[Pw_forum] LO-TO splitting in complete phonon dispersion using PWSCF

[Lorenzo Paulatto]

LO-TO splitting is a long-range effect, as such it only occurs in the
vicinity of Gamma. You can try to make a copy of the force constant 
file, where you remove the effective charges, i.e. you remove these lines:
  T
       2.2192318      0.0000000      0.0000000
       0.0000000      2.2192318      0.0000000
       0.0000000      0.0000000      3.5742157
     1
      -0.5300825      0.0000000      0.0000000
       0.0000000     -0.5300825      0.0000000
       0.0000000      0.0000000     -2.0015990
     2
      -0.5300825      0.0000000      0.0000000
       0.0000000     -0.5300825      0.0000000
       0.0000000      0.0000000     -2.0015990
     3
       1.0610398      0.0000000      0.0000000
       0.0000000      1.0610398      0.0000000
       0.0000000      0.0000000      4.0034960

and do the dispersion with matdyn again. You can then compare the two 
dispersion to see where the long range LO-TO splitting kicks in.


>
> Also, I want to know the details (or please refer any source or
> tutorial) and difference of *"fleig"* and *"fldyn". *Surprisingly I was
> not able to find any frequencies in fidyn out put file. My out put is as
> follows




-- 
Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
phone: +33 (0)1 44275 084 / skype: paulatz
www:   http://www-int.impmc.upmc.fr/~paulatto/
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