CCL:G: problems in <S**2>

 Sent to CCL by: "Rajagopalan S." [r.subramanian()
 ipc.uni-stuttgart.de]
 Hi Brain, CJC,
Yes my complex is high spin tetranuclear Fe catalyst. So altogether 20 electrons (hence multiplicity of 21). 
 regards,
 raj
 Christopher Cramer cramer#%#umn.edu wrote:
 
 There is a curious bias for low spin amongst CCL readers.
Irrespective of whether Gaussian's FORMAT statement ever envisioned 3 digits to the left of the decimal place in S^2, a value of 110 is perfectly reasonable. It implies 20 unpaired electrons all high-spin coupled ( S^2 = S * (S + 1) = 10 * 11 = 110). This is a very nice single determinantal wave function and might be expected in the case of, say, a tetranuclear manganese complex having 4 ferromagnetically coupled d5 Mn ions.
Of course, the particular input deck of Raj S might indeed have an error, but there is nothing intrinsically wrong with the S^2 value. Instead, the formatting issue simply reflects what is likely to be some of the oldest (original?) code in Gaussian, written back in the day when small organic molecules where mostly the rule... Interestingly, the FORMAT used in the spin annihilation line is more flexible. 
 CJC
On Jun 2, 2008, at 6:25 PM, Brian Salter-Duke brian.james.duke[#]gmail.com wrote: 
 
 Sent to CCL by: Brian Salter-Duke [brian.james.duke]=[gmail.com]
 Raj S r.subramanian|,|ipc.uni-stuttgart.de wrote:
 
 Sent to CCL by: "Raj  S" [r.subramanian^ipc.uni-stuttgart.de]
 Dear ccl users,
I am using Gaussian03 package for optimization and freq. calculations. After opt. and freq. calculations i notice in the .log file the total spin <S**2> is marked ******. For e.g., look below 
 (A) (A) (A) (A)
 <S**2> of initial guess=*******
 Requested convergence on RMS density matrix=1.00D-08 within1000 cycles.
 Requested convergence on MAX density matrix=1.00D-06.
 Requested convergence on             energy=1.00D-06.
 No special actions if energy rises.
 Restarting incremental Fock formation.
 SCF Done:  E(UB+HF-LYP) =  -2934.91465147     A.U. after   20 cycles
             Convg  =    0.9816D-08             -V/T =  2.0810
             S**2   =  *******
 Annihilation of the first spin contaminant:
 S**2 before annihilation   110.0343,   after   110.0001
   1 Symmetry operations used in ECPInt.
 I dont know what is it *******?Is this some error...
It means the number is out of bounds of the format used to print. The problem is 110.0343 for S**2. This is way too high. What spin state do you have and what S**2 would you expect for a pure spin state (i.e. from ROHF not UHF)? 
 Brian.
 
 many thanks for your reply
 raja>> the strange characters on the top line to the === sign. You can
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 Rajagopalan Subramanian
 Universitaet Stuttgart, Zi-9.356, Pfaffenwaldring 55,
 D-70569 Stuttgart,                        Germany EU.
 tel. : +49 711 685 64464,    fax : +49 711 685 64443
 e-mail: r.subramanian{:}ipc.uni-stuttgart.de
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