[gmx-developers] calculating dielectric constant

[Qiao Baofu]

Hi all developers,

I have posted this problem on the gmx-user list. David gave me some
suggestions, but the problem has not been solved completely.

I simulated an ionic liquid [mmimCl], 981 molecules for 1.5 ns, every 5 time
steps saved.  In the .mdp file, I used PME:{ coulombtype  = pme; epsilon-r =
1}, the simulation temperatuer is 425K.

Then I used  "g_dipoles -temp 425 -f -s -enx" to calculate the the
dielectric constant, the result is: Epsilon = 826.496. I checked the
epsilon.xvg, in which the result is converged to some extent with some
fluctuations at the end.  I think the result is too big. Even though I have
no exerimental data for [mmimCl] at hand, I have some reported data of some
other ionic liquids, 10-20.

Is there anyone who can give some suggestions? Great thx!

-- 
Sincerely yours,
**********************************************
Baofu Qiao, PhD
Frankfurt Institute for Advanced Studies
Max-von-Laue-Str. 1
60438 Frankfurt am Main, Germany TEL:+49-69-7984-7529
**********************************************
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