Subject: (summary) can CISD be tested by "stable" or "stable=opt" in Gaussian?

From: "Kiniu WONG Kin-Yiu" <[email-masked]>
Date: Mon, 25 Sep 2000 13:02:08 +0800

Dear all,

    Recently, I got the answer from the reply of official Gaussian Inc. .
Actually, once the HF wavefucntion is stabilised, then its corresponding CI
wavefunction should be stable also. So, now the question is just how we
could use the stabilised HF wavefunction to continue calculating CI energy.
Here is the reply from Gaussian:

> This job needs to be done in two steps:
>
> %chk=ozone
> #p UHF 6-31G(d) SCF=(Tight, direct) Stable=Opt MaxDisk=2GB
>
>  ozone CISD energy stable optimizaiton?
>
>   0 1
>  O
>  O                    1     1.272
>  O                    2     1.272    1     116.8
>
> --link1--
> %chk=ozone
> #p UCISD/6-31G(d) SCF=(Tight, direct) guess=read geom=allcheck
> symm=noscf
>
>
>
> Adding SYMM=NoSCF in the second step is critical, since it preserves the
> relaxing of the symmetry constraints, which is what STABLE=OPT did.
> Without it, you just get back the unoptimized wavefunction.
>
> --
> Joseph Ochterski, Ph.D
> Senior Customer Service Scientist
> [email-masked]
>

    Finally, I would like to thanks all who have replied me and concerning
this question! Thank you!

Regards,
Kiniu WONG Kin-Yiu
Undergraduate student
Department of Physics
The Chinese University of Hong Kong
Email: [email-masked]  or  [email-masked]