[Phonopy-users] Issue with plotting and cell definition

[eric h. <er...@vi...>]

Hi everyone,

I am having issues plotting the dispersion for FCC Al while using phonopy
as a python module. The current examples are just a simple 1x1x1 cell, as I
am just trying to get the code setup, and the small cell if a quick
calculation.  I am using phonopy with quantum espresso, and have run the
simulation through the command interface (as described in the tutorials).
This gives the expected three acoustic modes of a single atom basis with an
FCC lattice (disperion.png).

I have then started to create a python script so that I have more control
over output.  When I run this code it does not appear to use the primitive
cell like in the case of the command prompt.  This is apparent by the
folding of the acoustic bands over the "reduced" brillouin zone, giving
rise to what appears like optical modes (Figure_2).

My question is: What am I missing in my python code (that the command line
is executing) to result in the correct dispersion defined by the primitive
cell? I have attached my python script below with commented cells.

Any help would be greatly appreciated!
Thank you,
Eric Hoglund
University of Virginia