From: Sichun Yang (syang_at_physics.ucsd.edu)
Date: Sun Feb 29 2004 - 22:48:15 CST
Thank you for your explanation, again, Jerome.
On Sun, 29 Feb 2004, [iso-8859-1] Jérôme Hénin wrote:
> Le dimanche 29 Février 2004 01:32, vous avez écrit :
> > Thank you for your explanation, Jerome.
> > However, How can I understand a negative GPRESSURE?
>
> The pressure is computed as two components : the kinetic part is identical to
> the ideal gas pressure (ie kT/nV - this one is of course positive, and nearly
> constant), and the dynamic part, often computed using a virial expression (a
> sum on all atoms of force_on_atom scalar position_of_atom). This second part
> is the one with large fluctuations (which are smaller if you consider atom
> groups rather than isolated atoms, that is, "group pressure"), and it takes
> either positive or negative values.
> Physically speaking, a system of interacting particles has a negative pressure
> whenever it tends to shrink rather than to expand - this never happens to an
> ideal gas, of course.
>
> Cheers,
> Jerome
>
> --
> Jérôme Hénin
> Equipe Dynamique des Assemblages Membranaires
> Université Henri Poincaré / CNRS UMR 7565
> B.P. 239 54506 Vandoeuvre-lès-Nancy Cedex
> Tel : (33) 3 83 68 43 95 Fax : (33) 3 83 68 43 71
> http://www.edam.uhp-nancy.fr/
>
> In principio creauit Linus Linucem
>
>
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