[SciPy-user] Eigenvalues for bandstructures problem...

[Paul Jefferson]

Hi,

I have been using the linalg module in scipy (as well as the 
LinearAlgebra module in Numeric, and the Linear_Algebra module in 
numarray) to calculate the eigenvalues of a 4x4 hamiltonian matrix that 
calculates semiconductor bandstructures. A variable k is cycled through 
changing the elements of the matrix and the eigenvalues are obtained 
for each value of k. Each band is defined by one eigenvalue (0,1,2 or 3 
in the returned array) for all k. On plotting the bands as a function 
of k. I noticed that the eigenvalues swap over at certain values of 
(+/-) k (best seen in the attached figure). I was wondering if anybody 
knew of this problem using the linalg package? (I don't have the same 
problem with octave (which I think also uses atlas)).

If anyone can throw any light on this problem it would be much 
appreciated.

Best Regards,

Paul Jefferson.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: bands.pdf
Type: application/pdf
Size: 29443 bytes
Desc: not available
URL: <http://mail.scipy.org/pipermail/scipy-user/attachments/20050224/01b0157e/attachment.pdf>