[gmx-users] Very large fluctuations in dg/dl

[Patrick Fuchs]

Hi Stephane,
just to finish with this story, I took the value 54 determined in 
(Hunenberger & van Gunsteren,1998,J Chem Phys; Smith & van Gunsteren, 
1994, J Chem Phys), that has been updated to 61 since then. But as 
stated by Berk and Lars it will hardly make any difference in the 
properties I'm interested in.
Ciao,

Patrick

Stéphane Téletchéa a écrit :
> Patrick Fuchs a écrit :
>> Hi Gromacs users,
>> I have a few questions related to solvation free energy calculation via
>> thermodynamic integration.
> 
>> #ifdef FLEX_SPC
>> #include "flexspc.itp"
>> #else
>> #include "spc.itp"
>> #endif
> 
>> coulombtype            = generalized-reaction-field
>> rcoulomb               = 1.4
>> rvdw                   = 1.4
>> epsilon_rf             = 54.0
> 
> I cannot state for other parameters, but i'm surprised for the 
> (relatively?) low value for epsilon_rf used here.
> 
> For instance in Geerke and van Gunsteren (ChempPhysChem 2006, 7, 
> 674-678), the value used for reaction-field (not generalized) is 61 for 
> SPC water (referring to Heinz, van Gunsteren & Hunenberger, J Chem Phys 
> 2001, 115, p1125-1136).
> 
> Is this value a special case for 'generalized-reaction-field' ?
> 
> Thanks in advance for clarifications.
> 
> Stéphane
> 

-- 
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Patrick FUCHS
Equipe de Bioinformatique Genomique et Moleculaire
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