[Pw_forum] A strange problem in phonon calculation

[Wei-Bing Zhang]

Dear all
 


Recently, I am trying to calculate the phonon dispersion of 2D materials. I used 4x4x1 q-points in phonon calculation whereas a 16x16x1 k-points for self-consistent electronic calculation. The direct calculations indicate that all phonons frequencies are above zero on the grid of q-vectors including the Gamma point. However, when I transformed the dynamical matrices from G- to R-space and calculated phonon dispersions using “matdyn.x”, some negative frequencies appear in acoustic mode ZA near Gamma point.  Since I am really a new user for phonon calculation, I am not sure what happened. The input and output file are enclosed. Could you tell me what’s wrong with my calculations? Any suggestions will be appreciated. 

 

Thanks and best regards

 

Wei-Bing Zhang



----------------------------------------------------------------------
Dr. Wei-Bing Zhang

School of Physics and Electronic Sciences
Changsha University of Science and Technology,
Changsha, People’s Republic of China
Phone : +86 186 73108538
E-mail: zwb256 at hotmail.com, weibingzhangavh at gmail.com
----------------------------------------------------------------------
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20130618/0a05c0b3/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: test2.tar.gz
Type: application/octet-stream
Size: 69544 bytes
Desc: not available
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20130618/0a05c0b3/attachment.obj>