1,226 research outputs found
Solvent primitive model of an electric double layer in slit-like pores: microscopic structure, adsorption and capacitance from a density functional approach
We investigate the electric double layer formed between charged walls of a
slit-like pore and a solvent primitive model (SPM) for electrolyte solution.
The recently developed version of the weighted density functional approach for
electrostatic interparticle interaction is applied to the study of the density
profiles, adsorption and selectivity of adsorption of ions and solvent species.
Our principal focus, however, is in the dependence of differential capacitance
on the applied voltage, on the electrode and on the pore width. We discuss the
properties of the model with respect to the behavior of a primitive model,
i.e., in the absence of a hard-sphere solvent. We observed that the
differential capacitance of the SPM on the applied electrostatic potential has
the camel-like shape unless the ion fraction is high. Moreover, it is
documented that the dependence of differential capacitance of the SPM on the
pore width is oscillatory, which is in close similarity to the primitive model.Comment: 10 pages, 5 figure
On the composition dependence of the microscopic structure, thermodynamic, dynamic and dielectric properties of water-dimethyl formamide model mixtures. Molecular dynamics simulation results
Isothermal-isobaric molecular dynamics simulations have been performed to
examine an ample set of properties of the model water-N,N-dimethylformamide
(DMF) mixture as a function of composition. The SPC-E and TIP4P-Ew water models
together with two united atom models for DMF [Chalaris M., Samios J., J. Chem.
Phys., 2000, 112, 8581; Cordeiro J., Int. J. Quantum Chem., 1997, 65, 709] were
used. Our principal analyses concern the behaviour of structural properties in
terms of radial distribution functions, and the number of hydrogen bonds
between molecules of different species as well as thermodynamic properties.
Namely, we explore the density, excess mixing molar volume and enthalpy, the
heat capacity and excess mixing heat capacity. Finally, the self-diffusion
coefficients of species and the dielectric constant of the system are
discussed. In addition, surface tension of water-DMF mixtures has been
calculated and analyzed.Comment: 15 pages, 11 figure
On the properties of a single OPLS-UA model curcumin molecule in water, methanol and dimethyl sulfoxide. Molecular dynamics computer simulation results
The properties of model solutions consisting of a solute --- single curcumin
molecule in water, methanol and dimethyl sulfoxide solvents have been studied
using molecular dynamics (MD) computer simulations in the isobaric-isothermal
ensemble. The united atom OPLS force field (OPLS-UA) model for curcumin
molecule proposed by us recently [J. Mol. Liq., 2016, 223, 707] in combination
with the SPC/E water, and the OPLS-UA type models for methanol and dimethyl
sulfoxide have been applied. We have described changes of the internal
structure of the solute molecule induced by different solvent media in very
detail. The pair distribution functions between particular fragments of a
solute molecule with solvent particles have been analyzed. Statistical features
of the hydrogen bonding between different species were explored. Finally, we
have obtained a self-diffusion coefficient of curcumin molecules in three model
solvents.Comment: 20 pages, 17 figures, 4 table
Temperature dependence of the microscopic structure and density anomaly of the SPC/E and TIP4P-Ew water models. Molecular dynamics simulation results
We have investigated temperature trends of the microscopic structure of the
SPC/E and TIP4P-Ew water models in terms of the pair distribution functions,
coordination numbers, the average number of hydrogen bonds, the distribution of
bonding states of a single molecule as well as the angular distribution of
molecules by using the constant pressure molecular dynamics simulations. The
evolution of the structure is put in correspondence with the dependence of
water density on high temperatures down to the region of temperatures where the
system becomes supercooled. It is shown that the fraction of molecules with
three and four bonds determine the maximum density for both models. Moreover,
the temperature dependence of the dielectric constant is obtained and analyzed.Comment: 11 pages, 5 figure
Changes in the structure of tethered chain molecules as predicted by density functional approach
We use a version of the density functional theory to study the changes in the
height of the tethered layer of chains built of jointed spherical segments with
the change of the length and surface density of chains. For the model in which
the interactions between segments and solvent molecules are the same as between
solvent molecules we have discovered two effects that have not been observed in
previous studies. Under certain conditions and for low surface concentrations
of the chains, the height of the pinned layer may attain a minimum. Moreover,
for some systems we observe that when the temperature increases, the height of
the layer of chains may decrease.Comment: 13 pages, 7 figure
Isobaric-isothermal molecular dynamics computer simulations of the properties of water-1,2-dimethoxyethane model mixtures
Isothermal-isobaric molecular dynamics simulations have been performed to
examine a broad set of properties of the model water-1,2-dimethoxyethane (DME)
mixture as a function of composition. The SPC-E and TIP4P-Ew water models and
the modified TraPPE model for DME were applied. Our principal focus was to
explore the trends of behaviour of the structural properties in terms of the
radial distribution functions, coordination numbers and number of hydrogen
bonds between molecules of different species, and of conformations of DME
molecules. Thermodynamic properties, such as density, molar volume, enthalpy of
mixing and heat capacity at constant pressure have been examined. Finally, the
self-diffusion coefficients of species and the dielectric constant of the
system were calculated and analyzed.Comment: 14 pages, 9 figure
Emiss T in first ATLAS data
In December 2009 ATLAS collected more than half a million of minimum bias events at center-of-mass energy of 900GeV and 2.36TeV. These events offer a good opportunity to test the performance of missing-transverse-energy (Emiss T)
reconstruction with up to 100 GeV total transverse energy per event. Resolution and tails of missing-transverse-energy distribution are in good agreement with the
simulation. In this early stage, only calorimeter-based missing transverse energy is considered and all cell energies are calibrated at the electromagnetic (EM) scale
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.Comment: 16 pages, 18 figure
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.Comment: 15 pages, 14 figure
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