacial Tension: Atomistic Simulation of a Sodium Hexadecane-Benzene Sulfonate-Tetradecane-Water System

Paredes, Ricardo; Fariñas Sánchez, Ana Isabe; Medina Rodrĺguez, Bryan; Samaniego, Samantha; Aray, Yosslen; Álvarez, Luis Javier (2018)

The process of equilibration of the tetradecane-water interface in the presence of sodium hexadecane-benzene sulfonate is studied using intensive atomistic molecular dynamics simulations. Starting as an initial point with ...
Exploring the effect of the O -(1-heptylnonyl) benzene sulfonate surfactant on the nature of the linear hydrocarbons/water interface by means of an atomistic molecular dynamics simulation

Aray, Yosslen; Parra, José Gregorio; Jiménez, Doris Marianela; Paredes, Ricardo; Matiz, Alejandro; Samaniego, Samantha (2017)

Using molecular dynamics simulations a systematic study of the binding energy per cross sectional area for the water/n-alkane (hexane, octane, decane, dodecane and tetradecane) interfaces was performed. The effect of the ...
Exploring the electron density localization in MoS2 nanoparticles using a localized-electron detector: Unraveling the origin of the one-dimensional metallic sites on MoS2 catalysts

Aray, Yosslen; Barrios, Antonio Díaz (2018)

The nature of the electron density localization in two MoS2 nanoclusters containing eight rows of Mo atoms, one with 100% sulphur coverage at the Mo edges (n8-100S) and the other with 50% coverage (n8-50S) was studied using ...
Exploring the electron density localization in single MoS2 monolayers by means of a localize-electrons detector and the quantum theory of atoms in molecules

Aray, Yosslen (2017)

The nature of the electron density localization in a MoS2 monolayer under 0 % to 11% tensile strain has been systematically studied by means of a localized electron detector function and the Quantum Theory of atoms in ...
Exploring the nature of the H-bonds between the human class II MHC protein, HLA-DR1 (DRB*0101) and the influenza virus hemagglutinin peptide, HA306-318, using the quantum theory of atoms in molecules

Aray, Yosslen; Aguilera García, Ricardo; Izquierdo, Daniel (2019)

The nature of the H-bonds between the human protein HLA-DR1 (DRB*0101) and the hemagglutinin peptide HA306-318 has been studied using the Quantum Theory of Atoms in Molecules for the first time. We have found four H-bond ...
Nature of the Active Sites of Molybdenum-Based Catalysts and Their Interaction with Sulfur- and Nitrogen-Containing Molecules Using the Quantum Theory of Atoms in Molecules and the Molecular Electrostatic Potentia

Aray, Yosslen (2019)

Density-functional theory (DFT), morphologic, and quantum theory of atoms in molecules (QTAIM) studies of bilayer models of nonhydrogenated MoS2, CoMoS, and NiMoS phases have been performed. The QTAIM calculations have ...
On the electron density localization in elemental cubic ceramic and FCC transition metals by means of a localized electrons detector

Aray, Yosslen; Paredes, Ricardo; Alvarez, Luis Javier; Martiz, Alejandro (2017)

The electron density localization in insulator and semiconductor elemental cubic materials with diamond structure, carbon, silicon, germanium, and tin, and good metallic conductors with face centered cubic structure such ...
Structural and interfacial properties of the CO2-in-water foams prepared with sodium dodecyl sulfate (SDS): A molecular dynamics simulation study

Parra, José G.; Domínguez, Héctor; Aray, Yosslen; Iza, Peter; Zarate, Ximena; Schott, Eduardo (2019)

Structural characteristics, interfacial distribution and molecular interactions of the components of the CO2(gas)/ SDS/water/SDS/CO2(gas) systems as a function of the CO2(gas)/water interface coverage by the SDS surfactant ...

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Dynamics of Surfactant Clustering at Interfaces and Its Influence on the Interfacial Tension: Atomistic Simulation of a Sodium Hexadecane-Benzene Sulfonate-Tetradecane-Water System
...
Paredes, Ricardo | 2018

The process of equilibration of the tetradecane-water interface in the presence of sodium hexadecane-benzene sulfonate is studied using intensive atomistic molecular dynamics simulations. Starting as an initial point with all of the surfactants at the interface, it is obtained that the equilibration time of the interface (several microseconds) is orders of magnitude higher than previously reported simulated times. There is strong evidence that this slow equilibration process is due to the aggregation of surfactants molecules on the interface. To determine this fact, temporal evolution of interfacial tension and interfacial formation energy are studied and their temporal variations are correlated with cluster formation. To study cluster evolution, the mean cluster size and the probability that a molecule of surfactant chosen at random is free are obtained as a function of time. Cluster size distribution is estimated, and it is observed that some of the molecules remain free, whereas the rest agglomerate. Additionally, the temporal evolution of the interfacial thickness and the structure of the surfactant molecules on the interface are studied. It is observed how this structure depends on whether the molecules agglomerate or not.

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Exploring the effect of the O -(1-heptylnonyl) benzene sulfonate surfactant on the nature of the linear hydrocarbons/water interface by means of an atomistic molecular dynamics simulation
...
Aray, Yosslen | 2017

Using molecular dynamics simulations a systematic study of the binding energy per cross sectional area for the water/n-alkane (hexane, octane, decane, dodecane and tetradecane) interfaces was performed. The effect of the Sodium p-(1-heptylnonyl) benzene sulfonate surfactant, on the adhesion forces of the water/n-hydrocarbon (decane, undecane, dodecane, and tetradecane) interfaces was studied. Scanning of the binding energy per area against n-alkanes shows that the magnitude of this parameter for the surfactant tail-alkane interactions at the interface systematically increases with the chain length of the alkane, whereas it shows a maximum at undecane for the water-surfactant head interactions at the interface. This maximum of head adhesion forces thus agrees with the reported minimum value of the interfacial tension at undecane for the p-(1-heptylnonyl) benzene sulfonate, suggests that for the water/alkane interface it is this trend in surfactant head adhesion at the interface that defines that interfacial tension minimum value.

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Exploring the electron density localization in MoS2 nanoparticles using a localized-electron detector: Unraveling the origin of the one-dimensional metallic sites on MoS2 catalysts
...
Aray, Yosslen | 2018

The nature of the electron density localization in two MoS2 nanoclusters containing eight rows of Mo atoms, one with 100% sulphur coverage at the Mo edges (n8-100S) and the other with 50% coverage (n8-50S) was studied using a localized-electron detector function defined in the local moment representation. For n8-100S, pairs of neighboring S2 dimers cover the edges and the electron density localization function analysis shows the presence of a local triangular-shaped ring zone of highly delocalized electrons along these edges, which corresponds to a good metallic conductor zone. The optimized geometry analysis shows that the Mo-S2 bond length is much longer than that of the Mo-S bonds inside the cluster. The removal of one S atom from each sulphur dimer to create a cluster with 50% coverage produces a general compressive stress on the cluster optimized geometry, which shortens the Mo-S bond length, particularly at the edge. The electron density location function analysis shows that close to the cluster corners, a zone of highly delocalized electron zones with a characteristic semiconductor pattern and broken one-dimensional metallic ring was generated. These results suggest that the Mo-S2 bond elongation produced by the sulphur dimers is similar to a MoS2 monolayer under tensile strain and is the origin of the one-dimensional metallic sites at the Mo-edges. In general, the present findings show excellent agreement with the key features of the reported ambient pressure X-ray photoemission spectra and the corresponding simulated scanning tunneling microscopy images.

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Exploring the electron density localization in single MoS2 monolayers by means of a localize-electrons detector and the quantum theory of atoms in molecules
...
Aray, Yosslen | 2017

The nature of the electron density localization in a MoS2 monolayer under 0 % to 11% tensile strain has been systematically studied by means of a localized electron detector function and the Quantum Theory of atoms in molecules. At 10% tensile strain, this monolayer become metallic. It was found that for less than 6.5% of applied stress, the same atomic structure of the equilibrium geometry (0% strain) is maintained; while over 6.5% strain induces a transformation to a structure where the sulfur atoms placed on the top and bottom layer form S2 groups. The localized electron detector function shows the presence of zones of highly electron delocalization extending throughout the Mo central layer. For less than 10% tensile strain, these zones comprise the BCPs and the remainder CPs in separates regions of the space; while for the structures beyond 10% strain, all the critical points are involved in a region of highly delocalized electrons that extends throughout the material. This dissimilar electron localization pattern is like to that previously reported for semiconductors such as Ge bulk and metallic systems such as transition metals bulk. © 2017 Author(s).

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Exploring the nature of the H-bonds between the human class II MHC protein, HLA-DR1 (DRB*0101) and the influenza virus hemagglutinin peptide, HA306-318, using the quantum theory of atoms in molecules
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Aray, Yosslen | 2019

The nature of the H-bonds between the human protein HLA-DR1 (DRB*0101) and the hemagglutinin peptide HA306-318 has been studied using the Quantum Theory of Atoms in Molecules for the first time. We have found four H-bond groups: one conventional CO··HN bond group and three nonconventional CO··HC, π··HC involving aromatic rings and HN··HC aliphatic groups. The calculated electron density at the determined H-bond critical points suggests the follow protein pocket binding trend: P1 (2,311) >> P9 (1.109) > P4 (0.950) > P6 (0.553) > P7 (0.213) which agrees and reveal the nature of experimental findings, showing that P1 produces by a long way the strongest binding of the HLA-DR1 human protein molecule with the peptide backbone as consequence of the vast number of H-bonds in the P1 area and at the same time the largest specific binding of the peptide Tyr308 residue with aromatic residues located at the binding groove floor. The present results suggest the topological analysis of the electronic density as a valuable tool that allows a non-arbitrary partition of the pockets binding energy via the calculated electron density at the determined critical points.

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Nature of the Active Sites of Molybdenum-Based Catalysts and Their Interaction with Sulfur- and Nitrogen-Containing Molecules Using the Quantum Theory of Atoms in Molecules and the Molecular Electrostatic Potentia
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Aray, Yosslen | 2019

Density-functional theory (DFT), morphologic, and quantum theory of atoms in molecules (QTAIM) studies of bilayer models of nonhydrogenated MoS2, CoMoS, and NiMoS phases have been performed. The QTAIM calculations have shown that for inactive catalysts, such as MoS2 and Ni3S2, the basins of the outermost atoms of the particles on the exposed surfaces are almost covered by S atomic basins, giving reduced access to the Ni and Mo atoms. In contrast, for very active catalysts, such as NiMoS and RuS2, there are substantial open zones on the outermost S basin, giving considerable access to the metal atoms. Analysis of the electrostatic potential mapping onto the outermost atoms basins reveals soft Lewis acid zones for Ni3S2 and MoS2 and strong Lewis acid zones for NiMoS and RuS2. QTAIM and electrostatic potential calculations on hydrated MoS2-based monolayers have shown that the adsorption strengths (binding energies) of sulfur (H2S, thiophene, dibenzothiophene) and nitrogen (NH3 and acridine) compounds on the exposed metallic sites are related to the Lewis basic-acid interaction of the minima at the molecule and the maxima at the metallic sites, whereas on the so-called BRIM sites, it is the result of the combination of Lewis and Brønsted acidity. The studied nitrogen and sulfur molecules exhibit just one and two lone pairs on the N and S atoms, respectively. In general, N minima ≫ S minima, showing the origin of the larger adsorption of the organonitrogen molecules, except on those metallic sites where both sulfur lone pairs adsorb at two neighboring metal maxima. The present results corroborate and explain the origin of the reported DFT findings.

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On the electron density localization in elemental cubic ceramic and FCC transition metals by means of a localized electrons detector
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Aray, Yosslen | 2017

The electron density localization in insulator and semiconductor elemental cubic materials with diamond structure, carbon, silicon, germanium, and tin, and good metallic conductors with face centered cubic structure such as α-Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au, was studied using a localized electrons detector defined in the local moment representation. Our results clearly show an opposite pattern of the electron density localization for the cubic ceramic and transition metal materials. It was found that, for the elemental ceramic materials, the zone of low electron localization is very small and is mainly localized on the atomic basin edges. On the contrary, for the transition metals, there are low-valued localized electrons detector isocontours defining a zone of highly delocalized electrons that extends throughout the material. We have found that the best conductors are those in which the electron density at this low-value zone is the lowest.

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Structural and interfacial properties of the CO2-in-water foams prepared with sodium dodecyl sulfate (SDS): A molecular dynamics simulation study
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Parra, José G. | 2019

Structural characteristics, interfacial distribution and molecular interactions of the components of the CO2(gas)/ SDS/water/SDS/CO2(gas) systems as a function of the CO2(gas)/water interface coverage by the SDS surfactant to different amounts of the CO2 were studied with molecular dynamics simulations and the NVT ensemble. Initially, the repulsive nonbonding parameter between the water oxygen and CO2 oxygen was adjusted to improve the prediction of the solvation free energy, solubility of the CO2 gas in water and the behavior of the CO2(gas)/SDS/water/SDS/CO2(gas) systems at molecular level. Our results show that the stability of the studied foams can be improved incrementing of the vapor/water interface coverage with the SDS surfactant and the amount of CO2 in the system. With the highest interface coverage, the sulfate group has a molecular array more compact at the interface. Furthermore, CO2 gas have a reduction of the diffusion across of the hydrocarbon chains to the water layer with an increment of the number of CO2 molecules in the system, indicating a behavior more hydrophobic of the CO2 gas. The tendencies obtained of the simulations are consistent with the reported experimental results.

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Browsing by Author "Aray, Yosslen"

Dynamics of Surfactant Clustering at Interfaces and Its Influence on the Interfacial Tension: Atomistic Simulation of a Sodium Hexadecane-Benzene Sulfonate-Tetradecane-Water System ﻿

Exploring the effect of the O -(1-heptylnonyl) benzene sulfonate surfactant on the nature of the linear hydrocarbons/water interface by means of an atomistic molecular dynamics simulation ﻿

Exploring the electron density localization in MoS2 nanoparticles using a localized-electron detector: Unraveling the origin of the one-dimensional metallic sites on MoS2 catalysts ﻿

Exploring the electron density localization in single MoS2 monolayers by means of a localize-electrons detector and the quantum theory of atoms in molecules ﻿

Exploring the nature of the H-bonds between the human class II MHC protein, HLA-DR1 (DRB*0101) and the influenza virus hemagglutinin peptide, HA306-318, using the quantum theory of atoms in molecules ﻿

Nature of the Active Sites of Molybdenum-Based Catalysts and Their Interaction with Sulfur- and Nitrogen-Containing Molecules Using the Quantum Theory of Atoms in Molecules and the Molecular Electrostatic Potentia ﻿

On the electron density localization in elemental cubic ceramic and FCC transition metals by means of a localized electrons detector ﻿

Structural and interfacial properties of the CO2-in-water foams prepared with sodium dodecyl sulfate (SDS): A molecular dynamics simulation study ﻿

Envíos recientes

Dynamics of Surfactant Clustering at Interfaces and Its Influence on the Interfacial Tension: Atomistic Simulation of a Sodium Hexadecane-Benzene Sulfonate-Tetradecane-Water System

Exploring the effect of the O -(1-heptylnonyl) benzene sulfonate surfactant on the nature of the linear hydrocarbons/water interface by means of an atomistic molecular dynamics simulation

Exploring the electron density localization in MoS2 nanoparticles using a localized-electron detector: Unraveling the origin of the one-dimensional metallic sites on MoS2 catalysts

Exploring the electron density localization in single MoS2 monolayers by means of a localize-electrons detector and the quantum theory of atoms in molecules

Exploring the nature of the H-bonds between the human class II MHC protein, HLA-DR1 (DRB*0101) and the influenza virus hemagglutinin peptide, HA306-318, using the quantum theory of atoms in molecules

Nature of the Active Sites of Molybdenum-Based Catalysts and Their Interaction with Sulfur- and Nitrogen-Containing Molecules Using the Quantum Theory of Atoms in Molecules and the Molecular Electrostatic Potentia

On the electron density localization in elemental cubic ceramic and FCC transition metals by means of a localized electrons detector

Structural and interfacial properties of the CO2-in-water foams prepared with sodium dodecyl sulfate (SDS): A molecular dynamics simulation study

Dynamics of Surfactant Clustering at Interfaces and Its Influence on the Interfacial Tension: Atomistic Simulation of a Sodium Hexadecane-Benzene Sulfonate-Tetradecane-Water System

Exploring the effect of the O -(1-heptylnonyl) benzene sulfonate surfactant on the nature of the linear hydrocarbons/water interface by means of an atomistic molecular dynamics simulation

Exploring the electron density localization in MoS2 nanoparticles using a localized-electron detector: Unraveling the origin of the one-dimensional metallic sites on MoS2 catalysts

Exploring the electron density localization in single MoS2 monolayers by means of a localize-electrons detector and the quantum theory of atoms in molecules

Exploring the nature of the H-bonds between the human class II MHC protein, HLA-DR1 (DRB*0101) and the influenza virus hemagglutinin peptide, HA306-318, using the quantum theory of atoms in molecules

Nature of the Active Sites of Molybdenum-Based Catalysts and Their Interaction with Sulfur- and Nitrogen-Containing Molecules Using the Quantum Theory of Atoms in Molecules and the Molecular Electrostatic Potentia

On the electron density localization in elemental cubic ceramic and FCC transition metals by means of a localized electrons detector

Structural and interfacial properties of the CO2-in-water foams prepared with sodium dodecyl sulfate (SDS): A molecular dynamics simulation study