[QE-users] Doubt regarding the phonon calculations of RbPbI3

[Anupriya Nyayban]

I have calculated the phonon dispersion of orthorhombic RbPbI3 (Pnma) using
"PHONON" as implemented in Quantum Espresso and found the negative
frequencies ( which should not be present as suggested in
https://doi.org/10.1063/1.5131575). It would be great help if you suggest
to me where I am doing wrong!!! I have provided the computational details
below:
1) The structure first is being relaxed and then the convergence tests are
performed for Ecut, Kmesh and Lattice parameters.
2) Using the relaxed structure with converged parameters, SCF is performed
with cov_thr=1.0d-8 (ecutwfc=70, ecutrho=600, kmesh=12*6*3); phonon
calculation is performed with tr2_ph=1.0d-14 at Gamma point, frequencies
are obtained by imposing acoustic sum rule at the Gamma point with
asr=simple.

Thank you!!


-- 
With regards
Anupriya Nyayban
Ph.D. Scholar
Department of Physics
NIT Silchar
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