From owner-chemistry@ccl.net Tue Aug 8 14:07:00 2006 From: "Walkimar Carneiro walk---vm.uff.br" To: CCL Subject: CCL: Weight of Lewis structure Message-Id: <-32354-060808134911-8059-zk8cNh+6A65xl8Gf1um3Sw^_^server.ccl.net> X-Original-From: "Walkimar Carneiro" Date: Tue, 8 Aug 2006 13:49:09 -0400 Sent to CCL by: "Walkimar Carneiro" [walk+*+vm.uff.br] In cases were it is possible to write several different Lewis structure to the same molecule, does anybody know how to quantify the weight of each Lewis structure to the final hybrid? Sincerely Walkimar From owner-chemistry@ccl.net Tue Aug 8 15:29:00 2006 From: "Sergio Emanuel Galembeck segalemb ~ usp.br" To: CCL Subject: CCL: Weight of Lewis structure Message-Id: <-32355-060808144137-27403-1R4IqcLSQ7t8nU1vHTpwLA||server.ccl.net> X-Original-From: Sergio Emanuel Galembeck Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=ISO-8859-1 Date: Tue, 08 Aug 2006 15:41:26 -0300 MIME-Version: 1.0 Sent to CCL by: Sergio Emanuel Galembeck [segalemb-$-usp.br] Dear Walkimar, There are few ways to quantify the contributions of Lewis structures: - Natural Resonance Theory, from Frank Weinhold. It works well. - Valence Bond, in VB2000 software. I am begining to use this software. - For aromatic compounds, HOSE, from T. M. Krygowski, a very simple method. If you need more information, please contact me, Best regards, Sergio Galembeck Citando "Walkimar Carneiro walk---vm.uff.br" : > Sent to CCL by: "Walkimar Carneiro" [walk+*+vm.uff.br] > In cases were it is possible to write several different Lewis structure to > the same molecule, does anybody know how to quantify the weight of each Lewis > structure to the final hybrid? > > Sincerely > Walkimar> > > > From owner-chemistry@ccl.net Tue Aug 8 16:35:00 2006 From: "zborowsk^-^chemia.uj.edu.pl" To: CCL Subject: CCL: Weight of Lewis structure Message-Id: <-32356-060808163330-31485-/PlaBlUin3EZ+wI+CkVcFw|a|server.ccl.net> X-Original-From: zborowsk(0)chemia.uj.edu.pl Content-Transfer-Encoding: 8bit Content-Type: text/plain;charset=iso-8859-2 Date: Tue, 8 Aug 2006 22:33:23 +0200 (CEST) MIME-Version: 1.0 Sent to CCL by: zborowsk{}chemia.uj.edu.pl Hi You can do that using a HOSE model. You need only the equilibrium geometry for your system (bond lenghts exactly). But HOSE is an empirical model and not all bonds are parametrized, so here can be a problem. I can tell you if the HOSE model can be useful for you but let me know more details about your system. (It is a bit more complicated job, but it is possible to calculate the missing parameters) regards Kzys > Sent to CCL by: "Walkimar Carneiro" [walk+*+vm.uff.br] > In cases were it is possible to write several different Lewis structure to > the same molecule, does anybody know how to quantify the weight of each > Lewis structure to the final hybrid? > > Sincerely > Walkimar> > > > -- Krzysztof Zborowski Faculty of Chemistry Jagiellonian University 3 Ingardena Street 30-060 Krakow Poland phone: +48(12)632-4888 ext. 2064 or 2067 fax: +48(12)634-05-15 email: zborowsk:+:chemia.uj.edu.pl ICQ 158385743 gg 3817259 skype kzys70 From owner-chemistry@ccl.net Tue Aug 8 18:25:00 2006 From: "Herbert Fruchtl herbert.fruchtl*_*st-andrews.ac.uk" To: CCL Subject: CCL:G: MP2 HOMO-LUMO gap with G03 Message-Id: <-32357-060808125302-3665-0nYNsKKITqbIeMhN4jwGhQ^^server.ccl.net> X-Original-From: "Herbert Fruchtl" Date: Tue, 8 Aug 2006 12:53:02 -0400 Sent to CCL by: "Herbert Fruchtl" [herbert.fruchtl!^!st-andrews.ac.uk] Something I should probably know, but... I am calculating the HOMO-LUMO gap of small organic molecules with HF, DFT and MP2 using Gaussian 03. For MP2, I use the keywords "Density=MP2 Pop=Regular", and the output says that the MP2 density is used. The numbers for HF and MP2 are extremely close (at least 3 digits). Is this to be expected, or is there something I am missing? I assume a better way to get vertical excitation energies would be to calculate the first roots with CIS or TDDFT. Is this correct? Herbert From owner-chemistry@ccl.net Tue Aug 8 22:05:00 2006 From: "Karthikeyan Swaminathan swamink]^[email.uc.edu" To: CCL Subject: CCL: Polygamma functions Message-Id: <-32358-060808203235-24300-sSf71vWAguoQUUQXXAHEzw^-^server.ccl.net> X-Original-From: "Karthikeyan Swaminathan" Date: Tue, 8 Aug 2006 20:32:35 -0400 Sent to CCL by: "Karthikeyan Swaminathan" [swamink(-)email.uc.edu] Hi, I am trying to implement (code) the statistical functions of Digamma, Trigamma and Tetragamma for a software package. If any of you know good literature on this topic, could you please point me to it? Thanks and regards Karthik Grad Student Univ of Cincinnati From owner-chemistry@ccl.net Tue Aug 8 22:40:01 2006 From: "Joaquin Barroso Flores joaco_barroso###yahoo.com" To: CCL Subject: CCL: Weight of Lewis structure Message-Id: <-32359-060808223445-20862-CYuXm2lI+pPtMhBydKEtYg _ server.ccl.net> X-Original-From: Joaquin Barroso Flores Content-Transfer-Encoding: 8bit Content-Type: multipart/alternative; boundary="0-1865870463-1155090877=:60590" Date: Tue, 8 Aug 2006 21:34:37 -0500 (CDT) MIME-Version: 1.0 Sent to CCL by: Joaquin Barroso Flores [joaco_barroso|a|yahoo.com] --0-1865870463-1155090877=:60590 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit The easiest way to assess this is by the use of Natural Resonance Theory (NRT), available in the NBO 5.0 package. I think all you need is to define the molecule and the program starts searching for different possible lewis structures and then weights them within the optimized wavefunction. I'm not really sure how different would be this than doing General Valence Bond, and weighting them by yourself but then again the NBO basis set seems more fitted to do this job since you are using a localized set of orbitals to describe a localized set of bonds. Hope this helps Greetings Joaquin Barroso-Flores "Walkimar Carneiro walk---vm.uff.br" escribió: Sent to CCL by: "Walkimar Carneiro" [walk+*+vm.uff.br] In cases were it is possible to write several different Lewis structure to the same molecule, does anybody know how to quantify the weight of each Lewis structure to the final hybrid? Sincerely Walkimarhttp://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp://www.ccl.net/chemistry/sub_unsub.shtmlhttp://www.ccl.net/spammers.txt__________________________________________________ Correo Yahoo! 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The easiest way to assess this is by the use of Natural Resonance Theory (NRT), available in the NBO 5.0 package. I think all you need is to define the molecule and the program starts searching for different possible lewis structures and then weights them within the optimized wavefunction. I'm not really sure how different would be this than doing General Valence Bond, and weighting them by yourself but then again the NBO basis set seems more fitted to do this job since you are using a localized set of orbitals to describe a localized set of bonds.
 
Hope this helps
Greetings
 
Joaquin Barroso-Flores

"Walkimar Carneiro walk---vm.uff.br" <owner-chemistry---ccl.net> escribió:
Sent to CCL by: "Walkimar Carneiro" [walk+*+vm.uff.br]
In cases were it is possible to write several different Lewis structure to the same molecule, does anybody know how to quantify the weight of each Lewis structure to the final hybrid?

Sincerely
Walkimar


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