[gmx-users] FEP softcore problematics

[Maik Goette]

Hi all

Because the fact of handling vdw and electrostatics with the same values 
was discussed before, I won't go into much detail about what Berk and 
David M. wrote.
I changed the code to apply different alpha values for vdw and 
electrostatics. Now I am able to e.g. calculate vdw with an alpha=1 
(l-power linear or squared) and qq with alpha=0 (always linear, if alpha 
!= 0).
What I see are lincs errors after 40% of the sim-time in the upper case.
Is it because of the fact, that vdw are treated soft and qq hard?
With alpha=2 for qq it works, but still yields large fluctuations at 
lambda=0 & 1.

Any suggestions?

Regards
-- 
Maik Goette, Dipl. Biol.
Max Planck Institute for Biophysical Chemistry
Theoretical & computational biophysics department
Am Fassberg 11
37077 Goettingen
Germany
Tel.  : ++49 551 201 2310
Fax   : ++49 551 201 2302
Email : mgoette[at]mpi-bpc.mpg.de
         mgoette2[at]gwdg.de
WWW   : http://www.mpibpc.gwdg.de/groups/grubmueller/