[gmx-users] short and long range coulomb with pme

[David van der Spoel]

On Mon, 29 Apr 2002, Erik Lindahl wrote:

>No, the problem is that it isn't possible to separate group 
>contributions in the PME algorithm. I'm pretty sure it says that 
>somewhere in the manual too :-)

Actually I just submitted a manuscript with a workaround. The trick is
quite simple, you use tpbconv to make one group, e.g. the Ca++ have zero
charge, and the you use the mdrun -rerun option to rerun your trajectory.
Now you will get the PME energy for SOL-SOL. If you have multiple ions,
you can then set the charges of the solvent to 0 and mdrun -rerun again.
That will give you the PME energy for Ca-Ca.
Now the interaction energy Ca-SOL is the difference between the original
PME energy and that from the two reruns.

Groeten, David.
________________________________________________________________________
Dr. David van der Spoel, 	Biomedical center, Dept. of Biochemistry
Husargatan 3, Box 576,  	75123 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://zorn.bmc.uu.se/~spoel
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++