scholarly journals Molecular dynamic simulation study of molten cesium

2017 ◽  
Vol 82 (6) ◽  
pp. 681-694 ◽  
Author(s):  
Saeid Yeganegi ◽  
Vahid Moeini ◽  
Zohreh Doroodi
Keyword(s):  
Internal Pressure ◽  
Diffusion Coefficients ◽  
Distribution Functions ◽  
Radial Distribution Functions ◽  
Coordination Numbers ◽  
Self Diffusion ◽  
Temperature And Pressure ◽  
Molecular Dynamic Simulation Study ◽  
Dynamics Simulations ◽  
And Diffusion

Molecular dynamics simulations were performed to study thermodynamics and structural properties of expanded caesium fluid. Internal pressure, radial distribution functions (RDFs), coordination numbers and diffusion coefficients have been calculated at temperature range 700?1600 K and pressure range 100?800 bar. We used the internal pressure to predict the metal?non-metal transition occurrence region. RDFs were calculated at wide ranges of temperature and pressure. The coordination numbers decrease and positions of the first peak of RDFs slightly increase as the temperature increases and pressure decreases. The calculated self-diffusion coefficients at various temperatures and pressures show no distinct boundary between Cs metallic fluid and its expanded fluid where it continuously increases with temperature.

A MOLECULAR DYNAMICS STUDY OF OXYGEN GAS IN WATER AT DIFFERENT TEMPERATURES

2013 ◽  
Vol 27 (08) ◽  
pp. 1350023 ◽  
Author(s):  
S. K. THAPA ◽  
N. P. ADHIKARI
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficients ◽  
Distribution Functions ◽  
Self Diffusion ◽  
Water As Solvent ◽  
Different Temperatures ◽  
Oxygen Gas ◽  
Dynamics Simulations ◽  
Solvent Solvent

Molecular dynamics simulations of a binary mixture of oxygen gas and SPC/E water, with oxygen gas ( O 2) as solute and water as solvent, at oxygen mole fraction of 0.019 have been accomplished at different temperatures 288, 293, 298, 302 and 306 K using Groningen Machine for Chemical Simulations. The solvent–solvent, solute–solute and solute–solvent radial distribution functions (RDFs) have been estimated. The solvent–solvent (water–water) RDF has been found to agree with that obtained from NMR/X-ray data within 7%. Self-diffusion coefficients of both the solvent and the solute have been determined by means of mean-squared displacement curves using Einstein's relation. They are found to agree with experimental results very well. Darken's relation has also been invoked for the determination of mutual diffusion coefficients at the respective temperatures. The analysis of temperature dependence of the diffusion coefficients has revealed that they follow Arrhenius equation to a very good extent and are consistent with the nature of RDF's at the respective temperatures. The estimated activation energies are in excellent agreement with the available experimental data.

Molecular Dynamics Study of the Effect of Pressure on an Aqueous NaCl Solution

1985 ◽  
Vol 40 (12) ◽  
pp. 1235-1247 ◽  
Author(s):  
G. Jancsó ◽  
K. Heinzinger ◽  
P. Bopp
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficients ◽  
Room Temperature ◽  
Bulk Water ◽  
Force Model ◽  
Nacl Solution ◽  
Self Diffusion ◽  
Dynamical Properties ◽  
Temperature And Pressure ◽  
Dynamics Simulations

Molecular dynamics simulations of a 2.2 molal NaCI solution at room temperature and pressure of 1 bar and 10 kbar have been performed employing a modified version of the central-force model of water. The changes in the structural and dynamical properties of the solution resulting from the increase in pressure are reported. The effect of ions on the self-diffusion coefficients of hydration and bulk water and on the IR spectroscopical properties of the solution is also discussed and compared with the available experimental data.

scholarly journals Self-Diffusion Coefficients of Methane/n-Hexane Mixtures at High Pressures: An Evaluation of the Finite-Size Effect and a Comparison of Force Fields

2019 ◽  
Author(s):  
Thiago José Pinheiro dos Santos ◽  
Charlles Abreu ◽  
Bruno Horta ◽  
Frederico W. Tavares
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficients ◽  
High Pressures ◽  
Force Fields ◽  
Transport Coefficients ◽  
Finite Size ◽  
Finite Size Effect ◽  
Self Diffusion ◽  
Analytical Correction ◽  
Dynamics Simulations

Mass transport coefficients play an important role in process design and in compositional grading of oil reservoirs. As experimental measurements of these properties can be costly and hazardous, Molecular Dynamics simulations emerge as an alternative approach. In this work, we used Molecular Dynamics to calculate the self-diffusion coefficients of methane/n-hexane mixtures at different conditions, in both liquid and supercritical phases. We evaluated how the finite box size and the choice of the force field affect the calculated properties at high pressures. Results show a strong dependency between self-diffusion and the simulation box size. The Yeh-Hummer analytical correction [J. Phys. Chem. B, 108, 15873 (2004)] can attenuate this effect, but sometimes makes the results depart from experimental data due to issues concerning the force fields. We have also found that different all-atom and united-atom models can produce biased results due to caging effects and to different dihedral configurations of the n-alkane.

Study by Numerical Simulation of the Structural and Dynamical Properties of the Fused LiCl-KCl Eutectic

1984 ◽  
Vol 39 (2) ◽  
pp. 162-168 ◽  
Author(s):  
F. Lantelme ◽  
P. Turq
Keyword(s):  
Diffusion Coefficients ◽  
Large Range ◽  
Memory Function ◽  
Distribution Functions ◽  
Coulomb Energy ◽  
Radial Distribution Functions ◽  
Volume Changes ◽  
Lithium Ions ◽  
Ionic Motion ◽  
Binary Collisions

The ionic properties of the eutectic LiCl-KCl melt are examined in a large range of temperature and density. The radial distribution functions are calculated. It is shown that, although the contribution of the Coulomb energy to the thermodynamic properties decreases at high temperatures it remains always predominant and explains the temperature dependence of the specific heat at constant volume. The diffusion coefficients of Li+, K+ and Cl- are determined. The mechanism of the ionic motion is studied through the memory function formalism. Two types of motion are detected, which arise from binary collisions and from dynamical events which involve a large number of ions. Temperature and volume changes show that the lithium ions remain always surrounded by a more structured atmosphere which hinders their motion. This effect becomes more apparent at high temperature and low density.

scholarly journals Molecular Simulation of the Adsorption and Diffusion in Cylindrical Nanopores: Effect of Shape and Fluid–Solid Interactions

Molecules ◽  
2019 ◽  
Vol 24 (3) ◽  
pp. 608 ◽  
Author(s):  
Harry Cárdenas ◽  
Erich Müller
Keyword(s):  
Decisive Role ◽  
Molecular Shape ◽  
Type I ◽  
Surface Strength ◽  
Bulk Fluid ◽  
Self Diffusion ◽  
Interaction Sites ◽  
Adsorbed Phase ◽  
Dynamics Simulations ◽  
And Diffusion

We report on molecular simulations of model fluids composed of three tangentially bonded Lennard-Jones interaction sites with three distinct morphologies: a flexible “pearl-necklace” chain, a rigid “stiff” linear configuration, and an equilateral rigid triangular ring. The adsorption of these three models in cylindrical pores of diameters 1, 2, and 3 nm and with varying solid–fluid strength was determined by direct molecular dynamics simulations, where a sample pore was placed in contact with a bulk fluid. Adsorption isotherms of Type I, V, and H1 were obtained depending on the choice of pore size and solid–fluid strength. Additionally, the bulk-phase equilibria, the nematic order parameter of the adsorbed phase, and the self-diffusion coefficient in the direction of the pore axis were examined. It was found that both the molecular shape and the surface attractions play a decisive role in the shape of the adsorption isotherm. In general, the ring molecules showed a larger adsorption, while the fully flexible model showed the smallest adsorption. Morphology and surface strength were found to have a lesser effect on the diffusion of the molecules. An exceptional high adsorption and diffusion, suggesting an enhanced permeability, was observed for the linear stiff molecules in ultraconfinement, which was ascribed to a phase transition of the adsorbed fluid into a nematic liquid crystal.

Molecular-Dynamics Analysis of the Structural Properties of Silica during Cooling

2008 ◽  
Vol 139 ◽  
pp. 101-106 ◽  
Author(s):  
Byoung Min Lee ◽  
Shinji Munetoh ◽  
Teruaki Motooka ◽  
Yeo Wan Yun ◽  
Kyu Mann Lee
Keyword(s):  
Molecular Dynamics ◽  
Glass Transition ◽  
Transition Temperature ◽  
Structural Properties ◽  
Diffusion Coefficients ◽  
The Self ◽  
Dynamics Analysis ◽  
Self Diffusion ◽  
Dynamics Simulations ◽  
Potential Parameters

The structural properties of SiO2 liquid during cooling have been investigated by molecular dynamics simulations. The interatomic forces acting on the particles are calculated by the modified Tersoff potential parameters. The glass transition temperature and structural properties of the resulting SiO2 system at various temperatures have been investigated. The fivefold coordinations of Si and threefold coordinations of O atoms were observed, and the coordination defects of system decrease with decreasing temperature up to 17 % at 300 K. The self-diffusion coefficients for Si and O atoms drop to almost zero below 3000 K. The structures were distorted at high temperatures, but very stable atomic network persisted up to high temperature in the liquid state.

The structural transition under compression and correlation between structural and dynamical heterogeneity for liquid Al2O3

2019 ◽  
Vol 33 (31) ◽  
pp. 1950380
Author(s):  
P. H. Kien ◽  
P. M. An ◽  
G. T. T. Trang ◽  
P. K. Hung
Keyword(s):  
Structural Transition ◽  
3D Visualization ◽  
Structural Characteristics ◽  
Length Distribution ◽  
Distribution Functions ◽  
Radial Distribution Functions ◽  
Structural Units ◽  
Dynamical Heterogeneity ◽  
Self Diffusion ◽  
Bond Length Distribution

This study reported a simulation of structural transition and correlation between structural and dynamical heterogeneity (DH) for liquid Al2O3. Structural characteristics of liquid Al2O3 were clarified through the pair radial distribution functions, the distribution of [Formula: see text] and [Formula: see text] ([Formula: see text], 4, 5, 6; [Formula: see text], 2, 3) basic structural units, angle and bond length distribution and 3D visualization. Simulation results revealed that network structure of liquid Al2O3 is built mainly by AlO3, AlO4, AlO5 and AlO6 units that are linked to each other through common oxygen atoms. We found the existence of separate AlO4-, AlO5- and AlO6-phases where the mobility of atoms can be determined. The atoms in AlO4-phase are more mobile than the ones in AlO5- and AlO6-phases. The existence of separate phases is evidence of DH in liquid Al2O3. Moreover, the self-diffusion of Al and O atoms was also discussed via characteristics of separate AlO4-, AlO5- and AlO6-phases.

A Molecular Dynamics Simulation of Molten (Li-Rb)Cl Implying the Chemla Effect of Mobilities

1980 ◽  
Vol 35 (5) ◽  
pp. 493-499 ◽  
Author(s):  
Isao Okada ◽  
Ryuzo Takagi ◽  
Kazutaka Kawamura
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Diffusion Coefficients ◽  
Strong Correlation ◽  
Pair Correlation ◽  
The Self ◽  
Dynamics Simulation ◽  
Self Diffusion ◽  
Pure Salt ◽  
Dynamics Simulations

Abstract A new transport property, the self-exchange velocity (SEV) of neighbouring unlike ions, has been evaluated from molecular dynamics simulations of molten LiCl, RbCl and LiRbCl2 at 1100 K and the mixture at 750 K. From the increase of the SEV's in the order Rb+ (pure salt) <Li+ (mixture) < Rb+ (mixture) < Li+ (pure salt), it is conjectured that there is a strong correlation between the SEV’s and the internal mobilities. An interpretation of the Chemla effect in its dependence on temperature is given. The pair correlation functions and the self-diffusion coefficients are also calculated and discussed.

First Principles Molecular Simulations of Soda-Lime-Silica Glass

2008 ◽  
Vol 39-40 ◽  
pp. 85-88 ◽  
Author(s):  
Jan Macháček ◽  
Soňa Charvátová ◽  
Ondrej Gedeon ◽  
Marek Liška
Keyword(s):  
First Principles ◽  
Md Simulation ◽  
Soda Lime ◽  
Md Simulations ◽  
Distribution Functions ◽  
Basis Set ◽  
Ab Initio Molecular Dynamics ◽  
Radial Distribution Functions ◽  
Coordination Numbers ◽  
Soda Lime Silica Glass

This work aims to explore possible applications of the ab initio molecular dynamics (MD) in modeling of the soda-lime-silica (NCS) glass and melt doped with admixtures. Preparation of the basic glass (15.8 wt.% Na2O, 10.5 wt.% CaO, and 73.7 wt.% SiO2) by the MD simulation from scratch is described. The structure analysis of the NCS glass is presented in the form of total and partial radial distribution functions (RDF), coordination numbers, and fractions of Qn units. The reasonable first neighbor distances were obtained, even if a rather small basis set of electronic wavefunctions and softer pseudopotentials for atomic core regions were applied. All major discrepancies in the first neighbor distances can be easily explained, and the results can be improved if needed. The Qn distribution shows higher disproportionation of Q3 than NMR and Raman experimental data, however, it is lower than previous classical MD simulations.

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