[Pw_forum] noncolin variable for scalar relativistic pseudopotentials

[Mingchao Wang]

Dear Dr. Clavijo,

Thank you for your helpful information. My concern is about the setting of
noncolin variable. My question is: If I use scalar-relativistic
pseudopotentials for all atoms of CH3NH3PbI3, should I use noncolin=.TRUE
or noncolin=.FALSE? Now I am not quite whether scalar-relativistic
pseudopotentials directly include the nonlinear calculation.

Regards,

MC Wang

On Thu, Mar 3, 2016 at 8:42 PM, Josue Itsman Clavijo Penagos <
jiclavijop at unal.edu.co> wrote:

> Dear Mingchao Wang, as far as i know, the best case is to use
> Pseudopotentials of the same kind for all atoms, and preferably
> full-relativistic, so the spin-orbit coupling can be accurately taken into
> account, since it its known that Eg calculated without relativistic
> spin-orbit coupling is , although not very different that the
> no-relativistic calculated one due to cancelling over- and under-
> estimation issues in non-relativistic pseudopotentials, not a good obtained
> one. Long words short: you're getting a Eg value from a not so much
> physically accurate calculation framework.
>
> On the other hand, you not need to use H atoms to calculate Band
> Structure, since their contribution is only in the deep levels of valence
> and conduction bands (not near the band gap), unless you are into studying
> deep band structure actually.
>
> Finalliy, I think that noncolin=true is a must for spin-orbit calculations
> in pw.x , but i'm not 100% sure if that's true for an hybrid
> inorganic-organic system such as a CH3NH3PbI3 unit cell crystal at any
> temperature and crystal system of those this material can form.
>
> Anyway, Would you mind to put your pw input file, so i can compare my
> calculations with yours, since i'm currently working on the same system?
> that would be very very helpful to me and for others fellows in the forum
> and all would help you more and better, also.
>
> Best regards,
>
> Josué Clavijo, PhD.
> Assistant Professor
> Universidad Nacional de Colombia
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