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

[David Mobley]

Dear all,

We're attempting to modify mdrun to be able to write out the system
total potential energy evaluated at a number of alternate lambda
values during a free energy calculation, when energies are written to
output. (The goal is to use this output for doing free energy
calculations with Bennett Acceptance Ratio or other methods which
require potential energies evaluated at a variety of alternate lambda
values).

I'm assuming this would be a straightforward (perhaps 20 minutes?)
task for anyone who already knows the inner workings of the code, but
since I'm not that familiar with it, it seems a bit more difficult for
me. Is there anyone who wants to volunteer?

If not, can anyone help by telling me the complete set of function
calls that need to be done in the inner loop of do_md(), in order to
safely:
1) Change the current lambda value to some other lambda'
2) Compute the new total energy
3) Restore lambda to its original value so the simulation can continue.

Thanks very much in advance.

Sincerely,
David Mobley
UCSF