Subject: Summary : Dipole-Dipole Interaction in D

From: "MSBEA01.SUBRAPS" <[email-masked]>
Date: 26 Feb 1996 12:19:12 GMT

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Dear CCL members,

  A while ago I posted a query on dipole-dipole interactions , the following
is a summary of responses that I received.

Thanking you all for your time

 --Mani--

Dr. P. S. Subramanian
Fuels and Lubrication Division
Texaco Inc.
P. O. Box 509
Beacon, NY 12508
email: [email-masked]
vmail: 914-838-7561

Response 1.

You have a very strange header above your mail. It sounds almost as if
you expect your mail to be tainted by the filth of the transport through
internet :-)
What does it mean?

It was this text that aroused my curiosity, i don't know of any MD packages
that do dipole-dipole interaction. Maybe Gromos does it, it seems to be
quite advanced.

Greetings,
Frits Daalmans

Frits Daalmans
OIO Conformational Analysis
Gorlaeus Laboratoria
Leiden, The Netherlands
E-mail: [email-masked]
Tel: [+31] (0)71-5274505

Response 2.

Dear Dr. P. S. Subramanian

Could you summarize responses for your querry on CCL ?
Grzegorz Bakalarski
ICM Warsaw University

Response 3.

Hi Mani,

To my knowledge only MM3 incorporates such a entity. It uses bond dipoles
for such a purpose. Everyone else uses point charges (monopole
approximation)
to reproduce these properties.

If you have a good reason to need the electrostatics (which is probably
why you asked the net...) and cannot use a bond dipole scheme, then I
would strongly suggest that you perform ab initio calculations, say at
the HF/6-31G(d,p) level (or 6-31+G(d,p) if you have anions) and compute
the monopole charges from a fit of the electrostatic potential. This
method reproduces the molecular dipole moment pretty well; I'm not so
sure about the molecular quadrupole moment, though. Use of Mulliken and
Natural Bond Order methods is not recommended for this purpose. Be
sure that you use a large enough basis set to suitably reproduce the
electron density of the systems you are interested in.

(As an aside, I stumbled upon this many years ago in grad school by trying
to
use Mulliken-based charges to reproduce the dipole moments in simple
lipids. I failed miserably. In my thinking during that time, I was sure
that I could reproduce the molecular dipole from point charges--after
all, we all learned it could be done in our fields courses. But of course
I was not aware that Mulliken population analysis was not based on
trying to reproduce the molecular dipole. It took me a while to realize
that it was the method, not the idea, that was at fault.)

Hope this helps,

Craig

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Response 4.

Any package that does molecular dynamics with an MM2-derived force field
should include interactions of bond dipoles.  (HyperChem does; please
contact me for details.)  I don't know of any that explicitly include
effects of molecular dipoles, but I'm not sure if that's what you were
asking about.

Joel

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Joel Polowin, Ph.D.   Manager, Scientific Support
Email to: [email-masked]

Hypercube Inc, 419 Phillip St, Waterloo, Ont, Canada N2L 3X2 (519)725-4040
Info requests to: [email-masked]    Support questions to: [email-masked]
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Response 5

Orient 3.2 by Anthony Stone of Cambridge University calculates all sorts of
things using electrostatic expansions i.e., charges, dipoles, quadrupoles
etc.  The new version has basic molecular dynamics in it.  If you want a
copy you'll have to Email him directly on [email-masked] and explain who
you are and why you want to use it.

Darren Andrews.

University of Manchester,
Department of Chemistry,
Oxford road,
Manchester.
M13 9PL.

[email-masked]
PGP: 512/A971A9

Tel: 0161 275  4699.
Fax: 0161 275 4598.