AMBER Archive (2007)

Subject: Re: AMBER: Pi-pi interactions

From: Adrian Roitberg (roitberg_at_qtp.ufl.edu)
Date: Mon May 21 2007 - 08:56:51 CDT

A pseudo philosophical point needs to be made, regarding Dave's comment.

EVERY interaction term between atoms is a quantum effect !
This applies to vdw, electrostatics, bonds and angles, etc.

So, the issue is not quantum versus force fields, but 'are force fields
able to reproduce real (quantum) data'.
As Jiri pointed out, for base-base stacking his group has checked this
very thoroughly, and it works great.

Cheers
a.

Jiri Sponer wrote:
> Aromatic base stacking (with neutral stacking systems) is one of the
> best approximated contributions in amber, deviations from
> full quantum surfaces (MP2 as well as recently complete basis set
> MP2 + noniterative triple excitations corrections) are minimal and
> do not indicate presence of any specific pi-pi terms.
>
> Best wishes, Jiri
>
>
>> No, there are no pi-pi interactions in any of the AMBER forcefields. This
>> is a quantum effect, and is not treated in any classical forcefield.
>> Emulation of this effect can come about only via favorable van-der Waals
>> interactions, and hopefully the physics is not upset by the qq/r
>> point charge interactions.
>>
>> Dave
>>
>>
>> On Mon, 21 May 2007, Roberto Veiga wrote:
>>
>>> Dear all:
>>>
>>> are the Amber force fields suitable to this kind of interaction (pi-pi)?
>>>
>>> []s,
>>>
>>> Roberto
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-- 
                            Dr. Adrian E. Roitberg
                              Associate Professor
               Quantum Theory Project and Department of Chemistry

University of Florida                         PHONE 352 392-6972
P.O. Box 118435                               FAX   352 392-8722
Gainesville, FL 32611-8435                    Email adrian_at_qtp.ufl.edu
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