<p>
Greeting, QE users and experts.
</p>
<p>
I want to calculate vibrational modes of metal atom that absorbed on rutile (TiO2), however, I find pw.x module can't converge at all if I turn off "smearing". I have tried changed mixing_mode from plain to local-TF, reduced mixing_beta to 0.1, but all was in vain.
</p>
<p>
Q1: what's wrong with my system? Does it mean that my system is actually metallic?
</p>
<p>
What's worse, after I completed scf calculation (added smearing with degauss=0.002) and turned to ph.x, convergence oscillated, then exploded after about 50 iterations:
</p>
<p>
1-8:
</p>
<p>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 7.296E-07<br>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 6.558E-05<br>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 1.732E-04<br>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 1.231E-02<br>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 5.254E-03<br>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 5.072E-02<br>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 1.621E-01<br>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 4.011E+00<br>
</p><div>
<br>
</div>
51-58:
<p></p>
<p>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 2.663E+04<br>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 1.416E+07<br>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 6.096E+06<br>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 1.458E+06<br>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 2.034E+06<br>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 1.185E+07<br>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 6.708E+06<br>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 2.834E+06<br>
</p><p>
99-100:
</p>
<p>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 2.264E+11<br>
thresh= 1.000E-02 alpha_mix = 0.700 |ddv_scf|^2 = 3.491E+10<br>
</p><p>
Q2: note that in ph.x, I can't find ways as smearing in pw.x module, what can I do to improve convergence? I have searched posts in archive, it seems that explosion of convergence means "something" but I don't know what exactly that is, could anybody tell me?
</p>
<p>
<br>
</p>
<p>
Thanks in advance.
</p>
<p>
<br>
</p>
<p>
Huang Yike, PhD candidate.
</p>
Dalian Institute of Chemical Physics, CAS, China.
<p></p>
<p></p>