## Firefly and PC GAMESS-related discussion club

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** About NSTATE, WSTATE and AVECOE in XMCQDPT2 **
Panwang Zhou

pwzhou@gmail.com

Dear Alex,I want to calculate vertical excitation energy between the ground state and the first excited state with XMCQDPT2, first I do a state-averaged MCSCF on the optimized S0 geometries, with the following settings:

$MCSCF CISTEP=ALDET FULLNR=.F. SOSCF=.T. MAXIT=100 $END

$DET NCORE=72 NACT=12 NELS=12 NSTATE=6 WSTATE(1)=1,1 $END

From this discussion club and the GAMESS-US manual I understand why the NSTATE should be larger than 2 as determinants do not correspond to any spin number and the triplet will also be obtained when the CISTEP=ALDET. The WSTATE(1)=1,1 will exclude the triplet and only do averaging on the first and second singlet.

Then I using the optimized MCSCF MOs to do the XMCQDPT2 calculation with the following settings:

$MCSCF CISTEP=ALDET FULLNR=.F. SOSCF=.T. MAXIT=100 $END

$DET NCORE=72 NACT=12 NELS=12 NSTATE=6 WSTATE(1)=1,1 $END

$XMCQDPT NSTATE=10 EDSHFT=0.02 THRGEN=1D-12 INORB=2 $END

$XMCQDPT WSTATE(1)=1,1,-0 AVECOE(1)=1,1,-0 $END

Is this correct for calculating the vertical excitation energy between S0 and S1?

I set NSTATE=10 because sanya has said "The size of the effective Hamiltonian given by NSTATE has serious effect on the transition energy (the energy grows with NSTATE and levels off at NSTATE~10)."

However, I'm not clear the relation between the NSTATE, WSTATE and AVECOE in XMCQDPT2, could you comment on this? In the firefly manual I could not find the explain for WSTATE

in XMCQDPT.

Additional two small questions:

From this dicussion club I know there are two ways to avoid CASCI integral transformation step in XMCQDPT calculation.

(1) First do the MCSCF calculation with the following settings:

$mcscf iforb=.t. sd=.t. $end

$contrl wide=.t. $end

The do the XMCQDPT with:

$guess guess=moread norb=the_overall_number_of_mos $end

$xmcqdpt inorb=2 iforb=0 $end

My question is: when the iforb is true in $mcscf, can the obained MOs be used for next MCSCF calculation, where the geometry is close to the previous one.

(2) Do the XMCQDPT wih the following settings:

$mcscf iforb=.t. $end

$xmcqdpt iforb(1)=-1,1,1 $end

My question is: what is the value should be set for inorb in this condition?

Best Regards,

Panwang Zhou

Mon Oct 22 '12 7:55am

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