Dear Umesh
I'm not sure I understand your problem.
if acoustic modes and optical ones have different symmetries (LA and
TO for instance in specific directins) they can overlap in frequency but
still be distinct objects that you can identify by examining the
eigenvectors. If they have the same symmetry (typically no symmetry at
all for a generic q direction in the BZ) they interact and get mixed so
there aren't purely acoustic or purely optical modes any more.
stefano
On 01/08/2015 13:21, Umesh Roy wrote:
Dear All,
I have calculated modes of vibration of Iron in different
directions for a fix phonon wave vector q (in a large number of
directions). Since in Quantum espresso phonon modes are printed in
increasing order for a given q vector. For a small group of q the
acoustic and optical branches do not overlap so, we can easily
separate out the acoustic branch from the optical branch. As we
increase the magnitude of q the acoustic branch and the optical branch
get mixed up. So , how to separate out the acoustic modes or is there
any way of filtering the optical modes?
Thank you in advance
/*Umesh Chandra Roy*
Research Scholar, School of Physical Sciences
Jawaharlal Nehru University, New Delhi-110067,
/
/India.
/
/Email:*[email protected]* <mailto:email%[email protected]>
/
/Mobile:*+919868022722*//*
*/
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