On 12/06/2022 12:00, simon rombauer wrote:
1) Why is it not possible to set epsil = .true., lraman .true. ?
because the system is (treated as) a metal: you are using a broadening
2) Is it normal that the ph.x code takes a lot of comupting time compared to pw.x scf, nscf, bands calculations? (ETO phonon at gamma took over 13 h)
it depends. Plain (GGA, normconserving) phonon calculations should take no more time than (a small factor depending upon the phonon wave-vector) * (time needed for a scf calculation) * (number of linear-response calculations = 3* number of atoms * number of wave-vectors). Ultrasoft phonons are definitely slower. DFT+U don't know, might be slower as well. It depends upon the number ot terms appearing in the linear-response calculation
3) Almost all phonon frequencies are negative, which indicates instabilities in the system (?), I've run vc-relax calculations and used the new lattice parameters but got the same results, any idea what these negative frequencies could tell me?
(negative => imaginary actually) You should first of all figure out whether they are an artifact of the calculation or not. For sure, your threshold for linear-response convergence (tr2_ph) is too large. Have you tried a simpler version of a similar system?
4) Is it possible obtain the dielectric function for these materials in a different way?
For effective charges you may use the Berry's phase approach
I hope you are still around and thank you for reading :)
if you are referring to the mailing list: yes, it still works, except for people using @gmail.com addresses, and for those who don't check their spam folder :-(
Paolo
Have a nice day, Simon Rombauer Physics student University of Augsburg _______________________________________________ The Quantum ESPRESSO community stands by the Ukrainian people and expresses its concerns about the devastating effects that the Russian military offensive has on their country and on the free and peaceful scientific, cultural, and economic cooperation amongst peoples _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
-- Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222 _______________________________________________ The Quantum ESPRESSO community stands by the Ukrainian people and expresses its concerns about the devastating effects that the Russian military offensive has on their country and on the free and peaceful scientific, cultural, and economic cooperation amongst peoples _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
