[Pw_forum] The coordinate of X-point in GaAs band structure calculation

[Andrew Supka]

Evan,

Specifying the k points to form a path between high symmetry points for the
band structure plots is supported when ibrav != 0. I Can't remember exactly
what version this was added but I can verify that it's in QE 5.3+. By
default when using this style of k_points input this convention is followed:
https://arxiv.org/abs/1004.2974

For example..

K_POINTS {crystal_b}
5
gG 8
X 8
R 8
M 0

I'm not sure if K,W, or L is supported in this style of input for ibrav=1.
With Ibrav=2 (fcc) I know they are supported for this style.

The coordinate of X in reciprocal space depends on how you define your
reciprocal lattice vectors. Using ibrav!=0 defines the reciprocal lattice
vectors which are listed in the pw.x input documentation.

Also I noticed in your input you have occupations="tetrahedra". From the
pw.x documentation..

"especially suited for calculation of DOS
(see P.E. Bloechl, PRB 49, 16223 (1994)).
Requires uniform grid of k-points,
automatically generated (see below).
Not suitable (because not variational) for
force/optimization/dynamics calculations."

The path between high symmetry points is not a grid. I'm not sure what
effect using occupations="tetrahedra" would have on k points in a path but
I'm not sure if it's appropriate for a band structure calculation.

Regards,

Andrew Supka
Ph.D Student
Science of Adv. Materials Program
Central Michigan University

On Oct 29, 2016 10:03 AM, "evan" <ewan26 at 126.com> wrote:

> Hello, everyone
>
> I calculated the band structure of GaAs in a simple cubic lattice cell
> (ibrav=1), I searched from the internet the coordinates of X-point in the
> first Brillouin zone are 2pi/a(0,0,1) or 2pi/a(1,0,0), but both results
> show that band gap occurs at G and X points simultaneously, it seems to me
> that the X is equivalent to G, can you tell me the correct X point
> coordinates which give me the reasonable result. The input files and
> results are attached, you can show what is wrong in the input file.
>
> Your suggestions are appreciated.
>
> Yours sincerely
>
> Evan
>
> USC, China
>
>
>
>
>
>
>
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