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March 18, 2004, 07:39 
about LJ Characteristic Length

#1 
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Who can tell me what is the LJ Characteristic Length and LJ Energy Parameter in the fluent software? How can I get the details about them, thank you very much!!!!!


March 18, 2004, 15:42 
Re: about LJ Characteristic Length

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I accidentaly worked some time ago on Molecular Dynamics problems, so I should be able to answer this one..
Well, LJ stands for LennardJohnson 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, 5th edition, John Willey & Sons Ltd., 1976) 

March 19, 2004, 02:23 
Re: about LJ Characteristic Length

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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 LJ potential, but how can i get the LJ Characteristic Length and LJ 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!


March 22, 2004, 20:53 
Re: about LJ Characteristic Length

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Kevin, Look at the transport database from Chemkin. The LJ parameters for many species are listed in there.


March 22, 2004, 21:00 
Re: about LJ Characteristic Length

#5 
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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!


March 23, 2004, 09:07 
Re: about LJ Characteristic Length

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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@


March 23, 2004, 17:53 
Re: about LJ Characteristic Length

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Hi Kevin, I wonder why are you taking such trouble investigating LJ 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 

March 24, 2004, 22:53 
Re: about LJ Characteristic Length

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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!


March 25, 2004, 09:33 
Re: about LJ Characteristic Length

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Hello! Everyone ,I met the problem about the Arrhenius Rate 1.How to get the PreExponential 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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