[Pw_forum] Separation between acoustic modes and optical modes

[Derek Stewart]

Hi Umesh,

If you are interested in sorting overlapping phonon branches so that you can plot them, then you need to sort them at each q point based on the phonon eigenvector like Stefano noted.  You can find this in the output from the matdyn calculation.

Keith Refson developed a script to sort phonon branches and plot them correctly based on eigenvectors for DFPT phonon calculations using CASTEP.  Overrall, it does a very good job.  I wrote a small script that converts the QE output to the CASTEP format.  If you are interested, I can send you a copy of the codes.

Best regards,

Derek

Derek Stewart
Principal Research Scientist
HGST, A Western Digital Company
derek.stewart at hgst.com<mailto:derek.stewart at hgst.com>
Office: (408) 717-5901
[HGST_aWDco_closing_sm_wLLD]
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From: pw_forum-bounces at pwscf.org [mailto:pw_forum-bounces at pwscf.org] On Behalf Of Umesh Roy
Sent: Saturday, August 1, 2015 4:22 AM
To: pw_forum at pwscf.org
Subject: [Pw_forum] Separation between acoustic modes and optical modes

Dear All,
           I have calculated modes of vibration of Iron in different directions for a fix phonon wave vector q (in a large number of directions). Since in Quantum espresso phonon modes are printed in increasing order for a given q vector. For a small group of q the acoustic and optical branches do not overlap so, we can easily separate out the acoustic branch from the optical branch. As we increase the magnitude of q the acoustic branch and the optical branch get mixed up. So , how to separate out the acoustic modes or is there any way of filtering the optical modes?


Thank you in advance


Umesh Chandra Roy
Research Scholar, School of Physical Sciences
Jawaharlal Nehru University, New Delhi-110067,
India.
Email:umesh24crp at gmail.com<mailto:Email%3Aumesh24crp at gmail.com>
Mobile:+919868022722
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