[MMTK] principal axes

[Jochen Küpper]

I need to put GroupOfAtoms (GA) into their principal axis system (PAS)
and am looking for some comments on my ideas:

As I see it I have move all atoms of the GA to new positions so the
implicit axis system is the PAS. As MMTK doesn't provide a method to
do that directly, I am thinking of the following algorithm: 

- get COM and inertial tensor of GA (MMTK), diagonalize tensor (NumPy)
- get atomList() of GA (MMTK)
- translate and rotate every atom to its PAS position 
- setPosition() for atoms (MMTK) 
voila, there's a modified GA with the internal axis system
corresponding to the PAS.

Is this usage of atomList() + setPosition() ok? Are there any obvious
problems I am overseeing?

Greetings,
Jochen
-- 
Einigkeit und Recht und Freiheit                http://www.Jochen-Kuepper.de
    Liberté, Égalité, Fraternité                GnuPG key: 44BCCD8E
        Sex, drugs and rock-n-roll