[Pw_forum] Is maxirr=N working in phonon calculations?

[Serge Nakhmanson]

Dear All,

I run a small test with a 5-atom PbTiO3 cell in P4/mmm
symmetry, where it is supposed to have 10 irreps (i.e.,
each 3d irrep in Pm-3m symmetry splits into a 1d+2d)
and I asked the program to compute only 5 of these
as shown below:

> node02 {1003} > more PbTiO3.tp-relaxed-STO-t.ph.G.inp
> 'tp-STO-t-PbTiO3, phonons at G'
>  &inputph
>         prefix = 'tp-STO-t-PbTiO3'
>         amass(1) = 207.20000
>         amass(2) = 47.86700
>         amass(3) = 16.00000
>         tr2_ph = 1e-20
>         niter_ph = 100
>         alpha_mix = 0.5
>         maxirr = 5
>         trans = .true.
>         epsil = .true.
>         fildyn = 'PbTiO3.tp-relaxed-STO-t.G.dyn'
>         iverbosity = 1
>         outdir='./'
> /
> 0.0 0.0 0.0
> node02 {1004} > 

Still the code blasted through all 10 irreps. I grep-ped
out "maxirr" in /PH/*.f90 and saw that it is being set and reset
in multiple places (I cannot trace it without my head spinning),
so I decided to ask a question about this instead. Of course,
there is always a chance that I made a stupid error in my input,
so PLZ be kind to me :))

Also, is there any system to which irreps are computed first and
which later? Or is this process completely random, i.e. it would
be futile to cover a certain frequency window by computing only
some, but not all, irreps?

THX,

Serge


-- 
*********************************************************
  Serge M. Nakhmanson               phone: (630) 252-5205
  Assistant Scientist                 fax: (630) 252-4798
  MSD-212, Rm. C-224
  Argonne National Laboratory
  9700 S. Cass Ave.
  Argonne, IL 60439
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