Amber TI parser should provide dimensionless dH/dl

[orbeckst]

The current implementation of the Amber TI parser (amber.extract_dHdl) returns a dataframe with native Amber units (as used to be the case in alchemical-analysis) instead of the prescribed reduced dHdl standard form: the potential energy derivatives should be divided by 1/kT.

See for example

alchemlyb/src/alchemlyb/parsing/gmx.py

Line 132 in e5b2e58

dHdl = beta * dHdl

Todo:

• amber.extract_dHdl() needs additional temperature T argument
• make data dimensionless (something like dHdl = beta * dHdL with beta = 1/(kB*T)
• adjust tests

(See also #56 )

[orbeckst]

@shuail sorry, this slipped through when I was reviewing earlier. We need to make sure that all parsers produce the same dataframes, though, so this is a necessity.

[shuail]

Got it, will take a look soon

[orbeckst]

@dotsdl I know you're busy (GitHub displays status nowadays?!?) but because we talked about it, I am tentatively assigning you to this issue and #56 . Maybe @shuail can give input when needed.