Dear Lorenzo, Thanks for your reply. I may missing something here, I appreciate if you explain. How do you define the amplitude of u(R) vector in derivative calculations? 3N normal coordinates related to 3*N normal modes are displaced compared to relaxed positions, if I’m right.
Best, Sam > On 1 Mar 2017, at 11:36, Lorenzo Paulatto <[email protected]> > wrote: > > On Wednesday, March 1, 2017 11:54:01 AM CET Azadi, Sam wrote: >> Dear Experts, >> >> I’m interested to know that how the amplitude of atomic displacements are >> defined in DFPT calculations? > > Hello, in density function perturbation theory, contrary to finite-differenes > method, there is no atom displacement: quantum-mechanics perturbation theory > is used. > > See this reference: <http://journals.aps.org/rmp/abstract/10.1103/RevModPhys. > 73.515> for details on the method how it is implemented in QE. > > Tis lecture from Stefano Baroni to get a quick idea: < https:// > www.dropbox.com/s/xi06fv6oz07j9du/EUSPec%202016%20%281%29.pdf?dl=0> > > > -- > Dr. Lorenzo Paulatto > IdR @ IMPMC -- CNRS & Université Paris 6 > phone: +33 (0)1 442 79822 / skype: paulatz > www: http://www-int.impmc.upmc.fr/~paulatto/ > mail: 23-24/423 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05 > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
