[Pw_forum] problem for generating q-points using kpoint.x

[Aaron Jung]

Dear all users,

Hello.

I calculate for superconducting parameters using QE+EPW,
My system is body-centered tetragonal structure(No. 139, ibrav=7).

I have two question, but same problem.

First,
in ph.x process, the 4 q-points are shown for 2x2x2 q-mesh.
For lambda.x calculation, when I got an weight value using kpoint.x,
the meshes are different with the q-points in ph.out file.

Q) what is fifth number in the generated file? For example, 3 in 4th low or
2 in 7th low?
Q) How can I match the q-points in ph.out and generted out file?

===================================================
In ph.out file.

     Dynamical matrices for ( 2, 2, 2)  uniform grid of q-points
     (   4q-points):
       N         xq(1)         xq(2)         xq(3)
       1   0.000000000   0.000000000   0.000000000
       2   0.500000000   0.000000000  -0.146200241
       3   0.500000000  -0.500000000  -0.292400482
       4   0.000000000   0.000000000  -0.292400482

In generated out file from kpoints.x
    8
    1   0.0000000  0.0000000  0.0000000   1.00
    2   0.5000000 -0.5000000  0.0000000   2.00
    3   0.0000000  0.5000000  0.1462002   4.00
    4   0.5000000  0.0000000  0.1462002   0.00   3
    5  -0.5000000  0.0000000  0.1462002   0.00   3
    6   0.0000000 -0.5000000  0.1462002   0.00   3
    7  -0.5000000  0.5000000  0.2924005   0.00   2
    8   0.0000000  0.0000000  0.2924005   1.00
=====================================================


Second,
In EPW calculation, there are 5 process.

for getting a phonon dispersion
1. pw.x <scf.in> scf.out
2. ph.x <ph.in> ph.out

for epw process
3. pw.x <scf.in> scf.out
4. pw.x <nscf.in> nscf.out
5. epw.x <epw.in> epw.out

In the nscf calculation, I need the nscf klist consistent with elph k-point
grids.
2x2x2 q-points need 8 nscf klist(satisfying with positive k-points in 1BZ).
I used the generated klist from kpoins.x, however this klist should be
positive value.

    8
       0.0000000  0.0000000  0.0000000
       0.5000000  0.5000000  0.0000000
       0.0000000  0.5000000  0.1462002
       0.5000000  0.0000000  0.1462002
       0.5000000  0.0000000  0.1462002
       0.0000000  0.5000000  0.1462002
       0.5000000  0.5000000  0.2924005
       0.0000000  0.0000000  0.2924005

But, 3th and 6th low are same point. 4th and 5th also are same.
So, I need other two values.

Q ) Any good idea?

Also, could you suggest any literature or reference?



Thank you,
Myung-Chul.


===========================================

Myung-Chul Jung


Ph. D student

Department of Applied Physics

Korea University, Sejong campus

2511 Sejong-ro, Sejong

30019, Republic of Korea

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