<div dir="ltr"><div><div><div><div><div><div><div><div>Dear all;<br><br></div>I am trying to do phonon calculations for the bulk BP (crystal cell contains 8 atoms) <br>space group Cmce (No. 64), point group D_2h.<br></div>From the symmetry consideration there should be 12 irreducible representations.<br><br></div><div>Below I include part of my scf input:<br><font size="1"> &SYSTEM<br> ibrav = 0 ,<br> A = 1 ,</font><br><font size="1">CELL_PARAMETERS {alat} <br> 3.2982000000 0.0000000000 0.0000000000<br> 0.0000000000 10.1197000000 0.0000000000<br> 0.0000000000 0.0000000000 4.1209000000<br>ATOMIC_SPECIES<br> P 30.97 P.pz-hgh.UPF<br>ATOMIC_POSITIONS {crystal}<br>P -0.000000000 0.106448467 0.071443342<br>P 0.500000000 0.893551533 0.571443372<br>P -0.000000000 0.893551533 0.928556658<br>P 0.500000000 0.106448467 0.428556628<br>P 0.500000000 0.606447305 0.071444660<br>P 0.000000000 0.393552695 0.571444694<br>P 0.500000000 0.393552695 0.928555340<br>P 0.000000000 0.606447305 0.428555306 <br>K_POINTS automatic <br> 15 5 12 0 0 0</font><br><br></div>Unfortunatly, the code sees different symmetry modes C_2h with 24 irreducible representations, instead of D_2h.<br></div>I checked that QE during the structure relaxation does not break the symmetry of the crystal<br></div>- both input and output structure have the same proper symmetry (No. 64) <br>(I checked it by used of the Bilbao crystallographic server <a href="http://www.cryst.ehu.es/">http://www.cryst.ehu.es/</a>).<br></div><div>Thus, the phonon code should read the proper one as well.<br></div><div><br>Below I include part of my phonon output:<br><font size="1"> Mode symmetry, C_2h (2/m) point group:<br><br> freq ( 1 - 1) = -5.4 [cm-1] --> B_u I <br> freq ( 2 - 2) = -3.2 [cm-1] --> B_u I <br> freq ( 3 - 3) = 8.5 [cm-1] --> A_u I <br> freq ( 4 - 4) = 40.5 [cm-1] --> B_u I <br> freq ( 5 - 5) = 52.0 [cm-1] --> A_u I <br> freq ( 6 - 6) = 95.5 [cm-1] --> B_u I <br> freq ( 7 - 7) = 101.7 [cm-1] --> B_u I <br> freq ( 8 - 8) = 152.3 [cm-1] --> B_u I <br> freq ( 9 - 9) = 179.2 [cm-1] --> B_g R <br> freq ( 10 - 10) = 182.3 [cm-1] --> B_g R <br> freq ( 11 - 11) = 202.4 [cm-1] --> A_g R <br> freq ( 12 - 12) = 216.9 [cm-1] --> A_g R <br> freq ( 13 - 13) = 361.7 [cm-1] --> A_g R <br> freq ( 14 - 14) = 363.2 [cm-1] --> A_g R <br> freq ( 15 - 15) = 392.8 [cm-1] --> A_g R <br> freq ( 16 - 16) = 396.6 [cm-1] --> A_g R <br> freq ( 17 - 17) = 415.3 [cm-1] --> A_u I <br> freq ( 18 - 18) = 420.2 [cm-1] --> B_g R <br> freq ( 19 - 19) = 420.3 [cm-1] --> A_u I <br> freq ( 20 - 20) = 421.2 [cm-1] --> B_g R <br> freq ( 21 - 21) = 432.5 [cm-1] --> A_g R <br> freq ( 22 - 22) = 448.3 [cm-1] --> A_g R <br> freq ( 23 - 23) = 458.1 [cm-1] --> B_u I <br> freq ( 24 - 24) = 458.6 [cm-1] --> B_u I </font><br><br></div>Do you have any suggestions what is the problem?<br></div><div>Many thanks in advance.<br></div><div><br></div>Best regards<br></div>Magda Birowska<br>-- <br><div><div><div><div><div><div><div><div><div><div class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div><div><div><div><i>Magdalena Popielska (Birowska), PhD<br></i></div><i><br></i></div><i>Faculty of Physics<br></i></div><i>University of Warsaw<br><br></i></div><i>ul. Pasteura 5, PL-02-093 Warszawa room no. 5.02<br></i></div><div><i>Phone: 22 55 32902 (Office)<br></i></div><i>Email: <a target="_blank" href="mailto:Magdalena.Birowska@fuw.edu.pl">Magdalena.Birowska@fuw.edu.pl</a></i><br></div></div></div></div></div></div></div></div>
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