[Pw_forum] LO-TO splitting in dynmat.x

xirainbow nkxirainbow at gmail.com
Fri Apr 29 07:30:31 CEST 2011

Dear Sonu Kumar
What you said is reasonable;)

I have two little questions.
Does LO-TO splitting must disappear at the boundary of Brillouin zone?

I can understand the LO-TO splitting near Gamma point.
However, at Gamma point(not  near Gamma point), q=0. When q is zero, there
is no longitude and transverse mode. Why are there LO-TO splitting at Gamma


On Fri, Apr 29, 2011 at 1:21 PM, sonu kumar <1009ukumar at gmail.com> wrote:

> Dear All QE users,
> i am sorry again, as i havn't corrected the subject title.
> (2) only cubic crystals has LO and TO braches.
> crystals ( having considerable values of macroscopic dielectric constant [
> i suppose
> epsilon infinity] and born effective charges, as pointed  out by Prof.
> Eyvaz Isaev) with low symmetry can, also, have LO-TO splitting. But this can
> be  different in different symmetry directions, so one has to search all
> symmetry directions for this splitting.
> For cubic crystals splitting is equal in all directions.
> with regards,
> --
> Sonu Kumar
> Phd Student
> Physics Department
> Indian Institute of Technology
> Delhi-110016, India
> web:-http://www.iitd.ac.in/
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Hui Wang
School of physics, Fudan University, Shanghai, China
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