[Pw_forum] How to correctly use Wyckoff potition and crystal_sg

[Paolo Giannozzi]

In the calculation of projected DOS, symmetry is used to perform the
average  over k-points (only k-points in the irreducible Brillouin
Zone are available). One might instead sum over all k-point, use
symmtery to compute only inequivalent atoms. You cannot do both at the
same time.

Pa;p

On Sun, Apr 9, 2017 at 6:42 AM, balabi <balabi at qq.com> wrote:
> Thank you so much, Paolo!
> I now know how to use crystal_sg. But I just realized that to specify
> crystal structure in 'crystal_sg' is actually equivalent to 'crystal'.
> Because inside PW, they both processed to same thing by dist.x.
> However, I don't understand why the output of PDOS or KPDOS contains
> multiple of inequivalent atoms? For example, silicon has two atoms in a
> primitive cell. If we want to use 'crystal' we have to specify two atoms.
> While if we want to use 'crystal_sg', we only need to specify one atom,
> because the two silicon atoms is equivalent in a primitive cell. But the
> PDOS output contains both atoms although the content is the same. At first,
> I thought if I specify 'crystal_sg', I could output only inequivalent PDOS
> files. However, I am wrong.
> So my question is why QE outputs duplicated PDOS file for equivalent atoms?
>
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222