[gmx-users] Some questions about free energy calculation

[nicolis at guideo.fr]

Many thanks to both Davids :-) for the answers.
I am in the reading of a lot of papers.
Let me ask a little more questions as it is the first time I try the FEP 
calculations.
I see in the literature that in general we equilibrate the system a few ps for 
each lambda value and than collect the data for the averages.
In gromacs however, if I define a init_lambda, delta_lambda and nsteps, I 
see that lambda changes by delta_lambda at each step, going from 
init_lambda to init_lambda+delta_lambda*nsteps.
I understand that if I choose init_lambda=0 and delta_lambda=1/nsteps I 
change from topology A to topology B, but without prior equilibration for 
each lambda value and no "data collection" at each lambda. Is it a 
different approach or it ends to the same DG if the delta_lambda is small 
enough?
Is the DG the -kT ln<e^(E/kT)> computed by g_energy with the option -fee 
for the dVpot/dlambda? And I have to apply the Born correction on that 
value, am I correct?
And the -kT ln<e^(E/kT)> computed by g_energy with the option -fee for the 
dEkin/dlambda should be zero?

Thanks again.

Yiannis