The ABINIT Users Mailing List ( CLOSED )

["Aldo Humberto Romero" <aromero@qro.cinvestav.mx>]

Dear Gao

A more systematic way to answer your question is basically
that you perform the analysis of degeneracies and characters
from Abinit, with this and the symmetry group and wickoff
positions of your crystalline system, you can go straigth into the
Bilbao server and by looking at the characters you can
get the corresponding character(check the application SAM in this server).
What we did at that time it is what automatically Abinit
does with this analysis (at that time I was not aware of that
capability within Abinit)


Regards

-aldo.

-> ->
-> Dear Prof. Romero,
->
->
->
-> Thank you very much for your quick response to my problems.
->
->
->
-> Yes, your answer is just what I want to ask for. I have read your paper
-> 'Silent Raman modes in zinc oxide and related nitrides'in JAP. That's
-> instructive to my understanding in LO-TO splitting and thanks for you
-> recommendation.
->
->
->
-> However, here I want to raise another basic question on the assignment of
-> vibrational Modes to Phonon frequencies with LO-TO splitting, How to find
-> the irreducible representation just using the eigenvector of a vibrational
-> mode? I can dissolve the reducible representation into IR  using
-> representation theory. for example, for ZnO(spacegroup,No.186) there
-> exists the relation 2A1+2B1+2E1+2E2 at the Brillouin-zone center (q=0),
-> and also I have obtain the eigenvector for my phonon frequencies.
->
->
->
-> Would you like to instruct me use the bilbao crystallographic server and
-> eigenvectors
-> to assign the symmetry mode?
->
->
->
-> Thank you very much, and look forward to hearing from you.
->
->
-> Regards,
->
->
->
-> Tao
->
->
->
-> BTW, please see the eigenvectors in the attatchment.
->
->
->
->
->> Date: Sat, 9 May 2009 14:02:32 -0500
->> From: aromero@qro.cinvestav.mx
->> To: forum@abinit.org
->> CC: forum@abinit.org
->> Subject: Re: [abinit-forum] The Assignment of Vibrational Modes to
->> Phonon Frequencies when LO-TO Splitting
->>
->> Dear Gao
->>
->> maybe I am confussed about your question, but the assignments
->> of the irreducible representation could be done by looking
->> at the symmetries of the eigenvectors (look at the
->> vectors ad you can use the bilbao crystallographic erver
->> to assign the symmetry)... at least that is
->> what we did in that paper and in a subsequent paper
->> jap vol 97 053516 (2005), where we look at the so called
->> silent modes.
->>
->> I am not sure this is what you want... but at least I hope
->> it is related to
->>
->> regards
->>
->> -ald.
->>
->>
->>
->> ->
->> -> Dear Colleague,
->> ->
->> ->
->> ->
->> -> When I use ABINIT to practise to reproduce the LO-TO splitting for
->> ZnO
->> -> "Pressure dependence of the lattice dynamics of ZnO: An ab initio
->> -> approach, published on PHYSICAL REVIEW B 69,094306(2004)", I got
->> into
->> -> trouble at the assignment of vibrational mode for the LO-TO
->> splitting.
->> ->
->> ->
->> ->
->> -> I can assign the correct irreducible representation to Phonon
->> frequencies
->> -> when without LO-TO splitting, e.g.,for ZnO(spacegroup,No.186) there
->> exists
->> -> the relation 2A1+2B1+2E1+2E2 at the Brillouin-zone center (q=0),
->> i.e.,
->> ->
->> ->
->> ->
->> -> ' Phonon wavevector (reduced coordinates) : 0.00000 0.00000 0.00000
->> -> Phonon energies in Hartree :
->> -> 0.000000E+00 0.000000E+00 0.000000E+00 3.799350E-04 3.799358E-04
->> -> 1.143489E-03 1.587916E-03 1.587917E-03 1.737701E-03 1.737703E-03
->> -> 1.747231E-03 2.422538E-03
->> -> Phonon frequencies in cm-1 :
->> -> - (0.000000E+00 0.000000E+00 0.000000E+00)A1+E1 (8.338610E+01
->> -> 8.338626E+01)E2
->> -> - (2.509668E+02)B1 (3.485072E+02 3.485076E+02)E1 (3.813812E+02
->> -> 3.813816E+02)E2
->> -> - (3.834728E+02)B1 (5.316857E+02)A1'
->> ->
->> ->
->> -> When approaching GAMMA center along some different direction in
->> -> Brillouin-zone, the calcultion results indicate that there will have
->> LO-TO
->> -> splitting for some vibration mode, but I have no idea on how to
->> assign
->> -> these phonon frequencies to correct vibrational mode. My output file
->> for
->> -> this part is as follow,
->> ->
->> ->
->> ->
->> -> ' Phonon at Gamma, with non-analyticity in the
->> -> direction (cartesian coordinates) 1.00000 0.00000 0.00000
->> -> Phonon energies in Hartree :
->> -> 0.000000E+00 0.000000E+00 0.000000E+00 3.799350E-04 3.799358E-04
->> -> 1.143489E-03 1.587916E-03 1.737701E-03 1.737703E-03 1.747231E-03
->> -> 2.149073E-03 2.422538E-03
->> -> Phonon frequencies in cm-1 :
->> -> - 0.000000E+00 0.000000E+00 0.000000E+00 8.338610E+01 8.338626E+01
->> -> - 2.509668E+02 3.485072E+02 3.813812E+02 3.813816E+02 3.834728E+02
->> -> - 4.716670E+02 5.316857E+02
->> ->
->> -> Phonon at Gamma, with non-analyticity in the
->> -> direction (cartesian coordinates) 0.00000 0.00000 1.00000
->> -> Phonon energies in Hartree :
->> -> 0.000000E+00 0.000000E+00 0.000000E+00 3.799350E-04 3.799358E-04
->> -> 1.143489E-03 1.587916E-03 1.587917E-03 1.737701E-03 1.737703E-03
->> -> 2.422538E-03 2.522783E-03
->> -> Phonon frequencies in cm-1 :
->> -> - 0.000000E+00 0.000000E+00 0.000000E+00 8.338610E+01 8.338626E+01
->> -> - 2.509668E+02 3.485072E+02 3.485076E+02 3.813812E+02 3.813816E+02
->> -> - 5.316857E+02 5.536868E+02
->> ->
->> -> Phonon at Gamma, with non-analyticity in the
->> -> direction (cartesian coordinates) 0.00000 1.00000 0.00000
->> -> Phonon energies in Hartree :
->> -> 0.000000E+00 0.000000E+00 0.000000E+00 3.799350E-04 3.799358E-04
->> -> 1.143489E-03 1.587917E-03 1.737701E-03 1.737703E-03 1.747231E-03
->> -> 2.149072E-03 2.422538E-03
->> -> Phonon frequencies in cm-1 :
->> -> - 0.000000E+00 0.000000E+00 0.000000E+00 8.338610E+01 8.338626E+01
->> -> - 2.509668E+02 3.485076E+02 3.813812E+02 3.813816E+02 3.834728E+02
->> -> - 4.716668E+02 5.316857E+02'
->> ->
->> ->
->> ->
->> -> I am quiet confused on whether the assignment of these phonon
->> -> frequencies(along different directions) are same as q=0 without
->> LO-TO
->> -> splitting or not. Would you like to help me assign these Phonon
->> -> frequencies to the correct vibrational modes? Any suggestion will be
->> -> appreciated.
->> ->
->> ->
->> ->
->> -> Thank you very much.
->> ->
->> ->
->> ->
->> -> Best,
->> ->
->> ->
->> ->
->> -> Tao
->> ->
->> ->
->> ->
->> -> BTW, my files including log, input and output files are enclosed as
->> -> attachment.
->> ->
->> -> _________________________________________________________________
->> -> Messenger��ȫ�������ģ������޸�ϵͳ©��������Messenger��ȫ��
->> -> http://im.live.cn/safe/
->>
->>
->> --
->>
->> Prof. Aldo Humberto Romero
->> CINVESTAV-Unidad Queretaro
->> Libramiento Norponiente 2000
->> CP 76230, Queretaro, QRO, Mexico
->> tel: 442 211 9909
->> fax: 442 211 9938
->>
->> email: aromero@qro.cinvestav.mx
->> aldorome@gmail.com
->> www: qro.cinvestav.mx/~aromero
->>
->
-> _________________________________________________________________
-> 上MClub和Messenger好友一起都市寻宝！
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-- 

Prof. Aldo Humberto Romero
CINVESTAV-Unidad Queretaro
Libramiento Norponiente 2000
CP 76230, Queretaro, QRO, Mexico
tel: 442 211 9909
fax: 442 211 9938

email: aromero@qro.cinvestav.mx
        aldorome@gmail.com
www: qro.cinvestav.mx/~aromero