AMBER Archive (2009)

Subject: Re: [AMBER] SPC/E HOH angle

From: case (
Date: Fri Oct 30 2009 - 07:51:41 CDT

On Fri, Oct 30, 2009, Hemant Kumar wrote:

> I am trying to do some simulation with spc/e water using parm99 ff using
> AMBER10.
> To change default water parameter value from TIP3P to SPC/E,I need to
> source frcmod.spce file which is supossed to change angle bond etc
> paramters.
> But frcmod doesn't have any term HOH angle which is diffrent from
> TIP3P(104 vs 109). then how leap takes correct bond angle for prmtop file?
> Am I missing something?

Amber uses three bonds (two O-H and one H-H) to construct the rigid
three-point model for SPC/E or TIP3P. The angle terms are removed from the
waters. Hence, it is the H-H distance that determines the H-O-H bond angle.


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