Mobility of Ag Atoms in the Binary System Ag2Se-Ag2S: A Molecular Dynamics Study

1997 ◽  
Vol 481 ◽  
Author(s):  
A. Smith ◽  
R. Ravelo ◽  
N. Pingitore
Keyword(s):  
Phase Transition ◽  
Activation Energy ◽  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Binary System ◽  
Arrhenius Plot ◽  
Diffusion Mechanism ◽  
Experimental Measurements ◽  
End Points ◽  
Activation Energy For Diffusion

ABSTRACTThe compounds in the binary system Ag2Se-Ag2S are known to undergo a phase transition to a superionic phase at a temperature which varies with concentration. The diffusion mechanism of Ag ions have been studied in a Molecular Dynamics formalism. We have calculated the diffusion coefficient as function of temperature and concentration and have calculated the activation energy for diffusion from the Arrhenius plot of DAg vs temperature. Results obtained for the end points Ag2Se and Ag2S agree with experimental measurements.

Molecular Dynamics Simulation Study of the Effect of Ni, Fe, Cu on Cryolite Molten Salt System 78% Na3AlF6-9.5%AlF3-5.0%CaF2-7.5%-Al2O3

2021 ◽  
Vol 1026 ◽  
pp. 39-48
Author(s):  
Han Bing He ◽  
Yu Si Wang ◽  
Ze Xiang Luo ◽  
Jing Zeng
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Molten Salt ◽  
Diffusion Mechanism ◽  
Research Work ◽  
Dynamics Simulation ◽  
Salt System ◽  
Electrolyte System ◽  
Aluminum Composite ◽  
Molten Salt System

The effect of different additives Ni, Fe, Cu on the structure and properties of electrolyte system 78% Na3AlF6- -9.5%AlF3-5.0%CaF2-7.5%Al2O3 at 1200K and 1.01Mpa was studied by molecular dynamics method. The radial distribution function, coordination number, diffusion coefficient, conductivity, and viscosity of the system were discussed in detail. The results demonstrated that the order of the self-diffusion coefficient of ions in the electrolyte system is: Na+ > F- > O2- > Ca2+ >Al3+. The addition of Ni and Fe connected the free aluminum composite ion groups in the system through fluorine bridges, which enhanced the interaction between Al3+ and Al3+. The addition of Cu weakened the interaction between Al3 + and Al3+ and the F-. The interaction between Al3+ and Na+, [AlF7]4- ionic groups might appeared in the melt system. After adding NiO, Fe2O3, and Cu, the electrical conductivity of the system increased, and the viscosity decreased. The research work revealed the influence of Ni, Fe, Cu on the ion existence form, mobility, inter-ion interaction and diffusion mechanism of cryolite molten salt system, which has important guiding significance for aluminum electrolysis production.

Tracer Impurity Diffusion in Liquid Metals: Au in Ga

1974 ◽  
Vol 29 (6) ◽  
pp. 959-960 ◽  
Author(s):  
P.-E. Eriksson ◽  
S. J. Larsson
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Low Temperatures ◽  
Arrhenius Plot ◽  
Liquid Metals ◽  
Impurity Diffusion ◽  
Straight Line ◽  
Linear Plot

The diffusion coefficient of 198Au in liquid Ga has been measured between 35 and 460 °C. The results can be represented by a linear plot of D vs T or by an Arrhenius plot. The latter yields the parameters D0 = 4.9·10-4 cm2/s and Q = 2.65 kcal/mol. However, some distinct departures from the straight line characteristics, showing a considerably higher “activation energy” at the low temperatures, suggest the possibility that clusters composed of two or several atoms may partake in diffusion.

Diffusion Mechanisms in Bcc-Zr:A Molecular Dynamics Approach

1990 ◽  
Vol 209 ◽  
Author(s):  
F. Willaime ◽  
C. Massobrio
Keyword(s):  
Activation Energy ◽  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Interatomic Potential ◽  
Migration Energy ◽  
Vacancy Migration ◽  
Migration Mechanism ◽  
Diffusion Mechanisms ◽  
Dynamics Simulations ◽  
Bcc Phase

ABSTRACTBasing our calculations on a realistic N-body interatomic potential for Zr, we study the vacancy migration mechanism and determine the related diffusion coefficient in the bcc phase. The form of the potential energy along the nearest-neighborjump migration path is single-peaked. The vacancy jump rate determined by molecular dynamics simulations has a perfectly Arrhenian behavior and its activation energy is very close to the static value of the vacancy migration energy, both being very low (≈ 0.3 eV) . The diffusion coefficient is in very satisfactory agreement with experiments.

Surface Diffusion of Sulfur on Nickel (110) and the Effect of Carbon on the Diffusivity

1992 ◽  
Vol 280 ◽  
Author(s):  
Barbara Ladna ◽  
Howard K. Birnbaum
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Surface Diffusion ◽  
Half Plane ◽  
Auger Electron ◽  
Arrhenius Plot ◽  
Electron Spectrometer ◽  
Plane Source ◽  
Surface Diffusion Coefficient ◽  
Diffusion Profiles

ABSTRACTThe surface diffusion coefficient of sulfur on the (110) surface of nickel was determined at temperatures of 623, 673 and 723 K by measurement of surface diffusion profiles using an Auger Electron Spectrometer. A half-plane monolayer of segregated sulfur was used as a source and the analysis was done by a Boltzmann-Matano method. The activation energy for surface diffusion of sulfur was determined to be about 106 kJ/mol and pre-exponential Do to be about 6×10-3 m2/s from the Arrhenius plot of D versus 1/T. The presence of carbon on the surface of nickel was shown to decrease the surface diffusion of sulfur. Also, the mechanism of spreading from the half-plane source changed from a classic surface diffusion on clean surfaces to a linear mobility of the sulfur-carbon interface on surfaces covered with carbon.

Hydrogen Diffusion in Quartz: A Molecular Dynamics Investigation

1995 ◽  
Vol 408 ◽  
Author(s):  
A. Bongiorno ◽  
L. Colombo
Keyword(s):  
Activation Energy ◽  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Hydrogen Diffusion ◽  
Diffusion Path ◽  
Arrhenius Law ◽  
Hydrogen Diffusivity ◽  
Temperature Dependent ◽  
Crystalline Quartz ◽  
Wide Range

AbstractWe present a molecular dynamics investigation on hydrogen diffusivity in crystalline quartz by computing the diffusion coefficient over a wide range of temperatures (700K < T < 1500K) and by characterizing the diffusion path and mechanism. Our main findings are: (i) hydrogen diffusion is anisotropically confined along the c-axis in α- and β-quartz; (ii) hydrogen diffuses through a jump-like mechanism; (iii) the temperature-dependent diffusivity follows an Arrhenius law with activation energy of 0.56 eV and 0.27 eV for α-and β-quartz, respectively.

Iron Self-Diffusion in Chemically Homogeneous Multilayers

2005 ◽  
Vol 237-240 ◽  
pp. 548-553 ◽  
Author(s):  
Mukul Gupta ◽  
Ajay Gupta ◽  
Sujoy Chakravarty ◽  
Thomas Gutberlet
Keyword(s):  
Activation Energy ◽  
Compressive Stress ◽  
Applied Stress ◽  
Diffusion Mechanism ◽  
Neutron Reflectivity ◽  
Self Diffusion ◽  
Significant Dependence ◽  
Activation Energy For Diffusion ◽  
Bulk Alloys ◽  
Nm Range

Iron self-diffusion measurements in amorphous and nanocrystalline chemically homogenous multilayers (CHM) of FeZr/57FeZr, (with nm range periodicity) have been studied with neutron reflectivity technique. It has been found that both the activation energy for diffusion and the pre-factor were significantly smaller as compared with bulk alloys. Effect of compressive stress on self-diffusion reveals a significant dependence on the activation energy as a function of applied stress. On the basis of the obtained results the diffusion mechanism in amorphous and nanocrystalline CHM of FeZr/57FeZr is reviewed in this paper.

scholarly journals PENGARUH KONSENTRASI DAN SUHU LARUTAN GULA PADA PROSES DEHIDRASI OSMOTIK BUAH NAGA (Hylocereus sp.)

Pro Food ◽  
2019 ◽  
Vol 5 (1) ◽  
pp. 440
Author(s):  
Spetriani Spetriani
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Moisture Content ◽  
Osmotic Dehydration ◽  
Initial Moisture Content ◽  
Moisture Diffusivity ◽  
Solution Temperature ◽  
Dragon Fruit ◽  
Activation Energy For Diffusion ◽  
Osmotic Solution

ABSTRACTOsmotic dehydration is a water removing process that carried out on a object by immersing the object into an hyper-tonic (osmotic) solution. The process is commonly applied on pre-drying of fruit. The purpose of this research is to investigate the effect of concentration and temperature of osmotic solution on moisture content change, total dissolved solids change and to determine of water diffusion coefficient and solid diffusion coefficient during the process of osmotic dehydration of dragon fruit. Factorial design was used with 2 factors, each consisting of 3 levels with 3 replication. The treatment on this research are : solution consentration of 30 °Brix, 50 °Brix, and 70 °Brix and solution temperature of 30 °C, 40 °C, and 50 °C were applied to this research. The osmotic dehydration process lasts for 8 hours. Initial moisture content of dragon fruit used for the research between 511.17-665.97 (% db). Moisture and solid diffusivities were in the range of 2.810 x 10-8 m²/s - 7.003 x 10-8 m²/s and 0.973 x 10-8 m²/s until 4.734 x 10-8 m²/s. The activation energy for diffusion of water to the concentration of 30 °Brix, 50 °Brix, and 70 °Brix respectively is 9.963 kJ/mol, 3.249 kJ/mol, and 5.372 kJ/mol. While the activation energy for diffusion of solids is 24.946 kJ/mol, 8.908 kJ/mol, and 27.343 kJ/mol. Keywords: dragon fruit, moisture diffusivity, osmotic dehydration, solid diffusivity ABSTRAK Dehidrasi osmotik adalah suatu proses pengeluaran air yang dilakukan terhadap suatu bahan dengan cara merendam bahan tersebut ke dalam suatu larutan hipertonik. Proses ini pada umumnya diaplikasikan untuk pra-pengeringan buah-buahan. Tujuan penelitian ini adalah untuk mengkaji pengaruh perlakuan konsentrasi dan suhu terhadap perubahan kadar air, perubahan total padatan terlarut dan untuk menentukan nilai koefisien difusi air dan difusi padatan selama proses dehidrasi osmotik pada buah naga. Digunakan rancangan faktorial dengan 2 faktor yang masing-masing terdiri atas 3 taraf dengan 3 kali ulangan. Perlakuan yang digunakan pada penelitian ini adalah variasi konsentrasi larutan 30 °Brix, 50 °Brix, dan 70 °Brix dan suhu larutan 30 °C, 40 °C, dan 50 °C. Proses dehidrasi osmotik berlangsung selama 8 jam. Kadar air awal buah naga yang digunakan untuk penelitian berkisar antara 511,17-665,97 (%db). Nilai difusivitas air antara 2,810 x 10-8 m²/s – 7,003 x 10-8 m²/s dan difusivitas padatan antara 0,973 x 10-8 m²/s - 4,734 x 10-8 m²/s. Energi aktivasi untuk difusi air untuk konsentrasi 30 °Brix, 50 °Brix, dan 70 °Brix secara berurutan adalah 9,963 kJ/mol, 3,249 kJ/mol, dan 5,372 kJ/mol. Energi aktivasi untuk difusi padatan adalah 24,946 kJ/mol, 8,908 kJ/mol, dan 27,343 kJ/mol. Kata kunci: buah naga, dehidrasi osmotik, difusivitas air, difusivitas padatan

Zinc Diffusion Rates and Profiles in AlGaAs Alloys

1991 ◽  
Vol 240 ◽  
Author(s):  
F. T. J. Smith
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Zinc Concentration ◽  
Diffusion Rate ◽  
Strong Dependence ◽  
Concentration Profiles ◽  
Diffusion Front ◽  
Activation Energy For Diffusion ◽  
Zinc Diffusion ◽  
Diffusion Rates

ABSTRACTThe diffusion rate of Zn in AlxGa1−xAs alloys has been determined, for values of x up to 1.0, as a function of temperature. At 625°C the diffusion coefficient shows a strong dependence on x, reaching a maximum at about 65% Al. A similar rapid increase in diffusion coefficient with x is seen at 700°C. The zinc concentration profiles are similar for all values of x, showing a very abrupt diffusion front. The activation energy for diffusion decreases with increasing x.

scholarly journals Simulating diffusion in the conditions of vapor-liquid phase transition by the molecular dynamics method

2021 ◽  
Vol 2057 (1) ◽  
pp. 012114
Author(s):  
G V Kharlamov
Keyword(s):  
Phase Transition ◽  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Liquid Phase ◽  
Diffusion Coefficients ◽  
Universal Function ◽  
Liquid Phase Transition ◽  
Lennard Jones ◽  
Almost All ◽  
Vapor Liquid

Abstract The molecular dynamics calculations of diffusion coefficients in binary Lennard-Jones systems have been carried out. The parameters of Lennard-Jones potentials correspond to argon and krypton atoms. The universal dependence of the reduced diffusion coefficient of krypton atoms on density for the homogeneous systems of low and middle densities is found. The deviations of the diffusion coefficients from the universal function are observed for the systems in the vapor – liquid phase transition region. The simulations have shown that almost all krypton atoms have situated inside the liquid phase of argon. Special numerical experiments have shown that the nanodroplets of argon are formed as a result of homogeneous nucleation and then the krypton atoms are captured by these droplets. This phenomenon decreases the diffusion coefficient of krypton atoms greatly.

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