From owner-chemistry&$at$&ccl.net Mon Sep 25 21:34:00 2006 From: "Gustavo Seabra gustavo.seabra**gmail.com" To: CCL Subject: CCL:G: HOMO-LUMO energy gap for cation radical Message-Id: <-32618-060925213245-27962-VO93Z7Jiio7C5EJeiE7kTQ() server.ccl.net> X-Original-From: "Gustavo Seabra" Content-Disposition: inline Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1; format=flowed Date: Mon, 25 Sep 2006 21:32:42 -0400 MIME-Version: 1.0 Sent to CCL by: "Gustavo Seabra" [gustavo.seabra*|*gmail.com] Hi, Here's my best guess: Unless you specify it, Gaussian will consider that you are asking for a closed shell, restricted calculation. However, in the radical case, Gaussian recognizes it as open-shell, and automatically turns on the unrestricted calculation, just for this one. (Gaussian has no idea that you intend to compare these results with closed-shell calculations...) So, in the end, you actually have calculatios using two different methods. I suggest that you run all calculations specifying an unrestricted hamiltonian. You can probably do that by specifying UB3LYP in Gaussian. HTH. Gustavo. On 9/25/06, Agalya agalya81_+_gmail.com wrote: > Sent to CCL by: Agalya [agalya81]![gmail.com] > ------=_Part_31934_13163170.1159205233650 > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > Content-Transfer-Encoding: 7bit > Content-Disposition: inline > > Dear Gustavo, > > I used b3lyp/6-31g* keywords > > I dint specify UHF or UMP2 in my calculation. I dint specify any keywords > for unrestricted calculation. > > With Regards, > Agalya > > > On 9/26/06, Gustavo Seabra gustavo.seabra * gmail.com < > owner-chemistry..ccl.net> wrote: > > > > Sent to CCL by: "Gustavo Seabra" [gustavo.seabra::gmail.com] > > Hi Agalya, > > > > How did you run those calculations? (keywords?) Are you explictly > > asking for unrestricted calculations for all systems? (UHF, UMP2, > > etc.) > > > > Gustavo. > > > > On 9/24/06, Agalya G agalya81,+,gmail.com > > wrote: > > > Sent to CCL by: "Agalya G" [agalya81#%#gmail.com] > > > Dear CCL users, > > > > > > In my previous message i made typing mistakes. > > > > > > Kindly answer for this question. > > > > > > I have a querry regarding HOMO-LUMO gap for cation radical system. > > > > > > I have performed calculations for neutral, cation radical and dication > > systems. > > > > > > 1) For neutral system, I used ( Charge=0 and spin multiplicity=1) > > > > > > 2) For cation radical system, I used ( Charge=+1 and spin > > multiplicity=2) > > > > > > 3) For dication, I used (charge=+2 and spin multiplicity=1) > > > > > > For neutal and dication systems, in gaussian03 program, it gives > > Occupied and Virtual orbital energies with alpha spin. > > > > > > For cation radical system, it gives occupied and unoccupied orbital > > energies for both alpha and beta spins. > > > > > > My querry is, how to compare HOMO-LUMO energy gaps between these > > systems. > > > > > > How to get HOMO-LUMO gap for cation radical system, in case i want to > > compare this value with HOMO-LUMO energy gap with neutral and dication > > systems. > > > > > > Kindly give me some suggestions. > > > > > > With Regards, > > > Agalya> > > > > > > > > ------=_Part_31934_13163170.1159205233650 > Content-Type: text/html; charset=ISO-8859-1 > Content-Transfer-Encoding: 7bit > Content-Disposition: inline > >
Dear Gustavo,
>
 
>
I used b3lyp/6-31g* keywords
>
 
>
I dint specify UHF or UMP2 in my calculation. I dint specify any keywords for unrestricted calculation. 
>
 
>
 With Regards,
>
Agalya

 
>
On 9/26/06, Gustavo Seabra gustavo.seabra * gmail.com <owner-chemistry..ccl.net > > wrote: >
Sent to CCL by: "Gustavo Seabra" [gustavo.seabra::gmail.com]
Hi Agalya,

How did you run those calculations? (keywords?) Are you explictly >
asking for unrestricted calculations for all systems? (UHF, UMP2,
etc.)

Gustavo.

On 9/24/06, Agalya G agalya81,+,gmail.com <owner-chemistry|a|ccl.net> wrote:
> Sent to CCL by: "Agalya  G" [agalya81#%#gmail.com] >
> Dear CCL users,
>
> In my previous message i made typing mistakes.
>
> Kindly answer for this question.
>
> I have a querry regarding HOMO-LUMO gap for cation radical system.
> >
> I have performed calculations for neutral, cation radical and dication systems.
>
> 1) For neutral system, I used ( Charge=0 and spin multiplicity=1)
>
> 2) For cation radical system, I used ( Charge=+1 and spin multiplicity=2) >
>
> 3) For dication, I used (charge=+2 and spin multiplicity=1)
>
> For neutal and dication systems, in gaussian03 program, it gives Occupied and Virtual orbital energies with alpha spin.
>
> > For cation radical system, it gives occupied and unoccupied orbital energies for both alpha and beta spins.
>
> My querry is, how to compare HOMO-LUMO energy gaps between these systems.
>
> How to get HOMO-LUMO gap for cation radical system, in case i want to compare this value with HOMO-LUMO energy gap with neutral and dication systems. >
>
> Kindly give me some suggestions.
>
> With Regards,
> Agalya



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