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Alex Granovsky
gran@classic.chem.msu.su

I think there is no any reason to believe that binding energy must always be positive...

What are the absolute values of binding energies at d=2.319 and d=6.802 A? And what was the exact procedure to compute them?

regards,
Alex Granovsky


On Mon Nov 2 '09 9:26am, JIA HUO wrote
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>Dear Firefly users,

>Recently I used Firefly to calculate the binding energy between H2 and Cu cluster.
>The binding energy is normal (negative indicating attraction) for the equilibrium state. However, when increased the distance far away from equilibrium state (d=6.802 A; and d=2.319 for equilibrium state), the binding energy was positive (indicating repelling), but not approached zero.

>The input file is:
>! ?File created by MacMolPlt 7.3
> $CONTRL SCFTYP=UHF MPLEVL=2 maxit=100 runtyp=energy inttyp=hondo $END
> $CONTRL ICHARG=0 MULT=3 $END
> $MP2 METHOD=1 $END
> $p2p p2p=.t. xdlb=.t. $end
> $SYSTEM TIMLIM=100000 MEMORY=100000000 $END
> $BASIS  EXTFIL=.T. GBASIS=cct $END
> $SCF ? DIRSCF=.True. $END
> $GUESS  GUESS=HUCKEL KDIAG=0 $END
> $STATPT NSTEP=100 $END
> $DATA
>UHF/MP2/cct//UHF/X3LYP/TZVPP d=6.802A
>C1
>O ??8.0 ??4.23880 ??3.58020 ??1.18780
>O ??8.0 ??4.16780 ??0.80070 ??1.26460
>C ??6.0 ??4.65950 ??3.99360 ??2.29700
>H ??1.0 ??5.45520 ??4.74860 ??2.26030
>O ??8.0 ??1.45860 ??3.65150 ??1.22080
>O ??8.0 ??1.38850 ??0.87280 ??1.29950
>C ??6.0 ??1.09350 ??4.08950 ??2.34030
>H ??1.0 ??0.33830 ??4.88570 ??2.32420
>O ??8.0 ??4.20140 ??0.86020 ??3.51930
>O ??8.0 ??4.27810 ??3.64620 ??3.44230
>C ??6.0 ??4.56510 ??0.42910 ??2.39700
>H ??1.0 ??5.32000 ??9.63250 ??2.40630
>O ??8.0 ??1.41060 ??0.93880 ??3.55410
>O ??8.0 ??1.48950 ??3.72490 ??3.47520
>C ??6.0 ??0.99800 ??0.52570 ??2.44190
>H ??1.0 ??0.20150 ??9.77130 ??2.47120
>Cu ??9.0 ??2.81190 ??2.22280 ??1.11440
>Cu ??9.0 ??2.84720 ??2.29700 ??3.66570
>H ??1.0 ??2.54710 ??2.44020 ??0.46590
>H ??1.0 ??3.29420 ??2.46990 ??0.46550
> $END

>The output file is enclosed in the attachment