From: Bill Ross <ross.cgl.ucsf.EDU>
Date: Mon, 22 Nov 2010 09:36:05 -0800

> You can also change the bond force constants, but TIP3P is defined
> strangely (O-H, O-H, and H-H bonds to maintain geometry), with no
> VDW parameters on the H atoms. They are designed to be treated with
> SHAKE, or you'll probably get H-atoms collapsing into a strongly
> negative atom.

Alternatively the vdw-less H might extend beyond the vdw of the O into
another negatively-charged atom, similarly leading to fusion and
divide-by-0 or other mathematical artifact. TIP3 waters are designed
to use SHAKE to avoid such problems.


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Received on Mon Nov 22 2010 - 10:00:04 PST
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