Compiled list of free energy features/efforts people want to put in/revise in GROMACS

A compiled list of main issues that have been discussed in free energy calculations. If there is a sub-issue for a given topic, make the comments on that sub issue listed below, not here.

• Different softcore paths (in general, any variant of lambda dependent free energy kernel) - discussion is in #4011.

• Compilation of issues on improving output, specifically having data written to the .edr, not .dhdl directly, and controlling in what form the dhdl output appears - see issue #4012.

• Discussion of whether to include probability-interpolation thermodynamic states (enveloping distribution sampling, variational intermediates, etc) - discussion is in #4013.

• Multidimensional lambda functionality - discussion is in #4014.

• Compilation of issues on merging AWH and expanded ensemble functionality - discussion is in #4015.

Uncategorized points.

• Make functions alchemical-capable #3456 (closed) #3691 (closed) #2606 (closed)
• Make sure pull code working well with lambda functionality (#1303 (closed), may be mostly addressed)
• Interfacing PLUMED with alchemical calculations (mostly done in Shirts group).
• Making sure COLVARS is properly integrated.