[Pw_forum] negative frequency in high q-mesh

Lorenzo Paulatto lorenzo.paulatto at impmc.upmc.fr
Thu Jan 31 10:55:22 CET 2013

On 31 January 2013 08:32, Wei-Bing Zhang <weibingzhangavh at gmail.com> wrote:

> (i.e vc-relax directly and
> atomic relaxation with different lattice parameters).

Dear Wei,
please triple-check that you are doing everything correctly:
* that after the relax you are putting back the final parameters in the pw
* that in the SCF calculation that precedes the phonon one, forces and
stress are actually zero

I would also suggest to NOT play to input parameters: you are using
input_dft and exx_div_threatement both of which do not apply in your case.
Finally, ecutwfc = 65 is incredibly high for a Si ultrasoft
pseudopotential. Try to read something about this subject i.e. here <
(the "dual" is ecutrho/ecutwfc)


Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
phone: +33 (0)1 44275 084 / skype: paulatz
www:   http://www-int.impmc.upmc.fr/~paulatto/
mail:  23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05
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