[Pw_forum] negative el-ph coupling constant lambda

[陳 少華]

Dear Eyvaz and forum's members,

When I calculated the el-ph coupling constant \lambda
of material.I find some negative value

  Electron-phonon coupling constant, lambda

 Broadening   0.0100 lambda       0.0008 dos_el  
0.3719
 Broadening   0.0200 lambda       0.0012 dos_el  
0.3674
 Broadening   0.0300 lambda       0.0021 dos_el  
0.3565
 Broadening   0.0400 lambda      -0.0098 dos_el  
0.3821
 Broadening   0.0500 lambda      -0.0303 dos_el  
0.5231
 Broadening   0.0600 lambda      -0.0394 dos_el  
0.7545
 Broadening   0.0700 lambda      -0.0408 dos_el  
1.0409
 Broadening   0.0800 lambda      -0.0382 dos_el  
1.3767
 Broadening   0.0900 lambda      -0.0333 dos_el  
1.7603
 Broadening   0.1000 lambda      -0.0274 dos_el  
2.1824

Also find some negative value in gam.line
e.g.
  24     0.0000  0.0000  0.0000  -0.0001  0.0000
-0.0001    *****    0.0000  0.0000

But no negative frequency found in matdyn.freq

I thought -\lambda comes from -\gamma (phonon
linewidth), and -\gamma  comes from -\omega
(frequency) by its definitions.

So I wonder why I got -\lambda and -\gamma (It should
be >=0)
even frequency \omega seems fine (no negative) ???

Should I just try check convergence of \gamma in
dependent on cutoff energy and k-points sampling ?
(from forum's "search archive", title " 3 questions
about elph file of Calculation of electron-phonon
interaction coefficients" suggestions )

Thanks in advance

max
PHD candidate
Physics department, National Taiwan University,Taiwan


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