[CP2K-user] [CP2K:14633] Re: Spin Contamination "Rule of Thumb?"

[Vladimir Rybkin]

Dear Stephen,

I would say S**2 is 6.150000 is fine. You should, nevertheless, whether 
your target properties look reasonable.

Yours,

Vladimir

понедельник, 25 января 2021 г. в 14:26:15 UTC+1, Stephen: 

> Hi  Vladimir, 
>
> Thanks for the response! What would you say about the difference in ideal 
> and single determinant spin states that are Delta_S**2 = ~0.1-0.2? I have a 
> few calculations where the ideal S**2 is 6.00000 and the single determinant 
> S**2 is 6.150000. 
>
> I found a rule for Gaussian calculations where the difference should be 
> less than 10% of the ideal S**2. However, is that a reasonable assertion 
> for all UKS DFT calculations? 
>
> With much appreciation, 
>
> Stephen 
>
> On Mon, Jan 25, 2021 at 6:50 AM Vladimir Rybkin <ry... at gmail.com> wrote:
>
>> Dear Stephen,
>>
>> the "cutoff" is what you find reasonable. To me, 12.019722 is practically 
>> no contamination, whereas delta=2.0 is a large one and the results are 
>> likely unreasonable. At least, you will not likely be able to get the 
>> latter published.
>>
>> Yours,
>>
>> Vladimir
>>
>> пятница, 22 января 2021 г. в 20:55:03 UTC+1, Stephen: 
>>
>>> Hi All, 
>>>
>>> I'm performing a few calculations of Ni(II) atom supported on a 
>>> metal-organic framework. The Ni(II) atoms can exhibit different spin 
>>> states, which means I must run UKS T while varying MULTI to account for all 
>>> the configurations. 
>>>
>>> Is there a specific rule for spin contamination when looking at the 
>>> S**2? For example, 
>>>
>>>   Ideal and single determinant S**2 :                   12.000000      
>>> 12.019722
>>>
>>> I've assumed that this particular structure has no spin contamination, I 
>>> have some other calculations where the difference between the ideal and 
>>> single determinant spin states is much larger (Delta_S**2 = ~2.00). 
>>>
>>> Does anyone have an appropriate cutoff for spin contamination? 
>>>
>>> With much appreciation, 
>>>
>>> Stephen 
>>>
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>
>
> -- 
> *Stephen P. Vicchio*
> PhD Candidate | Getman Research Group
> Dept. of Education GAANN Fellow
> Director of Student Organization Finances, Graduate Student Government
> Department of Chemical & Biomolecular Engineering 
> <https://www.clemson.edu/cecas/departments/chbe/>
> 105 Earle Hall | Clemson, SC 29634-0909
> s... at g.clemson.edu
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>
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