Re: [Pw_forum] Phonon freqencies

2017-08-24 Thread Sonu Kumar 
To know TO and LO modes, you have to
specify the direction in k-space along which you want to see the splitting.

Also, see the post
http://qe-forge.org/pipermail/pw_forum/2014-November/105682.html

bests,
sonu


On Thu, Aug 24, 2017 at 2:58 PM, Uttam Paliwal  wrote:

> Dear QE users
> I am computing phonon frequencies for BeS. I am attaching here the output
> file part
>
>
>
>  q = (0.0   0.0   0.0 )
>
>  ***
> ***
>  freq (1) =   0.105756 [THz] =   3.527650 [cm-1]
>  freq (2) =   0.105756 [THz] =   3.527650 [cm-1]
>  freq (3) =   0.105756 [THz] =   3.527650 [cm-1]
>  freq (4) =  16.460235 [THz] = 549.054328 [cm-1]
>  freq (5) =  16.460235 [THz] = 549.054328 [cm-1]
>  freq (6) =  16.460235 [THz] = 549.054328 [cm-1]
>  ***
> ***
>
>  Mode symmetry, T_d (-43m)  point group:
>
>  freq (  1 -  3) =  3.5  [cm-1]   --> T_2  G_15 P_4   I+R
>  freq (  4 -  6) =549.1  [cm-1]   --> T_2  G_15 P_4   I+R
>
>
> 
> **
> these are TO (Transverse Optical) or LO (Longitudinal Optical), how to
> know. please suggest
>
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>
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[Pw_forum] Phonon freqencies

2017-08-24 Thread Uttam Paliwal 
Dear QE users
I am computing phonon frequencies for BeS. I am attaching here the output
file part



 q = (0.0   0.0   0.0 )

 **
 freq (1) =   0.105756 [THz] =   3.527650 [cm-1]
 freq (2) =   0.105756 [THz] =   3.527650 [cm-1]
 freq (3) =   0.105756 [THz] =   3.527650 [cm-1]
 freq (4) =  16.460235 [THz] = 549.054328 [cm-1]
 freq (5) =  16.460235 [THz] = 549.054328 [cm-1]
 freq (6) =  16.460235 [THz] = 549.054328 [cm-1]
 **

 Mode symmetry, T_d (-43m)  point group:

 freq (  1 -  3) =  3.5  [cm-1]   --> T_2  G_15 P_4   I+R
 freq (  4 -  6) =549.1  [cm-1]   --> T_2  G_15 P_4   I+R


**
these are TO (Transverse Optical) or LO (Longitudinal Optical), how to
know. please suggest
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