[Pw_forum] phonon branch sorting

[Derek Stewart]

Dear Bo and Lorenzo,

I have one more suggestion on the issue of phonon branch sorting. I ran 
into this problem a while back, while working on a project on thermal 
transport in indium arsenide nanowires.  I ended up using an sorting 
algorithm that Keith Refson developed for use with phonon calculations 
in the CASTEP code.  This script works by calculating overlap matrices 
between eigenvectors at neighboring q-points.  Keith recently licensed 
this script as GPL and I have written a tool to convert the matdyn 
phonon output to the CASTEP phonon format.  For my project, I found that 
as long as you have a fairly dense mesh of q-points, it worked very well.

I am planning to put these scripts up on the web soon once I have a 
short example run to go with it.  I'll send a note to the PWSCF forum 
when it is ready.  Bo, in the meantime, I would be happy to send you the 
scripts if you are interested.

Best regards,

Derek

################################
Derek Stewart, Ph. D.
Senior Research Associate
http://sites.google.com/site/dft4nano/
250 Duffield Hall
Cornell Nanoscale Facility (CNF)
Ithaca, NY 14853
stewart (at) cnf.cornell.edu
(607) 255-2856

On 10/26/2012 8:00 AM, Lorenzo Paulatto wrote:
> On 26 October 2012 07:55, Bo Qiu <200210qb at gmail.com 
> <mailto:200210qb at gmail.com>> wrote:
>
>     Dear Dr. Paulatto,
>
>     Thanks a lot for the explanations! I'm actually writing a small
>     code to order phonon bands based on eigenvector continuities on a
>     3d grid. Thanks for pointing out there is already such option in
>     matdyn.x, I'll definitely check it out. I have finished a
>     preliminary test for my code on Al for a band crossing along
>     Gamma-K direction -- it seems to be well captured, but band
>     orderings are wrong at some random point where there is actually
>     no band crossing. I'll try to figure it out and also referring to
>     the matdyn.f90 to see what else I can do.
>     On the other hand, I think for electronic band structures one will
>     have the same problem with band ordering -- though most of time
>     people are only interested about those very few bands near Fermi
>     level. I wonder in the case of electronic band structure whether
>     continuity of wavefunction should be used to deal with band
>     ordering with band crossing? Thanks a lot!
>
>
> The bands.x code already does that, i.e. it sorts the bands using the 
> overlap of wavefunctions at consequent k-points. Again, this is an 
> option that works well for line plots, but I'm not sure it always make 
> sense to use in a 3D dispersion. Or at least, it would need to be 
> modified to sort according to neighboring points, not just according 
> to the previous point in the input list. It is not very hard to do, 
> but a bit boring as it requires a rethinking of the code structures.
>
> bests
>
> -- 
> Dr. Lorenzo Paulatto
> IdR @ IMPMC -- CNRS & Université Paris 6
> phone: +33 (0)1 44275 084 / skype: paulatz
> www: http://www-int.impmc.upmc.fr/~paulatto/ 
> <http://www-int.impmc.upmc.fr/%7Epaulatto/>
> mail:  23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05
>
>
>
>
>
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