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Raman calculations: FIELD-FREE SCF CALCULATION DID NOT CONVERGE

Vitaly
korepanov@nctu.edu.tw


Dear colleagues,
I am trying to calculate the Raman spectra of organic cation, and experience some problems.
The geometry optimization was OK, the Hessian also. But when I try to calculate Raman spectrum, I get the error "FIELD-FREE SCF CALCULATION DID NOT CONVERGE". I know what the manual says about it:
"Finite field calculations require large basis sets, and extraordinary accuracy in the wavefunction. To converge the SCF to many digits is sometimes problematic, but we suggest you use the input to increase integral accuracy and wavefunction convergence, for example
$CONTRL ICUT=20 ITOL=30 INTTYP=HONDO $END
$SCF NCONV=10 FDIFF=.FALSE. $END"
But it doen't help. I tried
1) TZV basis with 2p, d, f and two diffsp=1 diffs=1
2) aug-ccpvtz (external)
3) Sadlej pvtz (external)
with hybrid functionals (MPW1PW91 and B3LYP).
Nothing works.

Did anyone face such problems? Are there any hints to get over this?

V.


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