[QE-users] Phonon calculation not converging with vdw-df2-b86r

[Michele Re Fiorentin]

Dear QE developers and users,

I’m currently trying to compute the phonon dispersion of a 2d material with the vdw-df2-b86r functional. I have fully relaxed the structure and made sure that it is indeed a semiconductor (PBE gap > 3eV). However, the Electric Field Calculation by ph.x does not reach convergence in 100 iterations.

I’ve tried by varying alpha_mix (from 0.7 down to 0.2) and the nmix_ph (up to 20) parameters,  but it didn’t solve my issue. I’m using norm conserving pseudos from pseudo-dojo. If the calculations are carried out without the vdW functional (i.e. plain PBE) the same calculation converges very quickly without any problem.
Am I possibly missing something? Any help would be appreciated!
Best,


Michele


--
Michele Re Fiorentin, PhD

Department of Applied Science and Technology (DISAT)
Politecnico di Torino
corso Duca degli Abruzzi 24, 10129 Torino (Italy)
tel: +39 0110904333


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