You already solved the "issue": the variable-cell optimization is done with the plane-wave basis set for the starting cell, while the last step is done with the plane-wave basis set for the final cell. The two differ by a little bit (unless the cutoff is so high to guarantee perfect convergence in both cases). Search for "Pulay stress"in the literature.
Paolo On Wed, Sep 28, 2016 at 9:42 AM, Subhodip Chatterjee <[email protected]> wrote: > Dear Paolo, > > I want to add few more informations. > > After the vc-relax calculation, the magnitude of pressure is -*0.02 kbar* > . > > And what I mentioned in my last post (i.e. *3.61 kbar*) is the pressure > after the final SCF calculation. > > It will be a big help if you can guide me to solve this issue. > > Best regards > Subhodip > > On Mon, Sep 26, 2016 at 11:24 AM, Subhodip Chatterjee <[email protected] > > wrote: > >> INPUT >> >> *press = 0.001* >> *press_conv_thr = 0.0001* >> >> OUTPUT >> *P (kbar) = 3.61* >> >> Best regards >> Subhodip >> >> On Sat, Sep 24, 2016 at 7:15 PM, Paolo Giannozzi <[email protected]> >> wrote: >> >>> "A lot" = how much? the default tolerance on pressure convergence is 0.5 >>> KBar >>> >>> >>> Paolo >>> >>> On Sat, Sep 24, 2016 at 8:39 AM, Subhodip Chatterjee < >>> [email protected]> wrote: >>> >>>> Dear PWSCF developers, >>>> >>>> Is there any restriction in the code for the "press" (target pressure) >>>> input? >>>> >>>> I successfully get my vc-relax calculations converged to desired >>>> pressure values as high as several terapascal, however, when I set a low >>>> enough value, e.g. 1 bar (i.e. press = 0.001), the final pressure in the >>>> output differs a lot! >>>> >>>> Best regards >>>> Subhodip >>>> >>>> -- >>>> *Subhodip Chatterjee* >>>> >>>> *Senior Research Fellow* >>>> >>>> *Department of Chemistry* >>>> *University of Calcutta* >>>> *Kolkata, India* >>>> >>>> _______________________________________________ >>>> Pw_forum mailing list >>>> [email protected] >>>> http://pwscf.org/mailman/listinfo/pw_forum >>>> >>> >>> >>> >>> -- >>> 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 >>> >>> >>> _______________________________________________ >>> Pw_forum mailing list >>> [email protected] >>> http://pwscf.org/mailman/listinfo/pw_forum >>> >> >> >> >> -- >> *Subhodip Chatterjee* >> >> *Senior Research Fellow* >> >> *Department of Chemistry* >> *University of Calcutta* >> *Kolkata, India* >> > > > > -- > *Subhodip Chatterjee* > > *Senior Research Fellow* > > *Department of Chemistry* > *University of Calcutta* > *Kolkata, India* > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum > -- 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
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