Subject: PES Calculation

From: Lin Ping <[email-masked]>
Date: Mon, 05 May 1997 14:02:54 -0500

Hi ,everyone,

Does anyone have any suggestion about the calculation of potential
energy suface in the bond breaking process? I try to break the C-C
single bond in CH2CH-CN with geometry relaxation, I have tries quite
some methods such as UHF, CASSCF etc.. Also I have tried to put two
fragment( Optimized seperately) together and alter the orbital after a
triplet UHF calculation to make a singlet state and then decrease the
distance between the two carbon. In the casscf calculation I have
included 8 electrons and 10 orbitals to make sure to include the C-C
antibonding orbital. but None of this work properly. I think maybe it is
the delocalization make the calculation become difficult. By the way, I
am new in this area, so there are still a lot of things for me to learn.
Can you give me some suggestions or references in such a calculation? 

Also, when using 3-21G and LanL2DZ basis set to calculate a *MoH5
radical , it is unable to find a optimizated geometry and the SCF
calculation converged very slowly, especially when doing a DFT
calculation with LanL2DZ.

Thanks in advance.

LIN Ping
[email-masked]

-- 
Department of Chemistry           Phone No. : 409-862-9225
Texas A&M University              E-mail :  
College Station TX 77843-3255              [email-masked]
URL: http://http.tamu.edu/~p0l1112/

---

From: <[email-masked]>
Date: Mon, 5 May 1997 21:55:39 -0400 (EDT)

I am not sure about what is wrong with your results. If I
am doing this project about bond dissociation, I would:
1. starting from molecule, rather than fragments.
2. Keep the symmetry to be Cs in all calculations.
3. UHF would not work anyway. Minimum level should be Two-Configuration
SCF (TC-SCF),which is equvalent to GVB theory in Gaussain package. CASSCF
should also work, but it is hard to include all reqired orbitals.

=================================================================
Dr. Buyong Ma             [email-masked]
Computational Center for Molecular Structure and Design
Department of Chemistry
University of Georgia
Athens, Georgia 30602 USA            Voice (706) 542-2044
=================================================================

On Mon, 5 May 1997, Lin Ping wrote:

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