how to understand vdwForceSwitching

From: Liqun Zhang (
Date: Sat Feb 11 2012 - 17:09:48 CST

Dear namd users:

I read the namd manual online. I found that the explanantion for
vdwForceSwitching and switching was not clear. I copied the explanation as

If switching is turned on, then smoothing functions are applied to both the
electrostatics and van der Waals forces;

If both switching and vdwForceSwitching are set to on, then CHARMM force
switching is used for van der Waals forces. *LJcorrection as implemented is
inconsistent with vdwForceSwitching.

Based on the figure shown, after turning on switching, the energy and
distance figure should be continuous (energy reaches 0 at cutoff distance).
After turning on both switching and vdwForceSwitching, the energy and
distance figure should still be continuous. But what is the difference?
What is the meaning for CHARMM force switching? Thanks a lot.



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