[Pw_forum] noncolin variable for scalar relativistic pseudopotentials

[Lorenzo Paulatto]

You can use either, but you won't get much benefit from noncolin=.true. if
you don't use full relativistic pseudos. Also, noncolinear calculations are
more expensive, and some features are not implemented in this case.
On 4 Mar 2016 3:32 a.m., "Mingchao Wang" <wmc1406 at gmail.com> wrote:

> 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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>
>
>
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