[Pw_forum] error in during bands.x

Paolo Giannozzi giannozz at nest.sns.it
Mon Feb 28 10:55:45 CET 2005

On Sunday 27 February 2005 22:45, Eyvaz Isaev wrote:

> --- Sergey Lisenkov <proffess at yandex.ru> wrote:
> > I looked at sources and found that maxdeg=4 (max
> > allowed degeneracy). I am interested what is the
> > value I should use?
> Perhaps you have eigenvalues with more than 4-fold
> degeneration. Try maxdeg>4, say maxdeg=10 (just as an
> example, to be more precise, you have to look at your
> bands file), recompile the program and try again.

the algorithm assumes that all states whose energies are 
closer than eps, presently set to 0.001 Ry, are degenerate.
This information is used to deal with band crossing at high
symmetry points. Accidental degeneracies can occur, though.
I think that maxdeg can be safely increased, even if group
theory says the opposite. Alternatively, eps can be reduced
to prevent accidental degeneracies.


Paolo Giannozzi             e-mail:  giannozz at nest.sns.it
Scuola Normale Superiore    Phone:   +39/050-509876, Fax:-563513 
Piazza dei Cavalieri 7      I-56126 Pisa, Italy

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