[Pw_forum] Phonon of ScN

[Ari P Seitsonen]

Dear Sohail Ahmad,

   Did you treat the LO-TO splitting? The material seems to have very large 
splitting, in the article that you cite 335 cm-1, even if the band gap 
is very small. If not, you can see for example the end of
http://people.sissa.it/~degironc/QE-Tutorial/tutorial_phon.htm
on how to calculate that with QE/pw.x+ph.x.

     Greetings from Paris,

        apsi

-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
   Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
     Ecole Normale Supérieure (ENS), Département de Chimie, Paris
     Mobile (F) : +33 789 37 24 25    (CH) : +41 79 71 90 935


On Sat, 23 Apr 2016, Sohail Ahmad wrote:

> Dear All,
> I am trying to calculate phonon frequencies of ScN,
> but i am not getting as reported by Prof Umesh Waghmare group
> Journal of Applied Physics, 107, 03715 (2010)
> Electronic structure, phonons and thermal properties of ScN, ZrN and HfN
> 
> I am not getting any frequency around 600 cm-1.
> Pls check and suggest any mistakes
> -----------------------------------------------------------------------------
> Output (and input )of my calculation at Gamma for ScN is as follows
> 
> q = (    0.000000000   0.000000000   0.000000000 )
> 
>  **************************************************************************
>      freq (    1) =       0.073720 [THz] =       2.459027 [cm-1]
>      freq (    2) =       0.312948 [THz] =      10.438836 [cm-1]
>      freq (    3) =       0.312948 [THz] =      10.438836 [cm-1]
>      freq (    4) =      10.407119 [THz] =     347.144126 [cm-1]
>      freq (    5) =      10.472361 [THz] =     349.320372 [cm-1]
>      freq (    6) =      10.472361 [THz] =     349.320372 [cm-1]
>  **************************************************************************
> 
>      Mode symmetry, C_3v (3m)   point group:
> 
>      freq (  1 -  1) =          2.5  [cm-1]   --> A_1  L_1        I+R
>      freq (  2 -  3) =         10.4  [cm-1]   --> E    L_3        I+R
>      freq (  4 -  4) =        347.1  [cm-1]   --> A_1  L_1        I+R
>      freq (  5 -  6) =        349.3  [cm-1]   --> E    L_3        I+R
>  --------------------------------------------------------------------------------------
> &SYSTEM
>    ibrav=2,
>    a=4.501,
>    nat=2, ntyp=2,
>    ecutwfc = 250, ecutrho = 1000,
>    nbnd=15,
>    occupations = 'smearing', smearing = 'gaussian', degauss = 0.001,
>    nspin = 2,
>    starting_magnetization(1)=0.1d0,
>   /
>  &ELECTRONS
>     conv_thr =  1.0d-9,
>     mixing_beta = 0.3,
>  /
>  ATOMIC_SPECIES
>   Sc 44.956   Sc.pw91-nsp-van.UPF
>   N  14.007   N.pw91-van_ak.UPF
>  ATOMIC_POSITIONS {angstrom}
>  Sc  -0.044377705  -0.044377705  -0.044377705
>  N    2.294877705   2.294877705   2.294877705
>  K_POINTS automatic
> 12 12 12 1 1 1
> --------------------------------------------------------------------
>  &inputph
>  tr2_ph = 1.0d-16,
>  amass(1) = 44.956,
>  amass(2) = 14.007,
>  prefix = 'ScN',
>  !epsil=.true.,  ! set this to true for polar semiconductors !
>  outdir = '/scratch/ScN-scf-30591'
>  fildyn = 'ScN.dynG',
> /
> 0.0  0.0  0.0
> 
> ---------------------------------------------------------------------
> Dr. Sohail Ahmad
> King Khalid UniversityAbha, Saudi Arabia
> --------------------------------------------------------------------
> 
>