[QE-users] Gamma point phonon calculation is not consistent

[wang1968000]

Hi. QE users.
I have calculate Gamma point phonon and phonon dispersion on black phosphorus.
But the phonon modes are not same in only Gamma point calculation and several q point calculations.


This is the results coming from only Gamma point calculation.
 Diagonalizing the dynamical matrix


     q = (    0.000000000   0.000000000   0.000000000 ) 


 **************************************************************************
     freq (    1) =      -0.038897 [THz] =      -1.297458 [cm-1]
     freq (    2) =      -0.031677 [THz] =      -1.056638 [cm-1]
     freq (    3) =       0.027926 [THz] =       0.931519 [cm-1]
     freq (    4) =       2.928955 [THz] =      97.699418 [cm-1]
     freq (    5) =       5.638698 [THz] =     188.086708 [cm-1]
     freq (    6) =       6.639162 [THz] =     221.458590 [cm-1]
     freq (    7) =      10.953491 [THz] =     365.369131 [cm-1]
     freq (    8) =      12.684841 [THz] =     423.120746 [cm-1]
     freq (    9) =      12.722708 [THz] =     424.383866 [cm-1]
     freq (   10) =      12.745234 [THz] =     425.135234 [cm-1]
     freq (   11) =      13.570613 [THz] =     452.666939 [cm-1]
     freq (   12) =      13.874216 [THz] =     462.794044 [cm-1]
 **************************************************************************


     Mode symmetry, D_2h (mmm)  point group:


     freq (  1 -  1) =         -1.3  [cm-1]   --> B_3u            I  
     freq (  2 -  2) =         -1.1  [cm-1]   --> B_1u            I  
     freq (  3 -  3) =          0.9  [cm-1]   --> B_2u            I  
     freq (  4 -  4) =         97.7  [cm-1]   --> B_3u            I  
     freq (  5 -  5) =        188.1  [cm-1]   --> B_3g            R  
     freq (  6 -  6) =        221.5  [cm-1]   --> B_2g            R  
     freq (  7 -  7) =        365.4  [cm-1]   --> A_g             R  
     freq (  8 -  8) =        423.1  [cm-1]   --> A_u                
     freq (  9 -  9) =        424.4  [cm-1]   --> B_1g            R  
     freq ( 10 - 10) =        425.1  [cm-1]   --> B_2g            R  
     freq ( 11 - 11) =        452.7  [cm-1]   --> A_g             R  
     freq ( 12 - 12) =        462.8  [cm-1]   --> B_1u            I  




This results comes from Gamma point  in several q point calculation.
      q = (    0.000000000   0.000000000   0.000000000 ) 


 **************************************************************************
     freq (    1) =       0.294821 [THz] =       9.834157 [cm-1]
     freq (    2) =       0.531839 [THz] =      17.740255 [cm-1]
     freq (    3) =       0.538183 [THz] =      17.951848 [cm-1]
     freq (    4) =       2.934902 [THz] =      97.897792 [cm-1]
     freq (    5) =       5.651273 [THz] =     188.506166 [cm-1]
     freq (    6) =       6.641297 [THz] =     221.529834 [cm-1]
     freq (    7) =      10.953478 [THz] =     365.368700 [cm-1]
     freq (    8) =      12.689602 [THz] =     423.279546 [cm-1]
     freq (    9) =      12.724636 [THz] =     424.448167 [cm-1]
     freq (   10) =      12.750003 [THz] =     425.294313 [cm-1]
     freq (   11) =      13.570944 [THz] =     452.677974 [cm-1]
     freq (   12) =      13.879876 [THz] =     462.982823 [cm-1]
 **************************************************************************


     Mode symmetry, D_2h (mmm)  point group:


     freq (  1 -  1) =          9.8  [cm-1]   --> B_1u            I  
     freq (  2 -  2) =         17.7  [cm-1]   --> B_3u            I  
     freq (  3 -  3) =         18.0  [cm-1]   --> B_2u            I  
     freq (  4 -  4) =         97.9  [cm-1]   --> B_2u            I  
     freq (  5 -  5) =        188.5  [cm-1]   --> B_2g            R  
     freq (  6 -  6) =        221.5  [cm-1]   --> B_3g            R  
     freq (  7 -  7) =        365.4  [cm-1]   --> A_g             R  
     freq (  8 -  8) =        423.3  [cm-1]   --> A_u                
     freq (  9 -  9) =        424.4  [cm-1]   --> B_1g            R  
     freq ( 10 - 10) =        425.3  [cm-1]   --> B_3g            R  
     freq ( 11 - 11) =        452.7  [cm-1]   --> A_g             R  
     freq ( 12 - 12) =        463.0  [cm-1]   --> B_1u            I  




Why these two parts are not same?
The structure I already optimised.


TW.
Department of Physics
Tohoku Unviersity
Email: wang1968000 at 163.com

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20191030/29877eaa/attachment.html>