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Re: IRC for MEP calculation

Alex Granovsky
gran@classic.chem.msu.su


Dear Alexandra,

could you please send me your exact input files off the list?
I'll try to help you.

Kind regards,
Alex Granovsky




On Thu Jun 25 '15 4:52am, alexandra wrote
-----------------------------------------
>Hello, Dr. Granovsky!

>I am very interested in reproducing results of the your paper (J. Chem. Theory Comput. 2013, 9, 4495−4506), but cannot overcome one problem.

>In the paper MEP (in CASSCF and CASPT2 level) is calculated in molcas, but I hope it is technically realizable in FF also.

>As far as I understand, GS2 method is not suitable as it requires exact Hessian, that hardly can be obtaited in SA-calculations. At first I tried GS2, but the direction if minimum imaginary mode of FC excited state is far from the expected direction, so IRC goes in undesirable way.

>Now I am trying RK4, but for PSB3 cation (from the paper) and analogous simple flat molecules MEP goes down with retaining the skeleton planarity and finally stops without changing the skeleton dihedral.

>Obviously it stops because of being trapped in the valley of PES. The problem is to force the molecule go in the direction of bond rotation. I tried a lot of trivial ways to solve this problem, here is my last input:

> $CONTRL SCFTYP=MCSCF RUNTYP=IRC ICHARG=+1 INTTYP=HONDO D5=1 ICUT=11
>ICHARG=+1 NZVAR=1 $END
> $ZMAT DLC=1 AUTO=1 $END
> $SCF DIRSCF=1
> $SYSTEM TIMLIM=300000 MWORDS=300 $END
> $BASIS GBASIS=n31 NGAUSS=6 NDFUNC=1 $END
> $GUESS GUESS=MOREAD NORB=89 $END
> $IRC PACE=RK4 SADDLE=0 STRIDE=0.05 NPOINT=300 $END
> $STATPT METHOD=GDIIS OPTTOL=1D-4 NSTEP=300 DXMAX=0.5 TRMIN=0.1 $END
> $DET CVGTOL=1D-8 NCORE=16 NACT=5 NELS=6 PURES=0 NSTATE=9
>WSTATE(1)=1,1,1 $END
> $MCSCF METHOD=DM2 ACURCY=1D-7 ENGTOL=1D-12 CISTEP=ALDET NTRACK=6 ISTATE=3 $END
> $TRANS CUTTRF=1D-13 $END
> $CIINP CASTRF=1 $END
> $DATA
>... molecule is almost the same, but instead of H2C=CH-CH=CH-CH=NH2+ it is H2N-CH=CH-CH=NH2+  
> $END
> $VEC
>...
> $END

>Could you, please, advice some tricks for solving this problem within FF?
>
>
>Regards,
>Alexandra


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