CHARMM: VDISTANCE keyword in NBOND options

[Jeff Nauss <jnauss' at \`accelrys.com>]

 Within CHARMM, I came across a keyword VDISTANCE while examining some of
 the options for nonbonded specifications.  It is used as a suggested
 nonbonded specification in the CHARMM27 force field as well as the
 Momany
 and Rone force field.
Researching that option, I found in old c24 documentation that it is a
 "distance specified Van der Waal function" with no further
 explanation.  I
 could not find any mention of VDISTANCE in the c27 documentation.  In
 my
 tests with the option, there appears to be no effect on the
 calculations.
 Might anyone have any further information?  Might it be a mere fossil or relic?
 Thank you in advance...
 --
 Jeffrey L. Nauss, PhD		Phone: (858) 799-5555
 Life Science Customer Training 	Fax: (858) 799-5100
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