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<DIV><FONT size=2 face=宋体><SPAN lang=EN-US><FONT size=3 face=Calibri>Dear
all</FONT></SPAN></DIV>
<DIV>
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size=3 face=Calibri> </FONT></o:p></SPAN></P>
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<P style="MARGIN: 0cm 0cm 0pt" class=MsoNormal><SPAN lang=EN-US><FONT size=3
face=Calibri>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. <SPAN
style="mso-spacerun: yes"> </SPAN>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. </FONT></SPAN></P>
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size=3 face=Calibri> </FONT></o:p></SPAN></P>
<P style="MARGIN: 0cm 0cm 0pt" class=MsoNormal><SPAN lang=EN-US><FONT size=3
face=Calibri>Thanks and best regards</FONT></SPAN></P>
<P style="MARGIN: 0cm 0cm 0pt" class=MsoNormal><SPAN lang=EN-US><o:p><FONT
size=3 face=Calibri> </FONT></o:p></SPAN></P>
<P style="MARGIN: 0cm 0cm 0pt" class=MsoNormal><SPAN lang=EN-US><FONT size=3
face=Calibri>Wei-Bing Zhang</FONT></SPAN></P>
<P style="MARGIN: 0cm 0cm 0pt" class=MsoNormal><SPAN lang=EN-US><FONT size=3
face=Calibri></FONT></SPAN> </P></FONT></DIV>
<DIV><FONT size=2
face=宋体>----------------------------------------------------------------------<BR>Dr.
Wei-Bing Zhang</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2 face=宋体>School of Physics and Electronic Sciences<BR>Changsha
University of Science and Technology,<BR>Changsha, People’s Republic of
China<BR>Phone : +86 186 73108538<BR>E-mail: <A
href="mailto:zwb256@hotmail.com">zwb256@hotmail.com</A>, <A
title="mailto:weibingzhangavh@gmail.com
CTRL + 单击以下链接"
href="mailto:weibingzhangavh@gmail.com">weibingzhangavh@gmail.com</A><BR>----------------------------------------------------------------------</FONT></DIV></BODY></HTML>