[gmx-developers] calculating dielectric constant

[David van der Spoel]

Qiao Baofu wrote:
> 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!
> 
Do you mean the other liquids have dielectric constant 10-20?
Or do you have 10-20 data poinst for other liquids.

Either way, try one of the other liquids to test it.

-- 
David.
________________________________________________________________________
David van der Spoel, PhD, Assoc. Prof., Molecular Biophysics group,
Dept. of Cell and Molecular Biology, Uppsala University.
Husargatan 3, Box 596,  	75124 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://folding.bmc.uu.se
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++