Re: AMBER: BUG? Does TLEAP understand SPC/E water?

From: David A. Case <>
Date: Fri, 1 Jun 2007 11:37:10 -0700

On Fri, Jun 01, 2007, David Cerutti wrote:
> When I change a leaprc file to reference the SPC water in solvents.lib
> rather that TIP3P, by adding the following lines:
> rather than "HOH = TP3" / "WAT = TP3" as the default seems to be, it seems
> that this should direct TLEAP to look in the same solvents.lib file where
> it finds the TIP3P parameters and find instead the SPC/E parameters and
> put those in the topology wherever it finds water in the simulation.

LEaP does exactly what you describe. But
you also need to load the spce parameters explicitly:

loadamberparams frcmod.spce

[See section 2.11 of the Users' Manual. It's not clear from you message
whether you did this step or not, but it sounds like you may not have.]

> The part I'm scratching my head about is that it DOES obtain the
> correct charges

I assume(?) this is because you had some command like

solvatebox x SPCBOX ....

rather than using TIP3PBOX above. The charges are stored in the solvents.lib
file, whereas the lennard-jones and bonding parameters are stored in frcmod

...hope this helps...dac
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Received on Sun Jun 03 2007 - 06:07:39 PDT
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