Force between two gas atoms

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Paul - 17 Jul 2008 19:11 GMT

Hi,

Is it correct to say that according to Lennard-Jones potential simple
mathematical model the force between two noble gas atoms far apart
from each other is ~ 1/r^6 and ~ 1/r^12 for near distances? The full
equation is found at,

http://en.wikipedia.org/wiki/Lennard-Jones_potential

The equation is used for a simulation consisting of noble gas atoms
inside a tank. If there's a better equation then I would greatly
appreciate someone posting the equation.

Thanks,
Paul

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Androcles - 17 Jul 2008 19:47 GMT

| Hi,
|
| Is it correct to say that according to Lennard-Jones potential simple
| mathematical model the force between two noble gas atoms far apart
| from each other is ~ 1/r^6 and ~ 1/r^12 for near distances?

Nope. The correct values are 1/r^(6.02323412 +/- 0.00034342344)
and 1/r^(11.87482352 +/- 34.243345535)
but any approximation will do because it is a simple model hence it
is approximate to the true Jones-Lennard potential. Also Jones comes
alphabetically before Lennard.

The full

| equation is found at,
|
| http://en.wikipedia.org/wiki/Lennard-Jones_potential

Indubitably written by Jones and Lennard or there associates in
wackypedia, the crap anyone can write.

| The equation is used for a simulation consisting of noble gas atoms
| inside a tank.

But fails miserably when the simulated atoms are inside a simulated
armoured personnel carrier.

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Uncle Al - 17 Jul 2008 19:53 GMT

> Hi,
>
[quoted text clipped - 8 lines]
> inside a tank. If there's a better equation then I would greatly
> appreciate someone posting the equation.

Compare with van der Walls attraction.

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Paul - 17 Jul 2008 20:23 GMT

> > Hi,
>
[quoted text clipped - 10 lines]
>
> Compare with van der Walls attraction.

I appreciate it. What book(s) would you recommend for the topic?

Regards,
Paul

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Uncle Al - 17 Jul 2008 22:39 GMT

> > > Hi,
> >
[quoted text clipped - 12 lines]
>
> I appreciate it. What book(s) would you recommend for the topic?

<http://en.wikipedia.org/wiki/Van_der_Waals_forces>
Start here.

There's a whole pile of attractive and repulsive forces.
Leonard-Jones is a simplified case - OK for helium but not necessarily
for argon (dispersion forces as stated) and probaby not for xenon
(large polarizability).

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Natural Science Forum / Physics / General Physics / July 2008

Force between two gas atoms