[Wannier] degenerate bands in group velocity

[nafise rezaei]

Dear Jonathan,

I read your "Spectral and Fermi surface properties from Wannier
interpolation" paper.
but I do not know exactly, what should I do at the degenerate
states.?elements off-diagonal HH_alpha(k) matrix are zero at the
non-degenerate band.Would you please you explain about elements of
this matrix at the degenerate states? HH_alpha(k) matrix is sum of two
term: HHbar_alpha(k) term and multiplication of HH(k) and
DH_alpha(k).

at the degenerate states second term is zero. Are elements of first
matrix (HHbar_alpha(k)) for m/=n zero?
I wrote program for calculation of group velocity.at  the degenerate
states elements of HHbar_alpha(k) are zero for (m/=n) and non-zero for
(m=n) . is this true?


I appreciate your help.
yours
  Nafise