Dear all:

I am playing with the examples for LDA+U. I think that understand that the 
eigenvalues and eigenvectors refer to the occupation matrix, which is 
calculated from the projections onto the proper states of the atom for which U 
correction is to be applied. However, there are two issues which are confusing 
to me:

1) If I diagonalize occupation matrix externally to QE, I do get the same 
eigenvalues, but quite different eigenvectors, beyond numerical errors, I 
think. Could anybody explain to my why does this happen?

2) Suppose that I need to use the ?starting_ns_eigenvalue? option to correct 
unreallistic occupations. For that, I have a look at the eigenvalues of the 
occupation matrix at convergence. However, since the occupation matrix changes 
during the calculation (because the d states, say, may mix together), the 
eigenvectors also do. It means that, despite I may know which occupation is 
unphysical at convergence, I cannot know what was the corresponding eigenvalue 
at the first iteration. Am I right? If so, how can I apply 
?starting_ns_eigenvalue? correctly?

Thanks in advance.

Juanjo

Juan J. Mel?ndez 
Associate Professor
Department of Physics ? University of Extremadura
Avda. de Elvas, s/n 06006 Badajoz (Spain)
Phone: +34 924 28 96 55
Fax: +34 924 28 96 51
Email: melendez at unex.es
Web: http://materiales.unex.es/miembros/personal/jj-melendez/Index.html

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