[Pw_forum] Bands calculation for Silica

Francesco Pelizza francesco.pelizza at strath.ac.uk
Mon Dec 8 13:26:23 CET 2014

Extremely Cheers Paolo !!

I wish you a wonderful day !!



On 08/12/14 08:39, Paolo Giannozzi wrote:
> On Fri, 2014-12-05 at 16:48 +0000, Francesco Pelizza wrote:
>> - in the bands plot some strange "crossover" (errant behaviour) appear
>> and i do not know what it means.
> it means that the algorithm that tries to align bands doesn't work well.
> If you just plot bands as they come out of the calculation, they will
> be ordered from lowest to highest state and you will miss the correct
> crossings. The code tries to align energies along the true bands using
> one of the following two methods (see the documentation of bands.x):
> - by maximising band overlap between adjacent k-points
> - by finding band irreps (irreducible representations)
> The first one often fails, the second is clumsy.
> Please also note that the highest bands in a non-scf calculation may
> sometimes not be the real ones, due to the way iterative diagonalization
> works. In a non-scf calculation you should compute a few more bands than
> those you plan to use or plot.
> Paolo

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