AMBER Archive (2009)

Subject: Re: [AMBER] AMBER External keyword

From: Gustavo Seabra (gustavo.seabra_at_gmail.com)
Date: Sat Jan 24 2009 - 20:32:10 CST

On Wed, Jan 21, 2009 at 10:59 AM, Mahmoud A. A. Ibrahim
<m.ibrahim1982_at_yahoo.com> wrote:
> Dear AMBER
> I am writing to enquire about using amber inside Gaussian with External Keyword.
> In fact, I want to submit an ONIOM job as following:
> #p opt ONIOM(B3LYP/6-31G*:External=myscript)
> As I figured out, my script should specify the program I am going to use in my low level (MM) calculation.
> Do you have a script for amber?

No, afaik there is no such script available.

> Yes, I know I can write AMBER instead of External=myscript, but in this case I will use AMBER95 force field, as I think. So, I want to use ff99 in my MM calculations.

Actually, in ONIOM, it should be possible to specify details or the
changes in the force field, although it may not be trivial. You may
also only need to specify the changes from Amber95 to whatever version
you want to use. (I don't remember the details of ONIOM right now).

However, notice that:

1. ff99 is *not* recommended anymore. You should instead use ff99SB or ff03.
2. Unless there's a special reason to use ONIOM, I would suggest that
you also take a look into the PUPIL program to interface Amber and
Gaussian.

Cheers,
Gustavo.

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