Those parameters don't matter. TIP4PEw is a rigid water model which means
it only behaves "correctly" when used with SHAKE (or SETTLE), meaning the
geometry is constrained to the equilibrium geometry of the water model.
Parameters involving virtual sites are even more meaningless, since virtual
site positions are defined within a given reference (as a function of the
positions of other particles). I'm pretty sure that bonded forces between
virtual sites and other atoms are not computed, and the dummy values here
just satisfy tleap requirements, I think.
HTH,
Jason
On Wed, Feb 16, 2022 at 11:40 AM Rosemary Millmore <rosiemantell.gmail.com>
wrote:
> Hi,
>
> In the frcmod files for various four-point water models, there are some
> parameters that have zero force constant or torsional barrier height. For
> example, in tip4pew there are:
> HW-OW-EP 0.0 120.0
> HW-HW-OW 0. 127.74
> X -HW-OW-X 2 0.0 0.0 1.0
>
> Do these parameters serve any purpose in the software?
>
> Thank you,
>
> Rosemary
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--
Jason M. Swails
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Received on Wed Feb 16 2022 - 09:30:02 PST
