[Pw_forum] 110-direction Vs 110-point calculation

[GAO Zhe]

Dear S. Chab:
Definitely, I am not clear about your system.
Which is the 4x4x4 M-P mesh? for k-points or q-points? If it is for k-points, then I think it is too small. But any way, I think the convergence test and well relaxation should be done before phonon calculation.
For the [110] direction, which means the path from Gamma to X, in your system. X is just a point in FBZ and corresponds to (110) or (1/2, 1/2, 0) based on different cells. Of course, you can directly calculate frequencies by specifying a series of q-points along [110] direction in ph.x. But, running the whole phonon dispersion at converged q-mesh and only draw Gamma->X out is better choice.


--
GAO Zhe
CMC Lab, Materials Science & Engineering Department,
Seoul National University, South Korea
 

At 2012-08-14 21:18:39,"Satyananda Chab" <csatya11 at gmail.com> wrote:





Dear Users,
I am trying to calculate the full phonon spectrum of a ferromagnetic alloy but the results that I found are not matching with literature. So I want to know 


(1) How to assign 110-direction for a grid calculation? 


(2)Whether calculating phonon spectrum from Gamma to X point along 110 direction is the same as that of a single point calculation at 110 point for this


particular point.

(3)Will both calculations give the same frequencies at 110 point?

(4)My phonon spectrum do not match previous papers. Is there anything to do with grid size?(I used 4X4X4 Monkhorst pack )

If anybody throw me some light on these questions, i will be very happy.

Thanking you in advance

SATYANAND  CH
Junior Research Fellow
Department of Physics
Gauhati University
Guwahati 781014
(+91)950-895-6853
email: csatya11 at gmail.com




me as that of a single point calculation at 110 point.

(3)Will both calculations give the same frequencies at 110 point?

(4)My phonon spectrum do not match previous papers. Is there anything to do with grid size?(I used 4X4X4 Monkhorst pack )

If anybody of you throw me some light, i will be very happy.

Thanking you in advance

SATYA NANDA  CH
Junior Research Fellow
Department of Physics
Gauhati University
Guwahati 781014
(+91)950-895-6853
email: csatya11 at gmail.com
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