CCL:G: Gaussian IR frequency calculation



Dear André,

Thanks for your adviceI

Regards
Gustavo Gotelli

Polymer Development

 

De: owner-chemistry+ggotelli==kaliumtech.com(~)ccl.net [mailto:owner-chemistry+ggotelli==kaliumtech.com(~)ccl.net] En nombre de André Farias de Moura moura_-_ufscar.br
Enviado el: sábado, 21 de marzo de 2015 15:38
Para: Gotelli, Gustavo A
Asunto: CCL:G: Gaussian IR frequency calculation

 

not really a Gaussian issue, the frequencies from the standard harmonic oscillator model need to be scaled. Scaling factor depend on your choice of basis set and level of theory, so you need to find out if anybody has ever published a scaling factor for your specific choices (rb3lyp/6-311++g(d,p)), otherwise you have to obtain the proper factor by yourself. for the unrestricted case, take a look at: J. Phys. Chem. A2005109 (12), pp 2937–2941, for instance.

 

best

 

André

 

On Sat, Mar 21, 2015 at 12:46 PM, Gustavo A Gotelli ggotelli*|*kaliumtech.com <owner-chemistry|,|ccl.net> wrote:


Sent to CCL by: "Gustavo A Gotelli" [ggotelli- -kaliumtech.com]
Hi all!

I'm using G03W for doing an IR frequency calculation using the 6-311g basis
set,
# opt freq rb3lyp/6-311++g(d,p) pop=savemixed geom=connectivity scf=tight

The problem is that results are far from experimental data, with
differences around 300/400 cm-1 between calculated and experimental peaks.
I guess is because I'm using wrong parameters, perhaps the basis set.
Can somebody suggest how to get results that better fits experimental data?

Thanks in advance
Gustavo



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--

_____________

Prof. Dr. André Farias de Moura
Department of Chemistry
Federal University of São Carlos
São Carlos - Brazil
phone: +55-16-3351-8090