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Re^3: About NSTATE, WSTATE and AVECOE in XMCQDPT2

Alex Granovsky
gran@classic.chem.msu.su


Hi,

by the way, we now have the code to perform xmcqdpt2 after
each optimization step of rsurface procedure. Are you interested?

Kind regards,
Alex


On Wed Oct 24 '12 7:41am, Panwang Zhou wrote
--------------------------------------------
>Dear Alex,

>Thanks for you comments.

>Best Regards,
>Panwang Zhou
>
>
>On Tue Oct 23 '12 8:48pm, Alex Granovsky wrote
>----------------------------------------------
>>Dear Panwang Zhou,

>>Sorry for some delay with my response.

>>Please see my comments below.
>>
>>
>>On Mon Oct 22 '12 7:55am, Panwang Zhou wrote
>>--------------------------------------------
>>>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.
>>
>>
>>That's correct. In addition, Firefly v. 8.0.0 includes
>>the possibility to filter triplets out but it's a different story

>>>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?

>>It is correct provided you put the converged MOs into the $vec group
>>of the input file and moread it using

>>

 $guess
  guess=moread norb=the_total_number_of_MOS
 $end

>>In addition, for better precision I'd suggest to use
>>

 $contrl wide=.t. $end

>>This will punch MOs with all significant digits.

>>Alternatively, you can set inorb to zero and perform MCSCF then
>>XMCQDPT2 computations using single input file.
>>
>>
>>>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)."

>>That's not always true i.e. quite often nstate=2 is enough.
>>However, unlike with other MS-MR-PT2 theories, with XMCQDPT2
>>you do can improve results increasing NSTATE.
>>
>>
>>>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.

>>Both WSTATE and AVECOE arrays are used to define the state's weights
>>used compute state-averaged density matrices. Technically, the
>>averaging used to define semi-canonical orbitals and to define
>>orbital energies of these orbitals, can be different. If both WSTATE
>>and AVECOE are given, the first one defines the averaging used to
>>compute orbitals while the second is used for energies. If only one
>>of them is given in input, then the second one will be set to that
>>provided in the input so that WSTATE and AVECOE will be identical.
>>The latter option should be used almost exclusively unless one has
>>really good reasons why to use different averaging for different
>>stages.  
>>
>>
>>Normally, for S0->S1 transitions one needs to average over S0 and S1
>>only and with equal weights i.e. to set WSTATE(1)=1,1,-0

>>>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.

>>Yes they can be used. They correspond exactly to the same overall
>>wavefunction but with different MOs and CI vector components.

>>>(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?

>>The only valid is the default i.e. inorb=0

>>>
>>>
>>>Best Regards,
>>>Panwang Zhou

>>>

>>Kind regards,
>>Alex Granovsky

>>


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