CCL:G: Problem about calculation on the open-shell singlet in Gaussian.

[Grant Hill <jghill#wsu.edu>]

 Sent to CCL by: Grant Hill [jghill ~ wsu.edu]
One way forward would be to specify some sort of guess wavefunction,
 but I'm unsure of how to do this with Gaussian. You could try
 Guess=Mix. This mixes the HOMO and LUMO, destroys spatial symmetry and
 thus tries to prevent collapse to a restricted solution.
Reading the Guess entry in the Gaussian manual may provide further
 clues. You may also want to consider the symmetry of your wavefunction.
 HTH,
 Grant
 On 10 Jul 2009, at 10:40, Huo-Lei Peng huolei.peng166|-|gmail.com wrote:
> Thanks for your reply. I'd like to do calculation on
>  the open-shell
>  singlet (not a triplet). Open-shell(U) and restricted (R)
>  calculations in Gaussian gave me same results. So in Gaussian, how
>  to set input to make two electrons in two different orbitals but we
>  still have a singlet state?
>  Thanks.
>  Peng
> On Fri, Jul 10, 2009 at 11:14 AM, Jose Alberto Fernandes
>  jafernandes{:}ua.pt <owner-chemistry**ccl.net> wrote:
>  Sent to CCL by: "Jose Alberto Fernandes" [jafernandes=-=ua.pt]
>  Hello
>  I don't know if I understood your problem. Lets try.
>  Please see the following excerpt this input:
>  # rb3lyp/3-21g guess=check
> The "r" before "b3lyp" means that you want a close
>  shell
>  calculation. If you don't want electron pairing you have to put
>  "ub3lyp" instead of "rb3lyp".
> You should remember that a closed shell compound has always a
>  spin=1, and in a open shell the spin is different from 1. In the
>  case of nitrene (R-N ?) you can have R-N paired (spin=1) and
>  unpaired (spin=3).
>  So in the case of pairing you shoul input:
>  ------------------------
>  # rb3lyp/3-21g guess=check
>  comment
>  0 1
>  geometry
>  ----------------------
>  If you want unpairing you should input:
>  ---------------------
>  # ub3lyp/3-21g guess=check
>  comment
>  0 3
>  geometry
>  ----------------------
>  If I haven't answered your question, please explain better.
>  Best regards
>  Jose
>  > "Huo-Lei Peng huolei.peng166(!)gmail.com"  wrote:
>  >
>  > Sent to CCL by: Huo-Lei Peng [huolei.peng166]=[gmail.com]
>  > --001636c5a4fb6b291a046e527474
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>  >
>  > Hi, Dear All:
>  > I have a question about calculation on the open-shell singlet using
> > Gaussian. For example, nitrene species may have an open-shell and
>  closed
>  > shell singlets. In Gaussian, how to set the calculation to get
>  open-shell or
>  > closed-shell specifically? Thanks.
>  >
>  > Peng
>  >
>  > --001636c5a4fb6b291a046e527474
>  > Content-Type: text/html; charset=ISO-8859-1
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>  >
> > Hi, Dear All:<div><br></div><div>I have a
>  question about
>  calculation on the=
>  >  open-shell singlet using Gaussian. For example, nitrene species
>  may have a=
>  > n open-shell and closed shell singlets. In Gaussian, how to set
>  the calcula=
>  > tion to get open-shell or closed-shell specifically? Thanks.</div>
>  > <div><br></div><div>Peng</div>
>  >
>  > --001636c5a4fb6b291a046e527474--
>  >
>  >
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