Calculation of diffusion coefficients of two-electron metals in inert gases and molecular hydrogen

1991 ◽  
Vol 60 (6) ◽  
pp. 702-707
Author(s):  
K. M. Aref'ev ◽  
N. B. Balashova ◽  
M. A. Guseva
Keyword(s):  
Diffusion Coefficients ◽  
Molecular Hydrogen ◽  
Inert Gases

Diffusion coefficients of fluorescent organic molecules in inert gases

2013 ◽  
Vol 103 (4) ◽  
pp. 041911 ◽  
Author(s):  
Cedric Rolin ◽  
Stephen R. Forrest
Keyword(s):  
Diffusion Coefficients ◽  
Organic Molecules ◽  
Inert Gases

Electron Loss by Helium Atoms Passing through Inert Gases and Molecular Hydrogen, Nitrogen, and Oxygen

1973 ◽  
Vol 7 (1) ◽  
pp. 109-112 ◽  
Author(s):  
A. N. Tripathi ◽  
K. C. Mathur ◽  
S. K. Joshi
Keyword(s):  
Molecular Hydrogen ◽  
Inert Gases ◽  
Electron Loss ◽  
Helium Atoms

Tuning the Torsion Mechanical Properties of Carbon Nanotube by Feeding H2 Molecules

2013 ◽  
Vol 479-480 ◽  
pp. 75-79 ◽  
Author(s):  
Bin Hao Chen ◽  
Yi Wu Chao ◽  
Cheng Chi Wang
Keyword(s):  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Carbon Nanotube ◽  
Diffusion Coefficients ◽  
Md Simulations ◽  
Inert Gases ◽  
Nanoporous Material ◽  
Rigid Lattice ◽  
Hydrogen Molecules ◽  
Simulation Results

Carbon nanotubes (CNTs) have been proposed as one of the most promising materials for nanoelectro-mechanical system due to high elastic modulus, high failure strength and excellent resilience [1,. Recent development of many-body interaction [3, made possible realistic molecular dynamics (MD) simulations of carbon-made systems. We carried out such studies for carbon nanotubes under generic modes of mechanical load: axial compression, bending, and torsion. A singular behavior of the nanotube energy at certain levels of strain corresponds to abrupt change in morphology. In this letter, we report the torsional instability analysis of single wall carbon nanotube filled with hydrogen via molecular dynamics simulations. The simulations are carried out at a temperature 77K which previous study obtained the hydrogen storage inside CNT at this condition [A. C. Dillo. Here we use atomistic simulations to study a flexible surface narrow carbon nanotube with tube diameters 10.8 Å. According to conventional physisorption principles, the gas-adsorption performance of a porous solid is maximized when the pores are no larger than a few molecular diameters [8]. Under these conditions, the potential fields produced at the wall overlap to produce a stronger interaction force than that observed in adsorption on a simple plane. However, the mechanisms responsible for the adsorption and transportation of hydrogen in nanoporous solids or nanopores are not easily observed using experimental methods. As a result, the use of computational methods such as molecular dynamics (MD) or Monte Carlo (MC) simulations have emerged as the method of choice for examining the nanofluidic properties of liquids and gases within nanoporous materials [9,1. Several groups have performed numerical simulations to study the adsorption of water in CNTs [11-1, while others have investigated the diffusion of pure hydrocarbon gases and their mixtures through various SWNTs with diameters ranging from 2 ~ 8 nm [17-19] or the self-and transport diffusion coefficients of inert gases, hydrogen, and methane in infinitely-long SWNTs [20-21]. In general, the results showed that the transport rates in nanotubes are orders of magnitude higher than those measured experimentally in zeolites or other microporous crystalline solids. In addition, it has been shown that the dynamic flow of helium and argon atoms through SWNTs is highly dependent on the temperature of the nanotube wall surface [22]. Specifically, it was shown that the flow rate of the helium and argon atoms, as quantified in terms of their self-diffusion coefficients, increased with an increasing temperature due to the greater thermal activation effect. Previous MD simulations of the nanofluidic properties of liquids and gases generally assumed the nanoporous material to have a rigid structure. However, if the nanoporous material is not in fact rigid, the simulation results may deviate from the true values by several orders of magnitude. Several researchers have investigated the conditions under which the assumption of a rigid lattice is, or is not, reasonable [23, 24]. In general, the results showed that while the use of a rigid lattice was permissible in modeling the nanofluidic properties of a gas or liquid in an unconfined condition, a flexible lattice assumption was required when simulating the properties of a fluid within a constrained channel. Moreover, in real-world conditions, the thermal fluctuations of the CNT wall atoms impact the diffusive behavior of the adsorbed molecules, and must therefore be taken into account. This study performs a series of MD simulations to investigate the transport properties of hydrogen molecules confined within a narrow CNT with a diameter of 10.8 Å (~ 1 nm) at temperatures ranging from 100 ~ 800 K and particle loadings of 0.01~1 No/Å. To ensure the validity of the simulation results, the MD model assumes the tube to have a flexible wall. Hydrogen molecules are treated as spherical particles. In performing the simulations, the hydrogen molecules are assumed to have a perfectly spherical shape. In addition, the interactions between the molecule and the CNT wall atoms and the interactions between the carbon atoms within the CNT wall are modeled using the Lennard-Jones potential [25,2. The simulations focus on the hydrogen adsorption within the SWNT not adsorption in the interstices or the external surface of nanotube bundles.

Sorption and surface flow in graphitized carbon membranes - I. The steady state

1967 ◽  
Vol 299 (1459) ◽  
pp. 434-454 ◽  
Keyword(s):  
Gas Phase ◽  
Diffusion Coefficients ◽  
Surface Flow ◽  
Inert Gases ◽  
Sulphur Hexafluoride ◽  
Carbon Membranes ◽  
Carbon Particles ◽  
Influence Of Temperature On ◽  
Pass Through ◽  
The Individual

A study has been made of the flow of inert gases and of sulphur hexafluoride through, and of the adsorption of argon and sulphur hexafluoride on, two carbons chosen for the energetic homogeneity of the sorbing surfaces and non-porosity of the individual carbon particles. A wide temperature range has been covered, ‘surface’ and ‘gas phase’ flows of the sorbed gases have been measured using helium as non-sorbed calibrating gas, and the corresponding permeability and diffusion coefficients derived. The smooth, non-porous sorbents chosen were able to produce extra flows considerably greater than those on much larger but porous and broken surfaces of some other sorbents (e. g. active carbons and alumina-silica cracking catalyst). The concentration dependence of the surface diffusion coefficients, D ss , agrees with a treatment of this dependence according to which, in the regime when gas phase diffusion coefficients are independent of pressure, D ss varies inversely as the slope of the isotherm. When fluxes at each of a series of pressures are plotted against temperature, the fluxes pass through maxima as the temperature is lowered. This behaviour can be explained in terms of the simultaneous influence of temperature on D ss and on the concentration gradients.

Molecular-Dynamics Studies of the Diffusion of H2 in All-Silica ZSM-5

2011 ◽  
Vol 704-705 ◽  
pp. 401-406
Author(s):  
Xiao Ming Du ◽  
Yao Huang ◽  
Er Dong Wu
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficients ◽  
Molecular Hydrogen ◽  
Pressure Range ◽  
Hydrogen Diffusion ◽  
Structural Difference ◽  
Dynamics Simulation ◽  
The Difference ◽  
Increasing Temperature ◽  
Diffusion Properties

Molecular dynamics (MD) techniques were employed to simulate the diffusion properties of molecular hydrogen on all-silica ZSM-5 zeolite. The results indicated that in the temperature range of 77-293K and the pressure range of 14-3360 kPa, the diffusion coefficients are found to range from 1.2×10-9m2/s to 3.8×10-7m2/s, and increase with increasing temperature, and decrease with increasing pressure. The activated energy for hydrogen diffusion determined from the simulation is pressure-dependent. The diffusion of the molecular hydrogen in all-silica ZSM-5 zeolite channels is anisotropic duo to the increase of the temperature. The diffusion coefficients in straight channels are higher than that in zigzag channels. The difference results from the structural difference of the two channels and the different loadings of hydrogen. Keywords: Hydrogen; Zeolite; Diffusion; Molecular-dynamics simulation

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