number of supercells in vibra.h

Asked by Tony on 2017-04-10

Dear all,

Does anyone know how to increase number of supercells in phonon calculation (fcbuild and vibra), for instance up to 10 in each direction?

I have found a topic discussed about this problem: https://<email address hidden>/msg07954.html

But what Nick suggested there is just increasing the total number of atoms, not number of supercells. I have tried but maximum number I can increase is upto 5 in each direction by set up (in the vibra.h file):
      parameter (maxx = 5)
      parameter (maxy = 5)
      parameter (maxz = 5)

For larger numbers, it made error "siesta make: *** [vibra] Error 1" for compiling the executable vibra.

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Nick Papior (nickpapior) said : #1

Try and decrease the number of atoms and increase the number of supercells.
1) set maxa to the number of atoms before running fc-build
2) set supercells to the number of supercells you use

If this still errors out please let us know.

Tony (tony2017) said : #2

Hi Nick,
This suggestion works, but I have to reduce the number of atoms.
      parameter (maxx = 10)
      parameter (maxy = 10)
      parameter (maxz = 10)
If I set maxa = 40, it still shows error. However, if I set maxa = 38, it works.

I guess there is a fixed value for (number of atoms)*(number of supercells)?

Nick Papior (nickpapior) said : #3

The fixed value is compiler and system dependent due to the linker.