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Re: Why is the multiplicity still equal to 1 when MULT=3 is set in a CASSCF calculation

Thomas
thomaspijper@hotmail.com

Dear Patrick,

MICIT is the amount of microiterations, so it is not related to the multiplicity. From the manual:

`MICIT = Maximum number of microiterations within a single MCSCF iteration. (default=5 for FOCAS or SOSCF, or 1 for FULLNR or QUAD)`

The multiplicity of each state is printed at the end of the CI computation. For example, the line

` STATE   1  ENERGY=       -37.6620071411  S=  1.00  SZ=  0.00  SPACE SYM=A   `

shows you that state 1 in this example is a triplet state (S=1.00). ALDET code always prints states of different multiplicity. Which states are used is printed near the line "THE DENSITIES ARE STATE AVERAGED OVER".

As to why your MCSCF convergence is problematic, it is always difficult to say without seeing the full output file. However, I do notice that you are not using the converged orbitals of an earlier run. With MCSCF, this is pretty much always necessary -- guessed orbitals are just not good enough to reach convergence. My advice is to do a Hartree-Fock calculation and use the converged orbitals as a start for the MCSCF convergence. Also, take time to carefully construct your active space, i.e. which orbitals should be in the active space and which not. Tips on this can be found in the manual.

Hope this helps.

Kind regards,
Thom

On Sun Nov 18 '12 4:31am, Patrick SK Pang wrote
-----------------------------------------------
>Dear all,

>I want to get the optimized geometry of the first triplet state.  MThe input file is as follows.

> \$CONTRL RUNTYP=Optimize \$END
> \$CONTRL SCFTYP=MCSCF INTTYP=HONDO \$END
> \$CONTRL ICHARG=0 MULT=3 \$END
> \$CONTRL NZVAR=33 \$END
> \$ZMAT DLC=.T. AUTO=.T. \$END
> \$BASIS GBASIS=N31 NGAUSS=6 \$END
> \$BASIS NDFUNC=1 NPFUNC=1 \$END
> \$BASIS DIFFSP=.TRUE. DIFFS=.TRUE. \$END
> \$MCSCF CISTEP=aldet MAXIT=2000 FULLNR=.T. \$END
> \$DET NCORE=19 NACT=10 NELS=10 NSTATE=2 \$END
> \$DET GROUP=C1 ITERMX=2000 \$END
> \$DET WSTATE(1)=0,1 \$END
> \$SYSTEM TIMLIM=10000 MWORDS=100 \$END
> \$P2P P2P=.T. DLB=.T. \$END
> \$STATPT NSTEP=200 \$END
> \$DATA
>Molecule specification
>C1
>...
>...
>...
> \$END

>However, the output file shows MICIT=1. Why?  AAlso, it appears that it is difficult to converge. How can I fix it?

>ITER �  TTOTAL ENERGY � � � �  DDEL(E) � LAG.ASYMM. SQCDF  MMICIT � DAMP
> � 1 � �-320.622290945 � �-320.622290945 �0.638832 1.703E-01 �1 � 0.0000
> � 2 � �-321.554042126 � � �-0.931751181 �0.310512 5.000E-01 �1 � 0.0000
> � 3 � �-321.428474924 � � � 0.125567202 �0.164635 5.000E-01 �1 � 2.2612
> � 4 � �-321.444397078 � � �-0.015922154 �0.113475 5.000E-01 �1 � 9.0449
> � 5 � �-321.446525949 � � �-0.002128871 �0.107891 5.000E-01 �1 � 0.5653
> � 6 � �-321.434785860 � � � 0.011740089 �0.158519 5.000E-01 �1 �36.1795
> � 7 � �-321.437384415 � � �-0.002598555 �0.116446 5.000E-01 �1 144.7178
> � 8 � �-321.438041052 � � �-0.000656638 �0.116559 5.000E-01 �1 � 9.2408
> � 9 � �-321.445631519 � � �-0.007590467 �0.117134 5.000E-01 �1 � 9.2408
> �10 � �-321.448360730 � � �-0.002729211 �0.117458 5.000E-01 �1 � 1.1947
> �11 � �-321.420594072 � � � 0.027766658 �0.237020 5.000E-01 �1 �76.4587
> �12 � �-321.421697453 � � �-0.001103381 �0.223346 5.000E-01 �1 305.8347
> �13 � �-321.421987863 � � �-0.000290410 �0.219965 5.000E-01 �1 �21.1864
>...
>...
>...
> 600 � �-321.458209353 � � � 0.000000000 �0.147571 5.000E-01 �1*********
> 601 � �-321.458209353 � � � 0.000000000 �0.147571 5.000E-01 �1*********
> 602 � �-321.458209353 � � � 0.000000000 �0.147571 5.000E-01 �1*********
> 603 � �-321.458209353 � � � 0.000000000 �0.147571 5.000E-01 �1*********
> 604 � �-321.458209353 � � � 0.000000000 �0.147571 5.000E-01 �1*********
> 605 � �-321.458209353 � � � 0.000000000 �0.147571 5.000E-01 �1*********
> 606 � �-321.458209353 � � � 0.000000000 �0.147571 5.000E-01 �1*********
> 607 � �-321.458209353 � � � 0.000000000 �0.147571 5.000E-01 �1*********
> 608 � �-321.458209353 � � � 0.000000000 �0.147571 5.000E-01 �1*********
> 609 � �-321.458209353 � � � 0.000000000 �0.147571 5.000E-01 �1*********
> 610 � �-321.458209353 � � � 0.000000000 �0.147571 5.000E-01 �1*********
> 611 � �-321.458209353 � � � 0.000000000 �0.147571 5.000E-01 �1*********
> 612 � �-321.458209353 � � � 0.000000000 �0.147571 5.000E-01 �1*********
>
>
>Regards,

>Patrick

Sun Nov 18 '12 3:44pm