[Pw_forum] phonons

[Carlo Nervi]

Dear QE users,
first of all I apologize if my is a dumb question, and I suspect it's 
impossible... Anyway, here it is:

as chemist I'm looking for a selected vibrational frequency associated 
to a stretching of a particular bond in a crystal.
Since among all vibrations in the crystal I'm interested only in one 
(the bond stretching, and eventually anything else associated with the 
motion of a selected atom), is there any way in QE to compute only this 
mode without the need to compute everything?

Second question: what is the most immediate way (program or tool) to 
assign and find from the output the correct frequency of my vibration? 
Do I have to perform all the complete DOS phonons?

Thank you,
	Carlo

-- 
------------------------------------------------------------
Prof. Carlo Nervi carlo.nervi at unito.it  Tel:+39 0116707507/8
Fax: +39 0116707855      -      Dipartimento di Chimica, via
P. Giuria 7, 10125 Torino, Italy.    http://lem.ch.unito.it/