Re: [Pw_forum] ?propagation direction of LO-TO splitting for dynmat.in file phonon calculation

[Pietro Delugas]

Dear Wei

LO modes should be computed along the direction of the dipoles of 
InfraRed (IR)  active modes.


Anatase is tetragonal, mode dipoles can be either parallel to the axial 
direction or perpendicular to that, in this latter case the relative 
mode has to be  doubly degenerate, and thus any direction perpendicular 
to the axis is OK.


The only important thing is the direction, the module of the q vector 
has no influence on the result.


greetings Pietro


On 25/12/2016 16:24, Wei Li wrote:

Dear Stefano de Gironcoli,

Thanks for your words.

Regarding the anatase bulk tio2, which direction should I choose to 
propagate? And also how large the q(i) is?


thanks, Merry Christmas!

Wei

--
*Wei Li*
PhD student
State Key Lab of Theoretical & Computational Chemistry
Institute of Theoretical Chemistry
Jilin University
Changchun, 130023
P.R. China
Email: liwei0...@gmail.com 


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Re: [Pw_forum] ?propagation direction of LO-TO splitting for dynmat.in file phonon calculation

[Wei Li]

Dear Stefano de Gironcoli,

Thanks for your words.

Regarding the anatase bulk tio2, which direction should I choose to
propagate? And also how large the q(i) is?

thanks, Merry Christmas!

Wei

-- 
*Wei Li*
PhD student
State Key Lab of Theoretical & Computational Chemistry
Institute of Theoretical Chemistry
Jilin University
Changchun, 130023
P.R. China
Email: liwei0...@gmail.com
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Re: [Pw_forum] ​propagation direction of LO-TO splitting for dynmat.in file phonon calculation

[stefano de gironcoli]

Dear Wei Li,

  from the header of the dynmat.f90 source code
!
!  This program
!  - reads a dynamical matrix file produced by the phonon code
!  - adds the nonanalytical part (if Z* and epsilon are read from file),
!applies the chosen Acoustic Sum Rule (if q=0)
!  - diagonalise the dynamical matrix
!  - calculates IR and Raman cross sections (if Z* and Raman tensors
!are read from file, respectively)
!  - writes the results to files, both for inspection and for plotting
!
!  Input data (namelist "input")
!
!  fildyn  character input file containing the dynamical matrix
!(default: fildyn='matdyn')
!  q(3)  realcalculate LO modes (add nonanalytic terms) along
!the direction q (cartesian axis, default: q=(0,0,0) )

the value of the vector q (when different from zero) is interpreted as 
the direction of propagation of the phonons.


stefano

On 25/12/2016 02:20, Wei Li wrote:

​​
​Hi Friends,

I plan to calculate the infrared spectrum of anatase TiO2 bulk using 
pw.x (scf), ph.x calculates phonon frequencies and effective charge 
etc..  Then the dynmat.x is used to calculate LO-TO splitting.


The ph.x calculation is performed at single q, i.e., q=0.0,0.0,0.0 in 
ph.in  file


​
The question is how to define the
​​
propagation direction of LO-TO splitting, q(i), i=1,2,3, in the 
dynmat.in  file?


For instance, how to set q(1),q(2),q(3)?​






--
*Wei Li*
PhD student
State Key Lab of Theoretical & Computational Chemistry
Institute of Theoretical Chemistry
Jilin University
Changchun, 130023
P.R. China
Email: liwei0...@gmail.com 


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http://pwscf.org/mailman/listinfo/pw_forum



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[Pw_forum] ​propagation direction of LO-TO splitting for dynmat.in file phonon calculation

[Wei Li]

​​
​Hi Friends,

I plan to calculate the infrared spectrum of anatase TiO2 bulk using pw.x
(scf), ph.x calculates phonon frequencies and effective charge etc..  Then
the dynmat.x is used to calculate LO-TO splitting.

The ph.x calculation is performed at single q, i.e., q=0.0,0.0,0.0 in ph.in
file

​
The question is how to define the
​​
propagation direction of LO-TO splitting, q(i), i=1,2,3, in the dynmat.in
file?

For instance, how to set q(1),q(2),q(3)?​






-- 
*Wei Li*
PhD student
State Key Lab of Theoretical & Computational Chemistry
Institute of Theoretical Chemistry
Jilin University
Changchun, 130023
P.R. China
Email: liwei0...@gmail.com
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