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Panwang Zhou
pwzhou@gmail.com

Recently, I performed a MCSCF(16,14) calculation then following a XMC-QDPT2 calculation on the constructed LIIC curve among the optimized cis-HBDI, CI and trans-HBDI structures, the obtained MCSCF curve is smooth and continuous whereas the obtained XMC-QDPT2 curve is  discontinuous at the CI point (see attachment). I'm not clear why the XMC-QDPT2 curve is discontinuous and how to resolve this problem?

The following is the part of input file:

$CONTRL SCFTYP=MCSCF RUNTYP=ENERGY EXETYP=RUN MAXIT=50 ICHARG=-1
   MULT=1 FSTINT=.T. GENCON=.T. INTTYP=HONDO NOSYM=1
   ICUT=11 ITOL=30 WIDE=.T. MPLEVL=2 $END
$SYSTEM MWORDS=480 TIMLIM=60000.0 KDIAG=0 NOJAC=100 $END
$SYSTEM MKLNP=1 NP=12 $END
$SMP SMPPAR=.T. HTTNP=1 $END
$SCF DIRSCF=.T. FDIFF=.F. NCONV=8 $END
$P2P P2P=.T. DLB=.T. $END
$TRANS MPTRAN=2 DIRTRF=.T. AOINTS=DIST ALTPAR=.T. MODE=112 $END
$MCSCF CISTEP=ALDET FULLNR=.F. SOSCF=.T. MAXIT=100 $END
$MCSCF IFORB=.T. $END
$DET NCORE=49 NACT=14 NELS=16 NSTATE=6 WSTATE(1)=1,1 DISTCI=12 $END
$XMCQDPT NSTATE=2 EDSHFT=0.02 THRGEN=1D-12 MXBASE=90 $END
$XMCQDPT HALLOC=.T. $END
$XMCQDPT IFORB(1)=-1,1,1 WSTATE(1)=1,1,-0 AVECOE(1)=1,1,-0 $END
$BASIS GBASIS=N31 NGAUSS=6 NDFUNC=1 NPFUNC=1 DIFFSP=.TRUE. $END
$GUESS GUESS=MOREAD NORB=359 $END
$MCQFIT $END

I have tried to increas the NSTATE in XMCQDPT group, however, the required memory is larger than 480 MWORDS, thus the calculation failed.

Best Regards!

Panwang Zhou

This message contains the 68 kb attachment [ LIIC_curves.zip ] MCSCF and XMC-QDPT2 Curves