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

Paul Jefferson jefferph at xsmail.com
Thu Feb 24 08:02:42 CST 2005


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.
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