I'm alchemically transforming K+ into Na+ in a water box using CHARMM36 force field. I got the solvation free energy difference between K+ and Na+ -23.40 Kcal/mol while in one research publication (VB Luzhkov et al. Biochim Biophys Acta 1548 (2), 194-202. 2001 Aug 13) they have shown -17.33 Kcal/mol solvation free energy difference between K+ and Na+ using programme Q with GROMOS 87 force field.
What can be the reason of this difference ?
I appreciate your suggestions.
Edited by abhi (01/08/17 01:16 AM)