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Re^2: s-squared

Masoud Nahali

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 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:


>>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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