Siesta

number of supercells in vibra.h

Asked by Tony

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.

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Tony (tony2017) said : 		#2

Hi Nick,
This suggestion works, but I have to reduce the number of atoms.
With:
      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)?

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Nick Papior (nickpapior) said : 		#3

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