[CP2K-user] [CP2K:19159] When to use LSD option?

[Matt Watkins]

Hello,
the LSD (or UKS etc) allows the spin up and spin down orbitals to relax 
independently due to the different exchange interactions. There are other 
methods (ROKS for instance, though less often used) that allow open shell 
calculations without this extra freedom. 
So you need to specify the charge, the multiplicity and the method (LSD).  
This doesn't apply to metallic systems where you have smearing of electrons.
Matt

On Saturday, 29 July 2023 at 19:37:28 UTC+1 Niharendu Choudhury wrote:

> I am still confused. CHARGE and MULTIPLICITY KEYWORDS are not enough to 
> describe the unpaired electrons in the systems?
> Do I need to use SPIN_POLARIZED or UKS in addition to the above keywords? 
> What is the meaning of LSD then?
>
> @Prof. Hutter or any other developers please clarify.
>
> Cheers
> Niharendu Choudhury
>
> On Wed, Jul 26, 2023 at 7:21 PM Martin Konôpka <konop... at gmail.com> wrote:
>
>> Dear Nihar,
>>
>> I am not a CP2K expert but I guess you definitely should use either the 
>> LSD keyword or one of its synonyms (e.g. SPIN_POLARIZED or UKS or some 
>> further) in the calculations you mentioned. In cases when the number of 
>> electrons with spin up differs from the number with spin down, such an 
>> option is necessary in my knowledge. Even if some part of the calculations 
>> be for systems in a (globally) singlet state, I would apply spin 
>> polarisation for consistency between the systems under treatment.
>>
>> Best
>> Martin.
>>
>> st 26. 7. 2023 o 10:02 Niharendu Choudhury <nihar... at gmail.com> 
>> napísal(a):
>>
>>> Hi CP2K experts,
>>> I have a system in which a metal ion and water molecules are there.
>>> My metal ion has different oxidation states and accordingly different 
>>> number of unpaired electron/s (which gives me different multiplicity). So I 
>>> have CHARGE and MULTIPLICITY KEYWORDS to specify these two in the input 
>>> file. Then, should I use LSD, if MULTIPLICITY is not equal to one?
>>>
>>> Can anybody clarify it. 
>>>
>>> Regards
>>> Nihar
>>>
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> -- 
> ---------------------------------------------------------
> Dr. Niharendu Choudhury 
> Scientific Officer 
> Theoretical Chemistry Section
> Chemistry Group
> Bhabha Atomic Research Centre
> Mumbai- 400 085, India.
> ---------------------------------------------------------
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