[gmx-users] Gibbs Energy Calculation and charges

Christopher Neale chris.neale at mail.utoronto.ca
Thu Oct 17 05:15:22 CEST 2013

Ah, I see. I guess that you are using couple-intramol = no (the default in v4.6.3 at least). That means
that the intramolecular charge-charge interactions are always at full-strength (and therefore different).

I would expect that normal at lambda=0 should be the same as double at lambda=0.5 only for
couple-intramol = yes

If you were using couple-intramol = yes already, then I am as confused as you are.


-- original message --

You are correct in the first part of your statement, part that isn't correct is I expect for the same charge on the atom I expect it to give the same dH/dl value.

For example, for the OE atom that I provided the graphs for ( http://ozreef.org/stuff/octanol.gif and http://ozreef.org/stuff/water.gif )

Lambda       Normal
0.0000	-0.5310
0.0000	-1.0620
0.5000      -0.5310

Therefore, the normal charge molecule when lambda = 0 should be identical to that double charge one when lambda = 0.5.  They should be the same in all manners, LJ, bonds, charges etc.

So would I not expect to get the same dH/dl value out?

Catch ya,

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