[Pw_forum] Open shell system calculations

[stefano de gironcoli]

I think spin unpolarized calculations in that case miss a large exchange 
correlation contribution coming from spin alignment.
Isolated Mn2+ should have total magnetization equal to 5 (i think). You 
can set this from input. Or you can just let the code find the minimum 
by itself.

you can use martina-tuckerman option to decouple periodic images.
It's very important for charged systems.
That should reduce the size of supercell needed to have stable numbers.

stefano


On 10/08/2017 08:50, Iryna Zaporozhets wrote:
> I have a single Mn2+  ion in the isolated system with vacuum between 
> periodic images. Spin-unpolarized calculations run without any errors 
> so I wonder whether spin-unpolarized calculations produce any useful 
> results.
>
> Best, Iryna Zaporozhets
>
> 2017-08-09 23:39 GMT-07:00 stefano de gironcoli <degironc at sissa.it 
> <mailto:degironc at sissa.it>>:
>
>     depends on your system, is it magnetic ?
>     metallic aluminum or copper have spin compensated densities and
>     you can use nspin=1.
>     nickel or iron are magnetic and nspin=2 is needed.
>     stefano
>
>
>     On 10/08/2017 08:29, Iryna Zaporozhets wrote:
>>     Dear PW community,
>>
>>     I am working with an open-shell system which requires a lot of
>>     computational efforts. Is it possible to use other options than
>>     spin-polarized calculations (nspin = 2) to reduce computational
>>     cost, for example, restricted open-shell  DFT?  Is there any
>>     physical meaning to the results obtained with
>>     spin-unpolarized (nspin = 1) calculations in case of the
>>     open-shell system?
>>
>>     Thank you,
>>     Iryna Zaporozhets,
>>     Master student in Chemistry
>>     Kharkiv National University, Ukraine
>>
>>
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