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Old   March 18, 2004, 06:39
Default about L-J Characteristic Length
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KEVIN
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Who can tell me what is the L-J Characteristic Length and L-J Energy Parameter in the fluent software? How can I get the details about them, thank you very much!!!!!
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Old   March 18, 2004, 14:42
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George
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I accidentaly worked some time ago on Molecular Dynamics problems, so I should be able to answer this one..

Well, L-J stands for Lennard-Johnson potential, which describes the mutual forces that exist among atoms in a molecule. You can look in any textbook on solid state physics or kinetic theory of gases. (E.g. a classical reference from the first area: KITTEL, C.: Introduction to Solid State Physics, 5-th edition, John Willey & Sons Ltd., 1976)
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Old   March 19, 2004, 01:23
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KEVIN
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Thank you very much, George. I get the book which you mentioned in the message. It just tells me what is the L-J potential, but how can i get the L-J Characteristic Length and L-J energy parameter. Do you know where i can get these parameters, or i have to calculate them according some formulations, and what's form of these formulations? Thank you,very very much!
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Old   March 22, 2004, 19:53
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cg
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Kevin, Look at the transport database from Chemkin. The L-J parameters for many species are listed in there.
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Old   March 22, 2004, 20:00
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KEVIN
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cg,thank you very much! Can you tell me whether the chemkin is a software or a book? thanks a lot!
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Old   March 23, 2004, 08:07
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KEVIN
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thank you very much! i have got the answer from the chemkin. i have another question, what's the degrees of the freedom, where can i get the details about it? thank you very much@
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Old   March 23, 2004, 16:53
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George
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Hi Kevin, I wonder why are you taking such trouble investigating L-J potentials? Firstly, because the parameters (except perhaps for the number of degrees of freedom) are by no means possible to derive by you alone. And secondly, you need them only in order to be able to use kinetic theory of gases option for calculation of some physical properties. However, experimental data are substantially more accurate, namely if the database offers polynomial or piecewise polynomial approximation.

Regards George
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Old   March 24, 2004, 21:53
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KEVIN
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Hello! Everyone , now i simulate a chemical reaction between gas(nh3) and porous solid(cacl2),but i met a problem in defining the material property. In the fluent, the unit of the standard state enthalpy and standard state entropy is j/kgmol and j/kgmol.k,respectively. But i search the unit of the stand state enthalpy and standard state entropy is j/mol and j/mol.k respectively. Who can tell me how to switch between these two units? Thank you very much!
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Old   March 25, 2004, 08:33
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kevin
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Hello! Everyone ,I met the problem about the Arrhenius Rate --1.How to get the Pre-Exponential Factor --2.How to calculate the Activation Energy --3.How to calculate Temperature Exponent

PS:I simulate the chemical reaction between the gas(nh3) and solid(cacl2)

Thank you very much!!!!
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