scholarly journals Potential Landscape of a Probe Penetrant Particle for Fast Estimating of Silica Diffusion Properties

2021 ◽  
Vol 14 (3) ◽  
pp. 406-417
Author(s):  
Sergey V. Kukhtetskiy ◽  
Keyword(s):  
Energy Distribution ◽  
Diffusion Coefficients ◽  
Global Minimum ◽  
Percolation Cluster ◽  
Molecular Structures ◽  
Successful Search ◽  
Cluster A ◽  
Potential Landscape ◽  
Silicate Materials ◽  
Diffusion Properties

Successful search for optimal molecular structures of membrane materials requires efficient algorithms for assessing their diffusion properties. It is shown in this work that the potential landscape of a probe penetrating particle, a component that passes through the membrane during gas separation, is suitable for solving such problems. A number of indicators are considered that can be easily calculated from potential landscapes of specific models of silicate materials, both not related to the topology of the potential landscape (global minimum, voxel energy distribution), and depending on it (percolation cluster). A good correlation of these indicators with the corresponding diffusion coefficients is shown

scholarly journals Modification of boron nitride nanocages by titanium doping results unexpectedly in exohedral complexes

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Ruyi Li ◽  
Yang Wang
Keyword(s):  
Nitrogen Fixation ◽  
Boron Nitride ◽  
High Stability ◽  
Global Minimum ◽  
Molecular Structures ◽  
Collision Induced Dissociation ◽  
Experimental Production ◽  
Titanium Doping ◽  
Ti Doping ◽  
Bn Nanostructures

Abstract Despite their early experimental production and observation, the unambiguous molecular structures of metal-containing boron nitride (BN) nanocages still remain mysterious. It has been commonly assumed that this family of compounds has the metal atom confined inside the cage, just like their isoelectronic cousins, carbon metallofullerenes do. Here, we demonstrate that Ti(BN)n ($$n$$n = 12–24) complexes have, unexpectedly, an exohedral structure instead of an endohedral one, which could be verified by collision-induced dissociation experiments. The predicted global minimum structures exhibit some common bonding features accounting for their high stability, and could be readily synthesized under typical conditions for generating BN nanoclusters. The Ti doping dramatically changes not only the cage topology, but the arrangement of B and N atoms, endowing the resultant compounds with potential for $${\mathrm{CO}}_{2}$$CO2 capture and nitrogen fixation. These findings may expand or alter the understanding of BN nanostructures functionalized with other transition metals.

BO3 Molecular Structures: Examples of the Importance of Electron Correlation

2008 ◽  
Vol 73 (11) ◽  
pp. 1495-1508 ◽  
Author(s):  
Alexander Yu. Sokolov ◽  
Nathan J. Stibrich ◽  
Henry F. Schaefer
Keyword(s):  
Electron Correlation ◽  
Global Minimum ◽  
Isosceles Triangle ◽  
Molecular Structures ◽  
Basis Set ◽  
Oxygen Species ◽  
Higher Symmetry ◽  
Wide Range ◽  
Spectroscopic Identification ◽  
Correlation Consistent

In 1991 Burkholder and Andrews reported the spectroscopic identification of the boron- oxygen species BO, BO2, B2O2, B2O3, and BO2-. In addition, they tentatively identified two infrared features due to BO3. In this research, a wide range of possible BO3 structures is considered theoretically. The highest level of theory used involves the CCSD(T) method with an augmented correlation consistent quadruple zeta basis set. A planar structure O-B-O-O is predicted to be the global minimum, lying 4.2 kcal mol-1 below a higher symmetry (C2v) structure incorporating a BO2 isosceles triangle. Reasonable agreement is found between the theoretical vibrational frequencies and the two fundamentals reported by Burkholder and Andrews. The potentially important ozone adduct B-O3 is predicted to lie much higher in energy.

scholarly journals Thermometry in a Multipole Ion Trap

2020 ◽  
Vol 10 (15) ◽  
pp. 5264
Author(s):  
Markus Nötzold ◽  
Saba Zia Hassan ◽  
Jonas Tauch ◽  
Eric Endres ◽  
Roland Wester ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Md Simulation ◽  
Ion Trap ◽  
Linear Mapping ◽  
Trapped Ions ◽  
Translational Energy ◽  
Buffer Gas ◽  
The Finite Element Method ◽  
Potential Landscape

We present a characterization of the ions’ translational energy distribution in a multipole ion trap. A linear mapping between the energy distribution of the trapped ions onto the ions’ time-of-flight (TOF) to a detector is demonstrated. For low ion temperatures, a deviation from linearity is observed and can be attributed to the emergence of multiple potential minima. The potential landscape of the trapped ions is modeled via the finite element method, also accounting for subtleties such as surface-charge accumulation. We demonstrate the validity of our thermometry method by simulating the energy distribution of the ion ensemble thermalized with buffer gas using a Molecular Dynamics (MD) simulation. A comparison between the energy distribution of trapped ions in different multipole trap configurations—i.e., with hyperbolic rods, cylindrical rods, and cylindrical wires—is provided. With these findings, one can map the temperature of the trapped ions down to the Kelvin regime using their TOF distributions. This enables future studies on sympathetic cooling and chemical reactions involving ions in multipole traps.

Molecular dynamics simulation of multi-constituent gas diffusion properties in Venus atmosphere

2021 ◽  
Author(s):  
Wen Gao ◽  
Xiaoning Yang ◽  
Jing Wang ◽  
Quanwen Hou ◽  
Yanqiang Bi ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficients ◽  
Gas Diffusion ◽  
Dynamics Simulation ◽  
Diffusion Characteristics ◽  
Temperature And Pressure ◽  
Experimental Values ◽  
Dynamics Simulations ◽  
Interdiffusion Coefficients ◽  
Diffusion Properties

Abstract The purpose of studying the Venus’s atmosphere is to model and simulate Venus’s environment. One of the key parameters of the Venus’s atmosphere is diffusion coefficient. Experimental measurements of diffusion coefficients are particularly difficult under Venus’s environmental conditions. Molecular dynamics have become an important method for studying the properties and dynamics of microscopic systems. In this paper, the equilibrium molecular dynamics (EMD) simulations are used to calculate the interdiffusion coefficients of carbon dioxide (CO2) and nitrogen (N2) at room temperature and pressure in combination with Darken's equation. And the results are compared with experimental values and empirical equations to verify the rationality of the calculation method and the accuracy of the results. The interdiffusion coefficients of trace gases on the surface of Venus for the CO2 system in different states and the CO2-N2 interdiffusion coefficients with altitude in the Venus environment are given. The results show that the diffusion coefficients of the gases on the surface of Venus are two orders of magnitude smaller than those in the Earth's atmosphere and molecular dynamics simulations can well predict the diffusion characteristics of the Venus’s atmosphere and support the simulation of the Venus’s surface environment and the Venus’s atmosphere model.

scholarly journals An Indirect Approach for Correlation of Permeability and Diffusion Coefficients

2009 ◽  
Vol 283-286 ◽  
pp. 504-514 ◽  
Author(s):  
Khaled K. Al-Tarawneh ◽  
Olivier Buzzi ◽  
Kristian Krabbenhoft ◽  
Andrei V. Lyamin ◽  
Scott William Sloan
Keyword(s):  
Diffusion Coefficients ◽  
Filling Factor ◽  
Particle Diameter ◽  
Diffusion Test ◽  
Test Cost ◽  
Maximum Particle ◽  
Coefficient Of Uniformity ◽  
Different Grain Size ◽  
And Diffusion ◽  
Diffusion Properties

Diffusion tests in porous media are quite sensitive and long lasting procedures compared to permeability tests, which are usually more reliable and of shorter duration. Both diffusion and advection phenomena are dependent on the tortuosity of the material tested. A relevant question is to know whether it is possible to correlate permeability tortuosity p and diffusion tortuosity d. Several diffusion and permeability tests have been performed on non-uniform sand specimens having different grain size distribution. For each specimen, both the permeability and diffusion coefficients have been measured and two tortuosity factors (permeability and diffusion) have been back calculated. A theoretical model has been proposed to estimate d from p for a non-uniform granular material. The maximum particle diameter dmax is used to determine the maximum hydraulic diameter dh-max using the Hydraulic Radius Theory (HRT) for a 3D arrangement of spheres of same diameter dmax. Then, a filling factor  is applied to dh-max in order to capture the fact that smaller grains tend to fill the voids present in between the bigger particles. The filling factor is based on the coefficient of uniformity Cu. Relatively good results are obtained so that this model allows estimating the diffusion properties from a simple permeability test rapidly and at a fraction of the diffusion test cost.

Development of a Gas Method for Migration Studies in Fractured and Porous Media.

1992 ◽  
Vol 294 ◽  
Author(s):  
Kusti VÄÄtÄinen ◽  
Jussi Timonen ◽  
Aimo HautojÄrvi
Keyword(s):  
Porous Media ◽  
Liquid Phase ◽  
Gas Phase ◽  
Diffusion Coefficients ◽  
Tracer Gas ◽  
Phase Measurements ◽  
Apparent Diffusion Coefficients ◽  
Apparent Diffusion ◽  
Standard Techniques ◽  
Diffusion Properties

ABSTRACTA gas method for fast measurements of diffusion properties of porous materials has been developed. Diffusion coefficients in the gas phase are typically four orders of magnitude larger than those in the liquid phase. For samples whose structures do not change much upon drying it is possible to estimate the diffpision properties of the liquid phase when the properties of the gas phase are known. Advantages of the gas method are quick and easy measurements and therefore they can be used to optimize the liquid-phase measurements which may last months or years. For materials with good correlation between the gas and liquid-phase diffusion, the number of liquid phase measurements can be greatly reduced.Nitrogen was used as the carrier gas and helium as the tracer gas. Helium concentrations were measured by using standard techniques. The equipment was tested for two sample geometries, a column made of a polished granite slab and an acrylic slab with a flow channel in between, and a hollow bore core where diffusion occurs through the sample. Both types of measurement were modelled and apparent diffusion coefficients in the gas phase were determined.

scholarly journals INVESTIGATION OF ELECTRONS DIFFUSION COEFFICIENT DEPENDENCE ON TEMPERATURE IN PLASMA GAS CO2, N2, HE AND MIXTURES

2020 ◽  
pp. 31-41
Author(s):  
Nisaan Saud ORAIBI
Keyword(s):  
Experimental Data ◽  
Distribution Function ◽  
Diffusion Coefficient ◽  
Boltzmann Equation ◽  
Energy Distribution ◽  
Cross Section ◽  
Diffusion Coefficients ◽  
Equation Solution ◽  
Different Temperatures ◽  
Momentum Transfer Cross Section

The evolution of the μNth value at different temperatures was achieved through the drift velocity of electron. The results were show when the temperature was increased, the number of the electrons will be decreased because using the momentum transfer cross section for CO2 molecules through collisions. The calculation of the diffusion coefficient was used to deduce the μNth values of CO2 electrons at temperature between 288 to 573 k by utilization numerically the Boltzmann equation solution. The results were appearing the agreement with the theoretical and experimental data. Keywords: Diffusion Coefficients, Boltzmann Equation, Swarms Parameters, Energy Distribution Function.

On the Formation of Unusual Diffusion Profiles in CdxZn1-xTe Crystals after Implantation of Different Elements

2009 ◽  
Vol 289-292 ◽  
pp. 587-592 ◽  
Author(s):  
Herbert Wolf ◽  
F. Wagner ◽  
J. Kronenberg ◽  
Th. Wichert
Keyword(s):  
Diffusion Coefficients ◽  
Strong Dependence ◽  
The Other ◽  
Concentration Profiles ◽  
Transition Elements ◽  
Uphill Diffusion ◽  
Diffusion Behavior ◽  
The One ◽  
Diffusion Profiles ◽  
Diffusion Properties

It is known that the diffusion of Ag and Cu in Cd1 xZnxTe crystals exhibits unusual concentration profiles depending strongly on the external vapor pressure of Cd during diffusion. Recent experiments show that the dopant Na forms qualitatively the same diffusion profiles including the phenomenon of uphill diffusion. Also the transition elements Ni and Co show a strong dependence of the diffusion behavior on the external Cd pressure, but the shapes of the concentration profiles differ significantly from those known for Ag and Cu. The different behavior of Ag, Cu, and Na, on the one hand, and Ni and Co, on the other hand, are proposed to be connected to the respective charge states of the dopants at interstitial positions in Cd1 xZnxTe. For the dopants K and Au, unusual diffusion properties have not been observed. The respective diffusion coefficients are DK = 1.2(2)•10 10 cm2/s (750 K) and DAu = 8(2)•10 8 cm2/s (800 K).

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