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Dear all,<div><br></div><div>I am doing some phonon calculations at the gamma point for a system of 8 atoms . In the scf calculations I used an ultrasoft pseudopotential so I chose my ecutrho= 8* ecutwfc and also in the ph.x calculations tr2_ph was set to 1 *10^(-19) but I still get that the three first values of the frequencies are negative. Does this confirm the instability of the system?</div><div><br></div><div>SCF INPUT:</div><div><br></div><div><div> &system</div><div> ibrav=0,</div><div> celldm(1)= 9.008277,</div><div> nat=8,</div><div> ntyp= 2,</div><div> ecutwfc =32,</div><div> ecutrho=256,</div><div> occupations='smearing',</div><div> smearing='mv',</div><div> degauss=0.02</div><div><br></div><div>/</div><div> &electrons</div><div> conv_thr=1.D-6,</div><div> mixing_beta=0.3D0,</div><div> mixing_mode='plain',</div><div> diago_david_ndim=2,</div></div><div>.</div><div>.</div><div>.</div><div>.</div><div>.</div><div>etc</div><div><br></div><div>PH INPUT:</div><div><br></div><div><div>&inputph</div><div><br></div><div>tr2_ph=1.0d-19,</div><div>prefix='Graphyne',</div><div>fildvscf='Graphydvscf',</div><div>recover=.true.,</div><div>trans=.true.,</div><div>amass(1)=12.0107,</div><div>amass(2)=1.00794,</div><div>outdir='/home_cluster/fis718/eliemouj/espresso-4.3.2/Graphyne/GRAPHYNEDIR/',</div><div>fildyn='Graphy.dynG'</div><div> /</div><div>0.0 0.0 0.0</div></div><div><br></div><div><br></div><div>The output i got is :</div><div><br></div><div><div> omega( 1) = -11.303890 [THz] = -377.057178 [cm-1]</div><div> omega( 2) = -11.228798 [THz] = -374.552397 [cm-1]</div><div> omega( 3) = -1.493780 [THz] = -49.827127 [cm-1]</div><div> omega( 4) = 1.499866 [THz] = 50.030148 [cm-1]</div><div> omega( 5) = 2.192955 [THz] = 73.149113 [cm-1]</div><div> omega( 6) = 11.690342 [THz] = 389.947822 [cm-1]</div></div><div>.</div><div>.</div><div>.</div><div>.</div><div>.</div><div>.</div><div>.</div><div><br></div><div>Thanks for the help</div><div><br></div><div>Elie Mouhaes</div><div>University of Nottingham</div><div>NG7 2RD</div><div><br></div><div><br></div><div><br></div><div><br></div> </div></body>
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