CCL:G: transition state searches with CASSCF ???

[errol lewars <elewars(a)trentu.ca>]

 Sent to CCL by: errol lewars [elewars-,-trentu.ca]
 2005 Nov 9
 Hello,
Yes, it is possible to find a TS at the CASSCF level with G03 (I used
 revision B.05); see J Phys Chem 2005, 109(43), 9827-9830. Start with a
 HF or MP2 structure, say, for the input geometry. Use corresponding MOs
 for the active space in comparing reactant, TS, and product.
However your reaction, in which closed-shell molecules are transformed
 into radicals may give special problems in calculating the activation
 energy.
 EL
 ====
 Theo de Bruin theodorus.de-bruin!^!ifp.fr wrote:
>  Sent to CCL by: "Theo de Bruin" [theodorus.de-bruin%a%ifp.fr]
> Hello
>  
>  I wish to know whether it is possible to perform transition state
>  searches at the CASSCF level of theory using Gaussian 03 rev C02. I asked the
>  same question to the helpdesk of Gaussian but I gave up, after waiting more than
>  5 weeks.
>  I would like to study a bi-molecular reaction in which two (neutral)
>  molecules are transformed into two radicals (reversed dismutation reaction).
>  Neither B3LYP nor X3LYP are capable to locate the TS, while
>  unrestricted MP2 gives the correct TS but unusual high barrier (delta H
>  activation) and delta H are obtained.
>  Thanks for sharing your thoughts how to handle this problem.
>  Kind regards,
>  Theo de Bruin
>  theodorus.de-bruin . ifp.fr>
>  
>