[gmx-users] dg/dl unit
c.oostenbrink at few.vu.nl
Thu Nov 3 10:54:53 CET 2005
>>I am just wondering what the units for dg/dl mean in a free energy
>>perturbation run. I get a graph of dG/dl (KJmol-1nm-2l-1) vs time (ps).
>>Now, ideally i want KJmol-1lambda-1 vs lambda graph so that i can integrate
>>it to get back a value that is KJ/mol.
>>I am just wondering what (nm-2l-1) unit means and if it is related to ps as
>This was an error, it should be KJmol-1lambda-1 (the data is correct).
>This has been corrected in Gromacs 3.3.
Can I ask a naive question? Since when is lambda a unit? lambda is a
unitless quantity and quantities usually do not appear in a unit. If you
want to do it completely correct, I think that dG/dl has the unit kJmol-1.
If you would do a slow growth simulation in which you modify lambda as a
function of time, then you probably write out dG/dl * dl/dtime and the
unit would be kJmol-1ps-1.
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