From owner-chemistry.,at,.ccl.net Thu May 18 21:34:01 2006
From: "Guilherme Menegon Arantes garantes * iq.usp.br" <owner-chemistry.:.server.ccl.net>
To: CCL
Subject: CCL: QM/MM computational cost?
Message-Id: <-31785-060518160314-29203-GNMRUcyRUaIRAk0WnAy9kw.:.server.ccl.net>
X-Original-From: Guilherme Menegon Arantes <garantes..:..iq.usp.br>
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Date: Thu, 18 May 2006 16:10:41 -0300
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Sent to CCL by: Guilherme Menegon Arantes [garantes],[iq.usp.br]
On Thu, May 18, 2006 at 01:21:47PM -0400, Ross Walker ross]|[rosswalker.co.uk wrote:
> Sent to CCL by: "Ross Walker" [ross|*|rosswalker.co.uk]
> 
> [.....]
> before it even starts to become expensive. Plus you can do a simulation with
> a full treatment of electrostatics and periodic boundaries for both the QM
> and MM regions using PME. Without a PME treatment you will need to use an
> infinite (i.e. no) cutoff and probably add an implicit solvent treatment for
> the gas phase region of your system to get meaningful results. Using a cut
> off with gas phase / water cap simulations introduces serious artefacts into
> your simulation and can completely invalidate your results. Hence often it
> can be quicker to do a full PME treatment than to run the gas phase
> non-periodic simulation.
> [.....]


I would appreciate if you could point me to any references showing this
explicitely. 

In my experience, properties (say, PMF) calculated in QM/MM simulations 
with some truncation schemes, in particularly atom-based force-switching,
with reasonable cut-off radius, are equivalent to the properties 
obtained without any truncation.

G

______________________________________________________

Dr. Guilherme Menegon Arantes        Sao Paulo, Brasil
______________________________________________________

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