[Pw_forum] questions on the acoustic sum rule crystal

[Eduardo Ariel Menendez Proupin]

Hi,

Question 1. This question is about the Acoustic Sum Rule in phonon
calculations. Is there a reference to learn about the option zasr='crystal'?

Is 'crystal' always better than 'simple' ?

  !     zasr       :  Indicates type of Acoustic Sum Rules used for the Born
  !                   effective charges (character):
  !                   - 'no': no Acoustic Sum Rules imposed (default)
  !                   - 'simple':  previous implementation of the asr used
  !                     (3 translational asr imposed by correction of
  !                     the diagonal elements of the force-constants matrix)
  !                   - 'crystal': 3 translational asr imposed by optimized
  !                      correction of the IFC (projection).

Question 2. Consider the calculation of the phonon DOS, as in example 06.
The ASR can be imposed in the run of q2r and/or in the run of matdyn, let's
say
There are four combinations of zasr-asr in q2r an matdyn
        q2r          matdyn
 1       no         no
 2       no         crystal
 3      crystal    no
 4      crystal    crystal

Should  there be  differences in the final DOS in the combinations 2, 3, and
4?

-- 
Eduardo Menendez
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