[gmx-users] Re: Question about CCl4 box!

[David]

On Sat, 2003-05-03 at 14:40, PeiQuan Chen wrote:
> Dear gmx-users:
> >Alternatively you can leave out one of the constraints. You will still
> >get the same geometry, since the constraint problem is completely
> >determined by 9 inequalities. You can leave out any of the 10
> >constraints
>    I have leaver out one of the constraints( 4 5 ).
>    Now that I can reproduce the exp data of density and DHvap
>    
>    Density: exp.(1.594) cacul.(1.572)
>    DHvap:   exp.(32.54kJ/mol ) cacul.( 32.38kJ/mol)
> 
>    But I can't still the make the tau_p value more smaller.If I make the value smaller.
> The problem is the same as I have report.
>    
>    I want to ask how to change the tau_p smaller and the simulation doesn't carsh. 

OK, that looks good, experimental values reproduced within 1%. If you
really want a shorter tau_p you probably need a larger box. Shorter
tau_p means smaller pressure fluctuations, but larger box fluctuations.
This is probably why your runs crash, because box < 2 cutoff.

However, if you do a run of 1 ns or so, you'll probably see that your
average pressure is correct, and that is what matters I'd say.
-- 
Groeten, David.
________________________________________________________________________
Dr. David van der Spoel, 	Dept. of Cell and Molecular Biology
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://xray.bmc.uu.se/~spoel
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