Ceilidh ... Problematic CASSCF convergence with higher states

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Problematic CASSCF convergence with higher states

Dear fellow Fireflyers,

I'm currently studying a photochemical electrocyclization reaction, using the CASSCF and XMCQDPT methods. Geometry optimizations and a relaxed PES scan of the ground state have already successfully given me the geometries of the reactant and the product (as well as the ground state transition state), so I’m now focusing on the first and second excited states.

A XMCQDPT calculation of the reactant geometry shows a big reordering of the states: the second and third XMCQDPT state are mainly formed by the seventh and eight CASSCF state.

EIGENVECTORS OF THE EFFECTIVE HAMILTONIAN

                      1          2          3   

               *********************************

    1            -0.996647   0.000661  -0.014560
    2            -0.046349   0.056924   0.286798
    3            -0.050143  -0.079306   0.127224
    4             0.006949   0.001413   0.017246
    5            -0.012656   0.043812  -0.068093
    6             0.001191   0.175646  -0.044638
    7            -0.000448   0.932143   0.006876
    8            -0.003086   0.016572  -0.929936

Consequently, I would like to investigate the PES of these roots. However, during geometry optimizations I’ve found the CASSCF convergence to be very problematic. There is a lot of reordering of states and after a 2-3 optimization steps the SCF will not converge anymore. These are the keywords that I use:

 $CONTRL SCFTYP=MCSCF RUNTYP=OPTIMIZE INTTYP=HONDO UNITS=ANGS
 FSTINT=.T. GENCON=.T. $END 
 
 $SYSTEM TIMLIM=10000 MWORDS=100 $END
 $SMP CALL64=.T. $END
 $P2P P2P=.T. DLB=.T. $END

 $BASIS GBASIS=N21 NGAUSS=3 $END

 $MCSCF CISTEP=GUGA MAXIT=400 ISTATE=3 NTRACK=10 $END
 $DRT GROUP=C1 FORS=.T. NMCC=104 NDOC=5 NVAL=5 $END
 $GUGDIA NSTATE=11 ITERMX=400 $END
 $GUGDM2 WSTATE(1)=1,1,0,0,0,0,1,1 $END

 $STATPT METHOD=GDIIS OPTTOL=0.00004 NSTEP=500 HESS=GUESS
 NPRT=-2 HSSEND=.F. $end
 
 $GUESS GUESS=MOREAD NORB=114 $END
 
! Speeding up the calculation
 $TRANS MPTRAN=2 DIRTRF=.T. AOINTS=DIST ALTPAR=.T. MODE=112 $end
 
! Extra accuracy
 $CONTRL icut=11 $END
 $moorth nostf=1 nozero=1 syms=1 symden=1 symvec=1 $END
 $GUGDIA cvgtol=1d-7 $END
 $trans cuttrf=1d-13 $END
 $mcscf acurcy=1d-7 ENGTOL=1.0d-12 $END

My question is if anyone has any suggestions for achieving better convergence on higher CASSCF states.

Thanks in advance!

Kind regards,
Thom

[ This message was edited on Fri Mar 18 '11 at 2:02pm by the author ]

Fri Mar 18 '11 2:02pm

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