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CASSCF/MCQDPT input files questions

Thomas
thomaspijper@hotmail.com


Dear fellow Firefly users,

I’m quite new to Firefly and am currently learning how to properly do CASSCF and MCQDPT calculations. I’ve studied a number of example input files in order to learn which keywords are important for these types of calculations, but this has raised a few questions which I, so far, have been unable to find an answer to. Specifically, I have a hard time understanding what some of the groups/keywords in the MCQDPT2/retinal benchmark are for. This is what the input file of this benchmark looks like.


$contrl icharg=1 scftyp=mcscf d5=.t. icut=10 inttyp=hondo mplevl=2
exetyp=timing $end
$system mwords=200 timlim=100000 mklnp=4 $end
$smp csmtx=.t. $end
$guess guess=moread norb=540 kdiag=0 $end
$trans dirtrf=.t. mptran=2 mode=112 $end                                      
$mcscf maxit=100 cistep=aldet $end
$drt group=c1 fors=.t. nmcc=88 ndoc=6 nval=6 $end
$det group=c1 ncore=88 nact=12 nels=12 nstate=3 wstate(1)=1,1 $end
$gugem pack2=1 $end
$gugdm2 wstate(1)=1.,1. $end
$gugdia nstate=2 $end
$mcqdpt nstate=2 edshft=0.02 irot=1 thrgen=1d-12 $end


My questions are the following:

1- What is the function of the $DRT group in the above input file? As far as I understand, the CISTEP=ALDET keyword should make the program use the Ames Lab determinant CI and read the settings in the $DET group. Doesn’t this make the $DRT group (as well as the associated $GUGEM, $GUGDM2, and $GUGDIA groups) nonfunctional?

2- What is the function of the NSTATE keyword in the $MCQDPT group and what is its relation to the KSTATE keyword? At first glance, it seems that NSTATE is for the inclusion of more than one state in the MCQDPT part of the calculation, but I thought that this is what KSTATE is for. Incidentally, I have performed a few MCQDPT2 calculations with either keyword (NSTATE=2 or KSTATE(1)=1,1), but the differences in energy where negligible.

3- And finally, what does the IROT keyword in the $MCQDPT group do? Its function unfortunately is not described in the most up-to-date Firefly documentation as well as the current GAMESS US documentation.


I would be very thankful if someone could shine some light on these topics. Many thanks in advance.


Kind regards,
Thom

[ This message was edited on Mon Oct 18 '10 at 3:03pm by the author ]


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