The most important thing to include is the use of a propagation vector or better still, several. This means that a general magnetic structure can be built up by adding contributions from different fourier components that are defined within the nuclear cell. The matrix relating nuclear and magnetic cells is then irrelevant and the source of lots of confusion will be removed.
Then I would suggest the ability to define the moments in a number of ways:
1) the chi and phi angles
2) components with respect to the space group axes (symmetry can be easier to read in the natural coordinate system of the problem!)
3) as complex basis vectors (again, this is the most general form of a fourier component and means that *all* types of structure can be drawn)
For ease, it is probably reasonable to expect that the moments will be defined for all of the equivalent positions within the nuclear cell and those related by centring translations. This also means that you can avoid Shubnikov space groups if you want to...
Best regards,
Andrew
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Dr. Andrew S. Wills,
Dept. of Chemistry,
Christopher Ingold Laboratories,
University College London,
20 Gordon Street,
London,
WC1H 0AJ,
UK.
On 26 Jul 2004, at 23:03, Larry W. Finger wrote:
Martin Kroeker and I have been asked to add an option to our crystal structure drawing program DRAWxtl that would represent magnetic spin vectors with an arrow. Because I don't really understand magnetic space groups, I would rather not implement a full-blown space-group generator. Would the following parameters be useful in describing the position and orientation of such spins?
1. fractional coordinates of nucleus in nuclear unit cell.
2. angles from vector to z and x axes - essentially chi and phi
3 3 x 3 matrix relating magnetic unit cell to the nuclear one
If there are a better set of parameters, I would appreciate learning of them.
Thanks,
Larry Finger
