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Re^2: s-squared

Masoud Nahali
masoudnahali@gmail.com

Dear Professor Granovsky


Thanks for your attention. When the system is severely contaminated why the spins in x and y directions are changed and the Sz remains unchanged ?
In the case with s-squared = 5.1, can one report the result of the calculation as a proper local minimum with "3" multiplicity (let us suppose that there is not any imaginary frequency) or the spin was changed and the system seems to be a meta-stable ?
The SCF convergence of ROHF method is worse than the UHF and sometimes the ROHF SCF procedure never converge.        

Best Wishes
Masoud
--------------
Masoud Nahali, Sharif University of Technology


On Sat Feb 26 '11 1:19pm, Alex Granovsky wrote
----------------------------------------------
>Dear Masoud,

>s-squared is the expectation value of S2 operator:

>S2=Sx2+Sy2+Sz2

>>Spin Sz =1.0
>>s-squared = 5.1
>This means that this particular UHF wavefunction is severely
>contaminated by higher spin multiplicities as for pure-spin
>wavefunction one would get s-squared (high-spin case) = Sz*(Sz+1) = 1*(1+1) = 2
>You can try to use ROHF as it always gives pure-spin answers.

>Kind regards,
>Alex Granovsky
>
>
>
>On Thu Feb 24 '11 11:55pm, Masoud Nahali wrote
>----------------------------------------------
>>Dear Firefly Users
>>
>>
>>In ROHF and UHF calculations Firefly writes s-squared in the output file. If the meaning of the s-squared is
>>the mean of squared spin value (s**2), please let me know that the "s" represents the total spin angular momentum or not ? or in other words I want to know that Firefly takes into account the spin in x and y directions or not ? Also for instance, I have run a job which its MUL is equal to 3 and in the output file I have found :

>>Spin Sz =1.0
>>s-squared = 5.1

>>certainly the Sz=1.0 seems to be correct but the s-squared value is unclear for me ! I appreciate your help in advance to understand it.
>>
>>
>> Best Wishes

>> Masoud
>>--------------
>>Masoud Nahali, Sharif University of Technology        
>>  

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