[Pw_forum] LO-TO splitting in complete phonon dispersion using PWSCF

[Kondaiah Samudrala]

Dear SIr,

Sorry for not provide the symmetry of the system. My system crystallizes in
Body centered tetragonal (ibrav=7); 3 atoms/cell with celldm(1)=   8.017350
and celldm(3)=   1.660948.

In detail, I found huge splitting of the LO and TO modes of IR modes at
ambient pressure (in the Gamma point level), where as the  gap was closed
under pressure. The same I want to check with complete dispersion as well
as try to compute the effect on other special points in IBZ.  Of course I
finished the phonon dispersion calculations with LO-TO splitting but I am
not able to zoom out  the LO-TO (or LA-TA) in other directions

Also, I want to know the details (or please refer any source or tutorial)
and difference of *"fleig"* and *"fldyn". *Surprisingly I was not able to
find any frequencies in fidyn out put file. My out put is as follows

    Dynamical  Matrix in cartesian axes

     q = (    0.010000000   0.000000000   0.000000000 )

    1    1
  0.04011368  0.00000000    0.00000000  0.00000000    0.00000000  0.00008840
  0.00000000  0.00000000    0.03267074  0.00000000    0.00000000  0.00000000
  0.00000000 -0.00008840    0.00000000  0.00000000    0.27929359  0.00000000
    1    2
  0.01491749  0.00000000    0.00000000  0.00000000    0.00000000 -0.00016204
  0.00000000  0.00000000    0.00747601  0.00000000    0.00000000  0.00000000


If possible please suggest me the high symmetry points of the BCT structure
for PWSCF with c/a> 1.

My Basis vectors are

     crystal axes: (cart. coord. in units of alat)
               a(1) = (   0.500000  -0.500000   0.830474 )
               a(2) = (   0.500000   0.500000   0.830474 )
               a(3) = (  -0.500000  -0.500000   0.830474 )


Thanks in advance

with regards
S. Appalakondaiah
PhD student
University of Hyderabad
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20141121/16b1270b/attachment.html>