Linear bends in Firefly (as well as in GAMESS (US)) are strange
and odd beasts. Generally, I would not recommend to use them.
Constructing good z-matrix for such degenerate and
pathological cases as this molecule is could be a bit tricky.
Attached please find the example of good coordinates.
On Sun Jul 10 '11 7:54am, Alexander V. Malutin wrote
>Hi. I'm constantly getting bored by strange problems with $LIBE group. Every time i try to optimize molecule with linear bended region in internal coordinates, geometry search is almost constantly failing to locate stationary point then i'm using OPTTOL=1d-5 or below. Visualization of search steps shows oscillatory behavior near linear bend geometry, so i'm pretty much convinced that using linear bend $LIBE group is essential. However then i do use it, it results in error on the first step:
> TRANSFORMING DISPLACEMENT FROM INTERNALS TO CARTESIANS
> THE ROOT MEAN SQUARE ERROR IN ITERATION 1 IS 0.00004979
> THE ROOT MEAN SQUARE ERROR IN ITERATION 2 IS 0.00006993
> THE ROOT MEAN SQUARE ERROR IN ITERATION 3 IS 0.00013865
> *** ROUNDOFF ERROR IN LIBE - TEST,DOTP= -0.2563072398E-06 -0.7003238419E-03
>How can i solve this problem? May be i am missing something and should supply input files with some special keys to avoid such errors? As far as i can see such errors have unpredictable character, sometimes $LIBE supported input works just fine, but very often run fails due this nasty roundoff problem, witch is extremely annoying. Will grateful for any help regarding this matter.
> $SYSTEM MEMORY=128000000 $END
> $CONTRL SCFTYP=MCSCF RUNTYP=OPTIMIZE $END
> $CONTRL UNITS=ANGS MULT=1 NZVAR=8 $END
> $BASIS GBASIS=N31 NGAUSS=6 NPFUNC=1 NFFUNC=1 $END
> $MCSCF CISTEP=GUGA FULLNR=.TRUE. FORS=.FALSE. $END
> $DRT GROUP=C1 SOCI=.TRUE. NMCC=5 NDOC=6 NVAL=3 NEXT=2 $END
> $STATPT NSTEP=100 OPTTOL=1d-6 HSSEND=.TRUE. $END
> $FORCE NVIB=2 VIBANL=.TRUE. PURIFY=.TRUE. TEMP(1)=0.001, 298.15, 398.15 $END
> $GUESS GUESS=MOREAD NORB=67 $END
> Cyanamide NH2-CN MCSCF.
> N 7.0 0.0000000000 0.0000000001 1.2870668159
> C 6.0 0.0000000001 0.0000000033 0.1424955716
> N 7.0 0.0000000000 -0.0000000042 -1.1681804833
> H 1.0 -0.0000000001 0.8498848363 -1.6742591359
> H 1.0 -0.0000000001 -0.8498848188 -1.6742591918
> $ZMAT IZMAT(1)=1,1,2, 1,2,3, 1,3,5, 1,3,4,
>2,2,3,5, 2,5,3,4, 3,2,3,4,5, 5,1,2,3 $END
> $LIBE APTS(1)=1.0,0.0,0.0 $END
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[ patho.rar ] Sample of good Z-matrix for Cyanamide