Re: [AMBER] Setting forcefield parameters

From: Jason Swails <>
Date: Fri, 13 Sep 2013 10:03:21 -0400

On Fri, Sep 13, 2013 at 9:44 AM, Tanmoy Paul <> wrote:

> Hi,
> I am doing ONIOM calculations for RESP charge setup using gaussian
> 09. Now during optimization the VDW parameters for HW and HO are asked
> to be set as they are being set to zero in 'amber.prm' incorporated
> to gaussian 09.

That is because they _are_ set to 0 in most versions of the Amber force

The idea is that the hydrogen is completely enclosed in the vdW radius of
the oxygen atom it is bonded to.

I have searched for the missing parameters in AMBER12
> parm . I have found two different VDW radius for HO ( one in
> 'parm99EP.dat' and another in 'parmpol12.dat') and no parameter
> corresponding to HW. I am confused regarding which one to pick for HO
> and where to find the parameters for HW.

Look in parm99.dat or parm10.dat or something like that. You are looking
at the polarizable force field parameter files (parmpol12.dat) and the
extra points (lone pairs)-based force field (parm99EP.dat). I believe that
ONIOM uses the standard, 'fixed-charge' force field.


Jason M. Swails
Rutgers University
Postdoctoral Researcher
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Received on Fri Sep 13 2013 - 07:30:02 PDT
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