[gmx-users] LJ potential definitions?

[Anton Feenstra]

Hi All,


I am trying to figure out some strange desagreement between LJ potential
definitions.

 From the Gromacs manual (p50/51) I have:

	E(r) = 4? ( (?/r)^12 - (?/r)^6 )

but from Cornell et al. (& Kollman), JACS 117 (1995), eq. 1, I have:

	E(r) = A/(r^12) - B/(r^6)
where (from Table 13):	A = ? ?^12 and B = 2? ?^6
(they use R for r and R* for ?)
Rewriting this, gives the following:

	E(r) = ? ( (?/r)^12 - 2 (?/r)^6 )

So the question is, compared to the 'Gromacs' formula, where did the
factor 4 in 4? go, and second, where does the factor 2 for the sixth
power term come from?


-- 
Groetjes,

Anton
  ________ ___________________________________________________________
|        | Anton Feenstra                                            |
| .      | Dept. of Pharmacochemistry - Vrije Universiteit Amsterdam |
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| ' __   | Feenstra at chem.vu.nl - http://www.chem.vu.nl/afdelingen/FAR|
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| (    ) | Dept. of Biophysical Chemistry - University of Groningen  |
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