namd coulomb conversion factor

From: Mohan maruthi sena (
Date: Sat Sep 27 2014 - 01:09:43 CDT

Hi all,
           I want to calculate coulomb energy between two point
charges of +1 each. I do not use any periodic boundary conditions or
pme. The distance between two charges is 9.29 angstorms. When i run
for one step and calculate coulomb energy as q1* q2/(4*pi*r), I get a
value of 0.0085. The reported value in namd output file is
0.6661 kcal//mol. I considered epsilon value as 1, Is there any
conversion factor that namd uses to convert coulomb/ansgstorm to
kcal/mol? Can you please explain about the conversion factor.

Thanks & Regards,

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