[gmx-users] about (painful) units conversion

Nicolas SAPAY nsapay at ucalgary.ca
Mon Jul 10 23:39:36 CEST 2006

I'm still working on the CHARMM ff convertion into the Gromacs standards
and I wonder how exactly to convert kcals of CHARMM in to Gromacs'
KJoules. I have found 3 different constants (at least?)
- officially (SI) : 1 kcal = 4.1868 kJ
- but often : 1 kcal = 4.184 kJ
- in my graduate courses of thermodynamics = 1 kcal = 4.185 kJ

Who's right? It's probaly a debat with no end and the three answers are
probably correct ;-). But which conversion should be applied in our case?


[ Nicolas Sapay Ph.D. ]
University of Calgary, Dept. of Biological Sciences
2500 University Dr. NW, Calgary AB, T2N 1N4, Canada
Tel: (403) 220-6869
Fax: (403) 289-9311

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