[Pw_forum] Phonon branch enumeration
Jeffrey Mullen
jtmullen at ncsu.edu
Wed Mar 11 03:32:46 CET 2009
Thanks for the recommendation. I have performed the calculation with the
iverbosity set to 1. It will take me a while to parse it and understand
the output, but if I can figure out the relationships, I will attempt to
code the ordering into the application.
Cheers
Jeff Mullen
North Carolina State University
Dal Corso Andrea wrote:
>
>It is an interesting idea. I think it is possible to make the
>symmetry classification of the displacements patterns with the same
>routine that makes the symmetry classification of the eigenvectors
>of the dynamical matrix. Presently, this is not done. You can
>code this feature yourself or just use iverbosity=1. With this option
>the code writes the displacement patterns and you can
>check their symmetry.
>
>Andrea
>
>
>
>
>
>>Cheers
>>Jeff
>>
>>
>>
>>e kb wrote:
>>
>>
>>
>>>Dear Jeff,
>>>I am definitely not an expert on the topic but I'd like to understand
>>>your question better.
>>>
>>> Mode symmetry, D_6h(6/mmm) point group:
>>>
>>> omega( 1 - 1) = -37.4 [cm-1] --> A_2u I
>>> omega( 2 - 3) = -33.9 [cm-1] --> E_1u I
>>> omega( 4 - 4) = 863.3 [cm-1] --> B_2g
>>> omega( 5 - 6) = 1336.0 [cm-1] --> E_2g
>>>
>>>So you have the irr. representations and the values for omega (values
>>>are printed with higher precision in the previous part after
>>>diagonalization as you reported). What exactly do you want to know
>>>more (that you cannot check from a book on group theory) ?
>>>
>>>Emine Kucukbenli, grad. student, SISSA, Italy.
>>>
>>>--- On *Tue, 3/10/09, Jeffrey Mullen /<jtmullen at ncsu.edu>/* wrote:
>>>
>>> From: Jeffrey Mullen <jtmullen at ncsu.edu>
>>> Subject: [Pw_forum] Phonon branch enumeration
>>> To: pw_forum at pwscf.org
>>> Date: Tuesday, March 10, 2009, 2:34 AM
>>>
>>>Greetings
>>>
>>>I am testing electron-phonon interaction calculations with graphene and
>>>have encountered a problem enumerating the resulting phonon branches.
>>>When I run the ph.x calculation at the q(0 0 0), the code calculates 4
>>>representations:
>>>
>>> Representation # 1 modes # 1 2
>>> Representation # 2 mode # 3
>>> Representation # 3 mode # 4
>>> Representation # 4 modes # 5 6
>>>
>>>
>>>When the values for omega are calculated, the results are:
>>>
>>>**************************************************************************
>>> omega( 1) = -1.119851 [THz] = -37.354451 [cm-1]
>>> omega( 2) = -1.016557 [THz] = -33.908905
>>>[cm-1]
>>> omega( 3) = -1.016557 [THz] = -33.908905 [cm-1]
>>> omega( 4) = 25.882237 [THz] = 863.344237 [cm-1]
>>> omega( 5) = 40.051667 [THz] = 1335.988701 [cm-1]
>>> omega( 6) = 40.051667 [THz] = 1335.988701 [cm-1]
>>>**************************************************************************
>>>
>>>
>>>with the following mode symmetries:
>>>
>>> Mode symmetry, D_6h(6/mmm) point group:
>>>
>>> omega( 1 - 1) = -37.4 [cm-1] --> A_2u I
>>> omega( 2 - 3) = -33.9 [cm-1] --> E_1u I
>>> omega( 4 - 4) = 863.3 [cm-1] --> B_2g
>>> omega( 5 - 6) = 1336.0 [cm-1] --> E_2g R
>>>
>>>
>>>My question is one of ordering. How do I extract which omega(##)
>>>corresponds to which representation/mode?
>>>
>>>Thanks
>>>Jeff Mullen
>>>North Carolina State
>>>University
>>>
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