[gmx-developers] doing energy evaluations at alternate lambda values (i.e. for bennett acceptance ratio)

[David Mobley]

Berk,

>  From your mail it seems as if your bonded interactions do not influence
> dvdl,
> then you can also not calculate bonded interactions, this also makes
> sure the bonded
> forces are not double counted.

I am not sure what you mean by the bonded interactions not influencing
dvdl? And actually, what I am interested in here is the total
potential energy, not dvdl: I want the correct total potential energy
for the timestep I am at, at the lambda value of interest. I don't
want to have to assume I am not changing any bonds as a function of
lambda: This isn't something I want to use just for one particular
application; rather, a bunch of folks will be doing free energy
calculations with GROMACS, and will switch to using this approach for
calculating the free energy differences, so it needs to be fully
general.

> The only thing I am not sure of is if the virial is not overwritten.
>
> For efficiency you also want to call only the free-energy energy loops
> in nonbonded.c
> for the other lambda values.


What do you think of the approach Erik discussed in his mail?

Thanks,
David

> Berk.
>
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