AMBER Archive (2008)

Subject: Re: AMBER: Fully QM periodic runs

From: David A. Case (
Date: Tue Nov 25 2008 - 05:56:51 CST

On Mon, Nov 24, 2008, wrote:
> We've recently become interested in performing periodic QM/MM calculations
> in Amber, but with a purely QM system.

No, Amber is no where close to being able to support this capability. I think
Ross' earlier explanation says it well:

> Unfortunately in Amber 9 [or 10!] one cannot do a pure QM periodic
> system. You can only do QM/MM with periodic boundaries and this has the
> restriction that the QM region dimension + cutoff must not extend beyond the
> box boundaries. I.e. it is designed for modelling say an active site in a
> protein that is then solvated.

Basically, there are only Coulomb interactions (and no exchange interactions)
computed between quantum regions in different unit cells. And, there is no
notion of k-space at all. We are simply attacking a very different problem
than the one you describe.

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