Subject: Re: CCL:helix dipole

From: [email-masked] (Eberhard von Kitzing)
Date: Mon, 25 Apr 94 13:08:26 +0200

>In his mail Rafael Najmanovich says :
>>
>>         For each pair of opposite charges in the helix you have a dipole
>> momentum vector that points from the positive to the negative charge so I
>> suppose the total dipole momenta vector of that helix will be the
>> vectorial sum of all these vectors. How to calculate it in practice (that
>> is, if there are approximation methods or computer algorhitms) I don't know.
>>
>
>   I beg to differ. I would rather -
> (a) Find the center of mass of all the positive charges.
> (b) Find the center of mass of all the negative charges.
> (c) Find the dipole moment between these two points.

As long as the helix is electrically neutral both results should agree!

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Eberhard von Kitzing
Max-Planck-Institut fuer Medizische Forschung
Jahnstr. 29, D69120 Heidelberg, FRG

Carl-Zuckmayer Str. 17, D69126 Heidelberg (privat)

FAX : +49-6221-486 459  (work)
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internet: [email-masked]

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From: "G. Ravishanker" <[email-masked]>
Date: Mon, 25 Apr 1994 08:48:52 -0400

Hi

If you have a set of charges qi, on atomic centers (xi,yi,zi), for
i=1,natom, isn't it simpler to transform the coordinates to the principal
axis system and do:

   	dx = sum over all atoms qi*xi
   	dy = sum over all atoms qi*yi
   	dz = sum over all atoms qi*zi

   	D = sqrt(dx**2 + dy**2 + dz**2)

Ravi

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