Conversion from c6 and c12 = 0 to sigma epsilon

From: Sourav Ray (
Date: Sat May 14 2016 - 06:29:49 CDT


For two particles without LJ interaction, the c6 and c12 values (in GROMACS
topology file) are set to 0. If I would like to incorporate the same to a
CHARMM parameter file, I need to convert them to sigma-epsilon form.

Since the usual conversion formula will result in 'divide by 0' error. I
presume we can set epsilon = 0 and sigma to some arbitrarily high value
well beyond the LJ cut off (or any random value because epsilon is zero),
any suggestions?

Thanks and regards

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