AMBER Archive (2002)

Subject: Re: van der Waals, hydrogen bond energy

From: Andreas Svrcek-Seiler (svrci_at_tbi.univie.ac.at)
Date: Sat Jun 29 2002 - 07:29:38 CDT

Hi,
> Dear Amber users:
>
> I did a minimization on a system without solvent, and
> the van der Waals energy was negative while hydrogen
> bond energy was zero from sander's output. But after I
> added water box, the van der Waals energy became
> positive and hydrogen bond energy was still zero, even
> after the system was heated up. Does anyone know why?
...The hydrogen bond energy is zero, because
the 'current' force field parameters know no '10-12' terms
that took care of hydrogen bonds in 'older' force field versions.
positive VdW energy seems to be a trait of water (at least of TIP3P
water as long as it's liquid (or 'frozen')).
best regards
Andreas 

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