From chemistry-request@server.ccl.net Tue Dec 29 11:13:49 1998 Received: from www.ccl.net (www.ccl.net [192.148.249.5]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id LAA14268 for ; Tue, 29 Dec 1998 11:13:48 -0500 Received: from stark.udg.es (stark.udg.es [130.206.128.61]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with SMTP id LAA00078 Tue, 29 Dec 1998 11:08:09 -0500 (EST) Received: from stark.udg.es (cactus.udg.es [130.206.128.70]) by stark.udg.es (950413.SGI.8.6.12/950213.SGI.AUTOCF) via ESMTP id RAA23635 for ; Tue, 29 Dec 1998 17:10:11 -0200 Message-ID: <3688FF23.E5649CE7@stark.udg.es> Date: Tue, 29 Dec 1998 17:11:15 +0100 From: "Marta Forés i Bocsh" X-Mailer: Mozilla 4.04 [ca] (Win95; I) MIME-Version: 1.0 To: Lista de Quimica Subject: Description of the np* excited state with unrestricted methods Content-Type: multipart/alternative; boundary="------------928F57D8CF2BA81E31873B91" --------------928F57D8CF2BA81E31873B91 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Dear all, We are studying the first singlet excited state np* of 1-amino-3-propenal, which results of transferring an electron from the highest sigma occupied orbital to the lowest p virtual orbital. The UHF and UDFT methods can not describe this state well because these methods are based on a single determinant, which is a mixture of a singlet and a triplet state. The ROHF method could be a good solution to solve this problem. I would like to know if it is possible to use ROHF in Gaussian to study the 1np* state of 1-amino-3-propenal (the first singlet excited state of different symmetry from that of the ground state)? Others approximations to remedy the spin contamination problem could be the spin projection of the specific method or the “Sum method”. Does anybody know which can be the best approach or have some references about this question? The UMP2, UQCISD and UCCSD(T) wave functions are not described by only a single determinant, however, they are described assuming that the zeroth-order wave function is a single determinant. Can one consider in these methods that although the wave function is not spin-adapted they describe correctly the singlet open-shell np excited state of 1-amino-3-propenal? According to the Gaussian User’s Reference, with the “qcisd=s2t” keyword one can get the S2 value for this method, however, when I try to do it I obtain the following error: QPERR --- A SYNTAX ERROR WAS DETECTED IN THE INPUT LINE. #QCISD=S2T ' Last state="PRC1" TCursr= 4980 LCursr= 7 Error termination via Lnk1e in /soft/g94/l1.exe. Does anybody know which is the mistake I do? Thanks in advance. Marta --------------928F57D8CF2BA81E31873B91 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Dear all,

We are studying the first singlet excited state np* of 1-amino-3-propenal, which results of transferring an electron from the highest sigma occupied orbital to the lowest p virtual orbital. The UHF and UDFT methods can not describe this state well because these methods are based on a single determinant, which is a mixture of a singlet and a triplet state. The ROHF method could be a good solution to solve this problem. I would like to know if it is possible to use ROHF in Gaussian to study the 1np* state of 1-amino-3-propenal (the first singlet excited state of different symmetry from that of the ground state)? Others approximations to remedy the spin contamination problem could be the spin projection of the specific method or the “Sum method”. Does anybody know which can be the best approach or have some references about this question?

The UMP2, UQCISD and UCCSD(T) wave functions are not described by only a single determinant, however, they are described assuming that the zeroth-order wave function is a single determinant. Can one consider in these methods that although the wave function is not spin-adapted they describe correctly the singlet open-shell np excited state of 1-amino-3-propenal?

According to the Gaussian User’s Reference, with the “qcisd=s2t” keyword one can get the S2 value for this method, however, when I try to do it I obtain the following error:

QPERR --- A SYNTAX ERROR WAS DETECTED IN THE INPUT LINE.
 #QCISD=S2T
        '
 Last state="PRC1"
 TCursr= 4980 LCursr=   7
 Error termination via Lnk1e in /soft/g94/l1.exe.

Does anybody know which is the mistake I do?

Thanks in advance.

Marta --------------928F57D8CF2BA81E31873B91-- From chemistry-request@server.ccl.net Tue Dec 29 14:16:20 1998 Received: from www.ccl.net (www.ccl.net [192.148.249.5]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id OAA14425 for ; Tue, 29 Dec 1998 14:16:20 -0500 Received: from bosoleil.ci.umoncton.ca (sichelj@bosoleil.ci.umoncton.ca [139.103.2.5]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with ESMTP id OAA03234 Tue, 29 Dec 1998 14:10:39 -0500 (EST) Received: from localhost (sichelj@localhost) by bosoleil.ci.umoncton.ca (8.8.6 (PHNE_15509)/8.8.6) with SMTP id PAA03279; Tue, 29 Dec 1998 15:08:22 -0400 (AST) Date: Tue, 29 Dec 1998 15:08:22 -0400 (AST) From: "J. Sichel" X-Sender: sichelj@bosoleil.ci.umoncton.ca To: "E. Lewars" cc: chemistry@www.ccl.net Subject: Re: CCL:RATE CONSTANT AND BARRIER-QUESTION In-Reply-To: <199812282357.SAA06706@alchemy.chem.utoronto.ca> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII On Mon, 28 Dec 1998, E. Lewars wrote: > True or false: > > Two reactions with exactly the same free energies of activation (delta G > of activation, not Arrhenius activation energy) _must_ have the same > rate constants (at the same temperature). I can think of two reasons why not. 1. The transition-state-theory expression for k includes a barrier transmission coefficent (denoted by kappa) which may vary between reactions. 2. Transition-state theory may not be exact for the reactions in question. John-M. Sichel Dept. de chimie et biochimie Universite de Moncton Moncton NB, Canada