[Pw_forum] "relax" vs. "vc-relax" calculation

[Masoud Nahali]

Dear Tram

To specify how metallicity is treated you should use "smearing" and have to
determine degauss value (smearing width). These options not only use for
metallic systems but also for spin-polarized systems. If the mean of
Alessandra is performing a spin polarized calculation he should set nspin=2
and set a starting_magnetization otherwise his case is a metallic one !! . I
think you should plot E VS. degauss to find the convergence value of
degauss. About "Omega" (slide 11) I don't exactly know his mean. I hope it
is helpful.

Best Wishes

 Masoud



--------------
Masoud Nahali, Sharif University of Technology
masoud.nahali at gmail.com;
alum.sharif.edu/~m_nahali<http://alum.sharif.edu/%7Em_nahali>

P Save a Tree . . . Please don't print this e-mail unless you really need
to.

On Mon, Jul 11, 2011 at 5:57 AM, Tram wrote:

>
>
>  Dear Masoud,
>
>  Thank you for your information. The tutorial is also very helpful. I have
> some small questions related to the tutorial, I hope you don't mind. on the
> slide # 11, the author has used the "?" sign, and what does it represent?.
> also on the slide # 32, there is a warning sign saying "the total number of
> electron is odd", so the degauss value was marked very low, as 0.0037. So
> does it mean that the degauss should be low for odd number of electron and
> higher for even cases?
>
> I really appreciate your helps!
> Tram
>
>
> On Thu, Jul 7, 2011 at 2:32 AM, Masoud Nahali <masoudnahali at gmail.com
> >wrote:
>
> >
> >      Dear Tram
> >
> >          I think that vc-relax calculation is more convenient for your
> > case; in addition you should glance over the below tutorial about defects
> :
> >
> > http://www.fisica.uniud.it/~giannozz/QE-Tutorial/tutorial_defects.pdf
> >
> >          I hope it is useful.
> >
> >
> > Best Wishes
> >
> >  Masoud
> >
> >
> >
> > --------------
> > Masoud Nahali, Sharif University of Technology
> > masoud.nahali at gmail.com; alum.sharif.edu/~m_nahali<
> http://alum.sharif.edu/%7Em_nahali>
> >
> > P Please don't print this e-mail unless you really need to.
> >
> >
> > *Tram wrote on Thu Jul 7 06:47:35 CEST 2011*
> >>
> > Dear Everyone,
> >      I have a quick question regarding the "relax" vs. "vc-relax"
> > calculation for my SiC structure. As I run the " scf" calculation with a
> > single defect, e.g. interstitial or sustitutional, the lattice parameter
> of
> > the unit cell is expected to be stretched. And as I checked, the lattice
> > constant got larger when introduced defect. Now, I'm just wondering
> between
> > the "relax" calculation (which will only relax the atomic position ) and
> the
> > "vc-relax" one (which will relax both atomic position and the lattice of
> the
> > unit cell), which one would you recommend to use?
> >
> > Thank you very much,
> >
> > Tram Bui
> >
> > M.S. Materials Science & Engineering
> > trambui at u.boisestate.edu <
> http://www.democritos.it/mailman/listinfo/pw_forum>
> >
>
>
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