Structural properties of liquid aluminosilicate with varying Al2O3/SiO2 ratios: Insight from analysis and visualization of molecular dynamics data

2017 ◽  
Vol 31 (05) ◽  
pp. 1750036 ◽  
Author(s):  
N. V. Yen ◽  
M. T. Lan ◽  
L. T. Vinh ◽  
N. V. Hong
Keyword(s):  
Molecular Dynamics ◽  
Random Network ◽  
Md Simulations ◽  
Degree Of Polymerization ◽  
Distribution Functions ◽  
Molar Ratio ◽  
Nonbridging Oxygen ◽  
Structural Units ◽  
Self Diffusion ◽  
Continuous Random Network

Molecular dynamics (MD) simulations and visualizations were explored to investigate the changes in structure of liquid aluminosilicates. The models were constructed for four compositions with varying Al2O3/SiO2 ratio. The local structure and network topology was analyzed through the pair of radial distribution functions, bond angle, bond length and coordination number distributions. The results showed that the structure of aluminosilicates mainly consists of the basic structural units TO[Formula: see text] (T is Al or Si; y = 3, 4, 5). Two adjacent units TO[Formula: see text] are linked to each other through common oxygen atoms and form continuous random network of basic structural units TO[Formula: see text]. The bond statistics (corner-, edge- and face- sharing) between two adjacent TO[Formula: see text] units are investigated in detail. The self-diffusion coefficients for three atomic types are affected by the degree of polymerization (DOP) of network characterized by the proportions of nonbridging oxygen (NBO) and Q[Formula: see text] species in the system. It was found that Q4 and Q3 tetrahedral species (tetrahedron with four and three bridging oxygens, respectively) decreases, while Q0 (with four nonbridging oxygen) increase with increasing Al2O3/SiO2 molar ratio, suggesting that a less polymerized network was formed. The structural and dynamical heterogeneities, micro-phase separation and liquid–liquid phase transition are also discussed in this work.

Structural and Mechanical Properties of Nanophase Ni: A Molecular-Dynamics Study of the Influence of Grain-Boundary Structure on Elastic and Plastic Behavior

1997 ◽  
Vol 492 ◽  
Author(s):  
H. Van Swygenhoven ◽  
M. Spaczér ◽  
A. Caro
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Diffusion Mechanism ◽  
Distribution Functions ◽  
Boundary Structure ◽  
Plastic Behavior ◽  
Self Diffusion ◽  
Common Neighbour ◽  
Grain Boundary Structure

ABSTRACTMolecular dynamics computer simulations of high load plastic deformation at temperatures up to 500K of Ni nanophase samples with mean grain size of 5 nm are reported. Two types of samples are considered: a polycrystal nucleated from different seeds, each having random location and random orientation, representing a sample with mainly high angle grain boundaries, and polycrystals with seeds located at the same places as before, but with a limited missorientation representing samples with mainly low angle grain boundaries. The structure of the grain boundaries is studied by means of pair distribution functions, coordination number, atom energetics, and common neighbour analysis. Plastic behaviour is interpreted in terms of grain-boundary viscosity, controlled by a self diffusion mechanism at the disordered interface activated by thermal energy and stress.

scholarly journals Investigation of Microscopic Structure and Ion Dynamics in Liquid Li(Na, K)EutecticCl Systems by Molecular Dynamics Simulation

2018 ◽  
Vol 8 (10) ◽  
pp. 1874 ◽  
Author(s):  
Jie Wu ◽  
Jia Wang ◽  
Haiou Ni ◽  
Guimin Lu ◽  
Jianguo Yu
Keyword(s):  
Molecular Dynamics ◽  
Ionic Conductivity ◽  
Shear Viscosity ◽  
Ion Pairs ◽  
Liquid Structure ◽  
Distribution Functions ◽  
Dynamics Simulation ◽  
Molten Chloride ◽  
Ion Clusters ◽  
Self Diffusion

Molten chloride salts are the main components in liquid metal batteries, high-temperature heat storage materials, heat transfer mediums, and metal electrolytes. In this paper, interest is centered on the influence of the LiCl component and temperature on the local structure and transport properties of the molten LiCl-NaCl-KCl system over the temperature range of 900 K to 1200 K. The liquid structure and properties have been studied across the full composition range by molecular dynamics (MD) simulation of a sufficient length to collect reliable values, such as the partial radial distribution function, angular distribution functions, coordination numbers distribution, density, self-diffusion coefficient, ionic conductivity, and shear viscosity. Densities obtained from simulations were underestimated by an average 5.7% of the experimental values. Shear viscosities and ionic conductivity were in good agreement with the experimental data. The association of all ion pairs (except for Li-Li and Cl-Cl) was weakened by an increasing LiCl concentration. Ion clusters were formed in liquids with increasing temperatures. The self-diffusion coefficients and ionic conductivity showed positive dependences on both LiCl concentration and temperature, however, the shear viscosity was the opposite. By analyzing the hydrodynamic radii of each ion and the coordination stability of cation-anion pairs, it was speculated that ion clusters could be the cation-anion coordinated structure and affected the macro properties.

Fluctuation Microscopy in the STEM

2001 ◽  
Vol 7 (S2) ◽  
pp. 226-227
Author(s):  
P. M. Voyles ◽  
D. A. Muller
Keyword(s):  
Random Network ◽  
Dark Field ◽  
Distribution Functions ◽  
Disordered Materials ◽  
Microscopy Technique ◽  
Medium Range ◽  
Fluctuation Microscopy ◽  
Image Position ◽  
Continuous Random Network ◽  
Vector Magnitude

Fluctuation microscopy is an electron microscopy technique sensitive to medium-range order (MRO) in disordered materials. It has been applied to study amorphous germanium and silicon, leading to the conclusion that these materials exhibit more MRO than the conventional continuous random network model for their structure.As originally proposed by Treacy and Gibson, fluctuation microscopy utilizes mesoscopicresolution (1.5 nm) hollow-cone dark field (HCDF) imaging in a TEM. The normalized variance of such images,is a measure of the magnitude of fluctuations in the diffracted intensity from mesoscopic volumes of the sample and is sensitive to MRO via the three- and four-body atom distribution functions. Studying V as a function of the diffraction vector magnitude k gives information about the degree of MRO and the internal structure of ordered regions. V as a function of the inverse resolution Q gives information about the characteristic MRO length scale.

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.

Molecular Dynamics Simulation to Study the Effect of Empirical Potential Functions on Modeling of Diamond-Like Carbon

2013 ◽  
Author(s):  
Longqiu Li ◽  
Ming Xu ◽  
Wenping Song ◽  
Guangyu Zhang ◽  
Andrey Ovcharenko
Keyword(s):  
Molecular Dynamics ◽  
Amorphous Carbon ◽  
Md Simulations ◽  
Distribution Functions ◽  
Dynamics Simulation ◽  
Empirical Potential ◽  
Mechanical And Tribological Properties ◽  
Empirical Potentials ◽  
Rebo Potential ◽  
Quenching Method

Molecular dynamics (MD) simulations is an effective method to investigate the mechanical and tribological properties of amorphous carbon since the coordinates of all atoms can be calculated as a function of time. Several empirical potentials can be used to model the interatomic interactions of carbon atoms, including the Tersoff potential, the Reactive Bond Order (REBO) potential and its revised versions, and the Reactive Force Field (ReaxFF) potential. The choice of empirical potential is one of the fundamental and important assumptions in the MD approach since it can affect the properties of amorphous carbon during the MD simulations. In this study, liquid quenching method is used to model amorphous carbon for computational efficiency. We will study the influence of the three types of potentials, specifically the Tersoff potential, the 2nd REBO potential and the ReaxFF potential on DLC parameters. These parameters include the sp3 content as a function of density, the arrangement of the amorphous carbon atoms, hybridization and the radial distribution functions G(r).

New View of Low-Temperature Sintering Phenomenon of Nanometer-Size Particles Based on Molecular Dynamics Study

MRS Advances ◽  
2016 ◽  
Vol 1 (30) ◽  
pp. 2167-2172
Author(s):  
Norie Matsubara ◽  
Shinji Munetoh ◽  
Osamu Furukimi
Keyword(s):  
Molecular Dynamics ◽  
Surface Layer ◽  
Diffusion Coefficient ◽  
Heating Temperature ◽  
Md Simulations ◽  
Atomic Scale ◽  
Self Diffusion ◽  
The Mean ◽  
The Relationship ◽  
Self Diffusion Coefficient

ABSTRACTIn this study, we have investigated a behavior of particle with diameter several ten nanometers size at the time of heating on an atomic scale by numerical analysis using the molecular dynamics (MD) simulation. On solving the equation of motion, the Langevin equation was adopted. The Finnis-Sinclair potential, which can well reproduce the mechanical properties of a BCC-metal, was used as the interatomic force. We determined the relationship between the melting point (Tm) of the nano-sized particles and its diameter by MD simulations. We have also investigated the self-diffusion coefficient of each atom-forming at a temperature larger or less than Tm of the submicron-size metal particles . As a result, even in case of heating at a temperature larger than Tm, the mean self-diffusion coefficient at the center of a particle was 10-7–10-6 cm2/sec. On the other hand, at the surface layer of the particle was two to three orders of magnitude larger than that at the center. Those particles were in a quasi-molten state. It is conceivable that the thickness of the surface layer can explain a phenomenon that sintering progresses as the heating temperature increases.

Molecular Dynamics Simulation of Molten Alkali Nitrates

2001 ◽  
Vol 56 (5) ◽  
pp. 337-341 ◽  
Author(s):  
G. Vöhringer ◽  
J. Richter
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficients ◽  
Short Range ◽  
Spin Echo ◽  
Isotope Effects ◽  
Pair Potential ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Self Diffusion ◽  
Transport Effects

Abstract Molecular dynamics (MD) simulations have been performed for several pure alkali nitrate melts. Special attention was paid to the examination of the interaction potential: macroscopic quantities like pressure were calculated and compared with real values. To improve the results the commonly used potential for alkali nitrates (Coulomb pair potential and Born-type repulsion) has been extended by a short-range-attraction term to meet the real behaviour of the liquid. With these improved potentials, simulations of pure LiNO3, NaNO3, KNO3, and RbNO3 have been performed with special regard to the influence of size and mass of the cations on the transport effects to show analogies to isotope effects. The calculated self diffusion coefficients (SDC) have been compared to results obtained with the NMR spin echo method.

Structure and Dynamics of NaCl in Methanol. A Molecular Dynamics Study

1991 ◽  
Vol 46 (10) ◽  
pp. 887-897 ◽  
Author(s):  
D. Marx ◽  
K. Heinzinger ◽  
G. Pálinkás ◽  
I. Bakó
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficients ◽  
Distribution Functions ◽  
Dynamics Simulation ◽  
Nacl Solution ◽  
Geometrical Arrangement ◽  
Self Diffusion ◽  
Site Model ◽  
Structure And Dynamics ◽  
Dynamical Properties

AbstractA recently developed flexible three-site model for methanol was employed to perform a Molecular Dynamics simulation of a 0.6 molal NaCl solution. The ion-methanol and ion-ion potential functions were derived from ab initio calculations. The structural properties of the solution are discussed on the basis of radial and angular distribution functions, the orientation of the methanol molecules, and their geometrical arrangement in the solvation shells of the ions. The dynamical properties of the solution - like self-diffusion coefficients, hindered translations, librations, and internal vibrations of the methanol molecules - are calculated from various autocorrelation functions.

Molecular dynamics simulation of interhalogen compounds. 1. Liquid chlorine trifluoride (ClF3): structure and thermodynamics

1992 ◽  
Vol 70 (1) ◽  
pp. 34-38 ◽  
Author(s):  
Ramesh K. Wadi ◽  
Vivek Saxena
Keyword(s):  
Molecular Dynamics ◽  
Thermodynamic Properties ◽  
Md Simulation ◽  
Pair Potential ◽  
Liquid Structure ◽  
Spectroscopic Studies ◽  
Distribution Functions ◽  
Dynamics Simulation ◽  
Self Diffusion ◽  
Laser Raman

The results of a molecular dynamics (MD) simulation study of liquid chlorine trifluoride (ClF3) at 217, 260, and 287 K are reported. The cubic simulation cell consists of 108 ClF3 molecules assumed to be interacting via site–site Lennard–Jones 12–6 pair potential. The parameters for F–F and Cl–Cl interaction are the same as used for the simulation of F2, and Cl2, respectively, and those for the Cl–F cross interaction are calculated using Lorentz–Berthelot rules. These results are then used to calculate various radial distribution functions characteristic of the liquid structure. Thermodynamic properties, namely, configurational energy, constant volume specific heat, and internal pressure are also reported. The time-dependent properties, mean square force and torque, self diffusion coefficient, and the quantum corrections to the free energy, were also obtained. The dimer configuration drawn based on the observed contact distances was found to be in good agreement with the results of matrix isolation infrared and laser Raman spectroscopic studies. Keywords: MD simulation, interhalogens, liquid structure, thermodynamic properties.

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.

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