Estimation of the Self and Mutual Diffusion Coefficients in Molten CdTe by a Molecular Dynamics Technique

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.

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Molecular Dynamics Simulation of Diffusion Behavior of CH4, CO2, and N2 in Mid-Rank Coal Vitrinite

Energies ◽

10.3390/en12193744 ◽

2019 ◽

Vol 12 (19) ◽

pp. 3744

Author(s):

Jing Liu ◽

Shike Li ◽

Yang Wang

Keyword(s):

Molecular Dynamics ◽

Diffusion Coefficients ◽

Coalbed Methane ◽

Peak Pressure ◽

The Self ◽

Dynamics Simulation ◽

Diffusion Activation Energy ◽

Gas Concentration ◽

Diffusion Characteristics ◽

Diffusion Activation

The diffusion characteristics of CH4, CO2, and N2 in coal are important for the study of CO2-enhanced coalbed methane (CO2-ECBM) recovery, which has become the most potential method for carbon sequestration and natural gas recovery. However, quantitative research on the diffusion characteristics of CH4 and the invasive gases (CO2 and N2) in coal, especially those in micropores, still faces enormous challenges. In this paper, the self-, Maxwell’s, and transport diffusions of CO2, CH4, and N2 in mid-rank coal vitrinite (MRCV) macromolecules were simulated based on the molecular dynamics method. The effects of the gas concentration, temperature, and pressure on the diffusion coefficients were examined via the comparison of various ranks. The results indicated that the diffusion coefficients have the order of D(N2) > D(CO2) > D(CH4) in their saturated adsorption states. However, when MRCV adsorbed the same amounts of CH4, CO2, and N2, the self- and transport diffusion coefficients followed the order of DS(N2) > DS(CO2) > DS(CH4) and Dt(CO2) > Dt(N2) > Dt(CH4), respectively. Independent of the gas species, all these diffusion coefficients decreased with increasing gas concentration and increased with increasing temperature. In the saturated adsorption state, the diffusion activation energies of CH4, CO2, and N2 were ordered as CH4 (27.388 kJ/mol) > CO2 (11.832 kJ/mol) > N2 (10.396 kJ/mol), indicating that the diffusion processes of CO2 and N2 occur more easily than CH4. The increase of temperature was more conducive to the swelling equilibrium of coal. For the pressure dependence, the diffusion coefficients first increased until the peak pressure (3 MPa) and then decreased with increasing pressure. In contrast, the diffusion activation energy first decreased and then increased with increasing pressure, in which the peak pressure was also 3 MPa. The swelling rate changed more obviously in high-pressure conditions.

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

Zeitschrift für Naturforschung A ◽

10.1515/zna-1980-0505 ◽

1980 ◽

Vol 35 (5) ◽

pp. 493-499 ◽

Cited By ~ 8

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.

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Molecular dynamics simulation of self- and mutual diffusion coefficients for confined mixtures

The Journal of Chemical Physics ◽

10.1063/1.2050627 ◽

2005 ◽

Vol 123 (14) ◽

pp. 144701 ◽

Cited By ~ 9

Author(s):

Li Zhang ◽

Ying-Chun Liu ◽

Qi Wang

Keyword(s):

Molecular Dynamics ◽

Molecular Dynamics Simulation ◽

Diffusion Coefficients ◽

Mutual Diffusion ◽

Dynamics Simulation

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Molecular-Dynamics Simulation of Self-Diffusion of Molecular Hydrogen in X-Type Zeolite

Journal of Chemistry ◽

10.1155/2013/545367 ◽

2013 ◽

Vol 2013 ◽

pp. 1-7 ◽

Cited By ~ 1

Author(s):

Xiaoming Du

Keyword(s):

Molecular Dynamics ◽

Diffusion Coefficients ◽

Hydrogen Diffusion ◽

Mean Free Path ◽

The Self ◽

Dynamics Simulation ◽

Pulse Field ◽

Self Diffusion ◽

Hydrogen Molecules ◽

Dynamics Simulations

The self-diffusion of hydrogen in NaX zeolite has been studied by molecular-dynamics simulations for various temperatures and pressures. The results indicate that in the temperature range of 77–293 K and the pressure range of 10–2700 kPa, the self-diffusion coefficients are found to range from 1.61 × 10−9 m2·s−1to 3.66 × 10−8 m2·s−1which are in good agreement with the experimental values from the quasielastic neutron scattering (QENS) and pulse field gradients nuclear magnetic resonance (PFG NMR) measurements. The self-diffusion coefficients decrease with increasing pressure due to packing of sorbate-sorbate molecules which causes frequent collusion among hydrogen molecules in pores and increase with increasing temperature because increasing the kinetic energy of the gas molecules enlarges the mean free path of gas molecule. The activated energy for hydrogen diffusion determined from the simulation is pressure-dependent.

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