[gmx-users] Free Energy Calculation: dVpot/dlambda is always zero

[Justin A. Lemkul]

Anirban Ghosh wrote:
> 
> Hi ALL,
> 
> I am trying to run free energy calculation and for that in the md.mdp 
> file I am keeping the following option:
> 
> ; Free energy control stuff
> free_energy     = yes
> init_lambda     = 0.0
> delta_lambda    = 0
> sc_alpha        =0.5
> sc-power        =1.0
> sc-sigma        = 0.3
> 
> 
> But still I find that in my log file the values for dVpot/dlambda is 
> always coming to be zero.
> What I am doing wrong?
> Any suggestion is welcome. Thanks a lot in advance.
> 

You haven't indicated your Gromacs version, but assuming you're using something 
in the 4.x series, you're not specifying the necessary parameters to do any sort 
of transformation, particularly couple_lambda0 and couple_lambda1.  If left at 
their default values (vdw-q), nothing gets decoupled.

-Justin

> 
> Regards,
> 
> Anirban
> 

-- 
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Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
MILES-IGERT Trainee
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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