<html><head></head><body><div style="font-family:verdana, helvetica, sans-serif;font-size:13px;"><div><div>Dear all,<br></div><div><br></div><div>Please how do you get rid of a
negative phonon frequency at a Gamma point. I have done some trial calculations
for two different 2D materials. Please find the results details below:</div><div><br></div><div>System 1:</div><div><br></div><div>ph.x results at Gamma point</div><div><br></div><div> q = ( 0.000000000 0.000000000 0.000000000 ) <br><br> **************************************************************************<br> freq ( 1) = -0.716980 [THz] = -23.915891 [cm-1]<br> freq ( 2) = 1.170257 [THz] = 39.035571 [cm-1]<br> freq ( 3) = 2.301718 [THz] = 76.777040 [cm-1]<br> freq ( 4) = 4.692676 [THz] = 156.530836 [cm-1]<br> freq ( 5) = 6.547729 [THz] = 218.408714 [cm-1]<br> freq ( 6) = 7.575469 [THz] = 252.690440 [cm-1]<br> freq ( 7) = 7.954771 [THz] = 265.342590 [cm-1]</div><div><br></div><div><br></div><div>matdyn.x results</div><div><br></div><div>diagonalizing the dynamical matrix ...<br><br> q = 0.0000 0.0000 0.0000<br> **************************************************************************<br> freq ( 1) = -0.168246 [THz] = -5.612090 [cm-1]<br> ( -0.205675 0.000000 -0.162406 0.000000 -0.049537 0.000000 )<br> ( -0.204095 0.000000 -0.166786 0.000000 -0.047497 0.000000 )<br> ( -0.202604 0.000000 -0.168584 0.000000 -0.038435 0.000000 )<br> ( -0.204187 0.000000 -0.166901 0.000000 -0.037977 0.000000 )<br> ( -0.204822 0.000000 -0.164879 0.000000 -0.035645 0.000000 )<br> ( -0.204067 0.000000 -0.159939 0.000000 -0.043878 0.000000 )<br></div><div><br></div><div><br></div><div><br></div><div>System 2:</div><div><br></div><div>ph.x results at Gamma point</div><div><br></div><div> q = ( 0.000000000 0.000000000 0.000000000 ) <br><br> **************************************************************************<br> omega( 1) = -2.676536 [THz] = -89.279630 [cm-1]<br> omega( 2) = 2.176387 [THz] = 72.596456 [cm-1]<br> omega( 3) = 2.268904 [THz] = 75.682505 [cm-1]<br> omega( 4) = 2.781243 [THz] = 92.772280 [cm-1]<br> omega( 5) = 2.831070 [THz] = 94.434329 [cm-1]<br> omega( 6) = 5.362633 [THz] = 178.878184 [cm-1]<br> omega( 7) = 5.391573 [THz] = 179.843530 [cm-1]</div><div><br></div><div><br></div><div>matdyn.x results </div><div><br></div><div>diagonalizing the dynamical matrix ...<br><br> q = 0.0000 0.0000 0.0000<br> **************************************************************************<br> omega( 1) = -0.081634 [THz] = -2.723002 [cm-1]<br> ( -0.270214 0.000000 -0.101393 0.000000 -0.001203 0.000000 )<br> ( -0.270014 0.000000 -0.100654 0.000000 0.001122 0.000000 )<br> ( -0.270492 0.000000 -0.099822 0.000000 0.003548 0.000000 )<br> ( -0.270726 0.000000 -0.100219 0.000000 0.003104 0.000000 )<br> ( -0.271070 0.000000 -0.100621 0.000000 0.006056 0.000000 )<br> ( -0.270797 0.000000 -0.101038 0.000000 0.002118 0.000000 )<br> ( -0.270725 0.000000 -0.100220 0.000000 -0.002122 0.000000 )<br></div><div><br></div><div><br></div><div>Lastly,
do you think the results above will affect Tc calculations. If Yes,
please advice me on what to do to remove the negative frequencies in
both cases.</div><div><br></div>Yusuf Zuntu</div><div>PhD candidate</div><div>School of Physics</div><div>USM, Maalysia<br></div><div><br></div><div><br></div><div><br></div><div><br></div></div></body></html>