From owner-chemistry@ccl.net Wed May 16 08:36:00 2007
From: "Ulrike Salzner salzner*o*fen.bilkent.edu.tr" <owner-chemistry===server.ccl.net>
To: CCL
Subject: CCL:G: CASMP2 (G03)
Message-Id: <-34279-070516075901-2048-hSR9FmHwUsqA+kjotcm4pA===server.ccl.net>
X-Original-From: Ulrike Salzner <salzner**fen.bilkent.edu.tr>
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Date: Wed, 16 May 2007 14:58:37 +0300
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Sent to CCL by: Ulrike Salzner [salzner^^fen.bilkent.edu.tr]
Thanks John,
but you overlooked that it is a dication.
Regards,
Ulrike

John McKelvey jmmckel---gmail.com schrieb:
> Thiophene has 6 pi electrons, and I would assume that the bithiophene 
> you have has 12 pi electrons... This doesn't answer the CASMP2 issue, 
> however.
>
> John McKelvey
>
> On 5/15/07, *Ulrike Salzner salzner++fen.bilkent.edu.tr* 
> <owner-chemistry^ccl.net <mailto:owner-chemistry%5Eccl.net>> wrote:
>
>
>     Sent to CCL by: Ulrike Salzner [salzner^-^fen.bilkent.edu.tr
>     <http://fen.bilkent.edu.tr>]
>
>     Hello,
>     while trying to calculate the excitition energies of the bithiophene
>     dication with CASMP2 using Gaussian 03 I ran into the following
>     problem.
>     I am using all of the pi-electrons and pi-orbitals (10 electrons
>     and 10
>     orbitals). I got the ground and 5 excited states at the CASSCF level
>     without problems. Then I tried CASMP2 with the same active space.
>     First
>     there is a warning that there are more than 10000 configurations,
>     there
>     are actually about 63504. In the MP2 part all confuguratons are
>     skipped
>     and then it prints:
>     "Multireference MP2 with 0 configurations"
>     and the energy is same as without MP2. The same happens for ground and
>     first excited state. What is the problem? Is the active space too
>     large?
>     After reducing the active space to (8,8), MP2 runs using 21
>     configurations.
>     How are the configurations selected? How reliable is such a
>     result? Will
>     it use more configurations, if I reduce the active space further?
>     Thanks for assisstance,
>     Ulrike
>
>
>
>
>
>
>
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