From owner-chemistry@ccl.net Thu Apr 14 12:32:01 2011 From: "P.D.Jarowski.\a/.surrey.ac.uk" To: CCL Subject: CCL: Diffuse functions Message-Id: <-44376-110414123007-13116-I0wan5JuQk9EydnR84yNPA\a/server.ccl.net> X-Original-From: Content-Language: en Content-Type: multipart/alternative; boundary="_000_C9CCDF8E1551pj0013surreyacuk_" Date: Thu, 14 Apr 2011 17:29:52 +0100 MIME-Version: 1.0 Sent to CCL by: [P.D.Jarowski]^[surrey.ac.uk] --_000_C9CCDF8E1551pj0013surreyacuk_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi, thanks. Yes I tried that and the orbitals on the donor side got a littl= e bigger. I guess I was looking for a general conclusion about diffuse func= tions. In my experience, the general conclusions and shape of orbitals is r= ather basis set independent and I was hoping for someone to confirm that fo= r me. Do you know if this is indeed true? Hard to find such things in the literature. If anyone has a reference that = would be great. Best Regards, Peter On 4/14/11 3:31 PM, "Abrash, Sam sabrash(0)richmond.edu" wrote: What method did you use to determine the LUMO? If you only used a ground s= tate method to describe the virtual orbitals (the lowest energy of which is= the LUMO), then the LUMO description is almost certainly incorrect. Try u= sing TDDFT rather than a ground state method. In addition to determine whether the difference in your results is due to t= he finite field method or the basis set, rerun your DFT results using the d= iffuse basis set and compare the results. Good luck! Sam Samuel A. Abrash Department of Chemistry University of Richmond Richmond, VA 23173 Phone: 804-289-8248 Fax: 804-287-1897 E-mail: sabrash^-^richmond.edu Web-page: http://www.richmond.edu/~sabrash "In 1893 Charles Hinton left Japan to become a mathematics instructor at Pr= inceton University, where he invented a baseball-pitching machine that used= gunpowder to propel the balls, like a cannon. After several accidents, th= e device was abandoned and Hinton lost his job ..." Terry Pratchett, Ian St= eward and Jack Cohen, The Science of Diskworld III > From: owner-chemistry+sabrash=3D=3Drichmond.edu^-^ccl.net [mailto:owner-chemi= stry+sabrash=3D=3Drichmond.edu^-^ccl.net] On Behalf Of P.D.Jarowski{:}surrey.= ac.uk Sent: Thursday, April 14, 2011 4:53 AM To: Abrash, Sam Subject: CCL: Diffuse functions Dear all, I am facing a problem in the molecular orbital representation of some dipol= ar chromophores using two different methods. In the first case we have a b3= lyp /6-31g(d) homo and lumo level where there is almost equal density on bo= th the donor and acceptor portion of the molecule. In other words, the eige= nstates are very delocalized. When using a finite field method with a 6-31+= +g basis the homo has most of the density on the donor and in the lumo its = mostly on the acceptor, the eigenstates are more localized. Here is my question: could the implementation of the diffuse functions caus= e this difference? Would a finite field method lead to greater localization of these eigenstat= es? The interpretation of our experimental data will depend heavily on the over= lap of the eigenstates. Thanks in advance. ***Sent via RoadSync=AE for Android(tm) --_000_C9CCDF8E1551pj0013surreyacuk_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Re: CCL: Diffuse functions Hi, thanks. Yes I tried that and the orbitals on the donor side got a= little bigger. I guess I was looking for a general conclusion about diffus= e functions. In my experience, the general conclusions and shape of orbital= s is rather basis set independent and I was hoping for someone to confirm t= hat for me. Do you know if this is indeed true?

Hard to find such things in the literature. If anyone has a reference that = would be great.

Best Regards,

Peter


On 4/14/11 3:31 PM, "Abrash, Sam sabrash(0)richmond.edu" <owner-chemistry^-^ccl.net> wrote:

What method did you use to determine t= he LUMO?=A0 If you only used a ground state method to describe the virtual = orbitals (the lowest energy of which is the LUMO), then the LUMO descriptio= n is almost certainly incorrect.=A0 Try using TDDFT rather than a ground st= ate method.
 
In addition to determine whether the difference in your results is due to t= he finite field method or the basis set, rerun your DFT results using the d= iffuse basis set and compare the results.
 
Good luck!
 
Sam
 
Samuel A. Abrash
Department of Chemistry
University of Richmond
Richmond, VA 23173
Phone:=A0 804-289-8248
Fax:=A0 804-287-1897
E-mail:=A0 sabrash^-^richmond.edu <mailto:sabrash^-^richmond.edu> <= BR> Web-page:=A0 http://www.richmo= nd.edu/~sabrash <h= ttp://oncampus.richmond.edu/~sabrash>
"In 1893 Charles Hinton left Japan to become a mat= hematics instructor at Princeton University, where he invented a baseball-p= itching machine that used gunpowder to propel the balls, like a cannon. &nb= sp;After several accidents, the device was abandoned and Hinton lost his jo= b ..." Terry Pratchett, Ian Steward and Jack Cohen, The Science of Dis= kworld III

From: owner-chemistry+sabrash=3D=3Drichmond.e= du^-^ccl.net [mailto:owner-chemistry+sabrash=3D=3Drichmond.edu^-^ccl.net] = On Behalf Of P.D.Jarowski{:}surrey.ac.uk
Sent: Thursday, April 14, 2011 4:53 AM
To: Abrash, Sam
Subject: CCL: Diffuse functions
Dear all,

I am facing a problem in the molecular orbital representation of some dipol= ar chromophores using two different methods. In the first case we have a b3= lyp /6-31g(d) homo and lumo level where there is almost equal density on bo= th the donor and acceptor portion of the molecule. In other words, the eige= nstates are very delocalized. When using a finite field method with a 6-31+= +g basis the homo has most of the density on the donor and in the lumo its = mostly on the acceptor, the eigenstates are more localized.

Here is my question: could the implementation of the diffuse functions caus= e this difference?

Would a finite field method lead to greater localization of these eigenstat= es?

The interpretation of our experimental data will depend heavily on the over= lap of the eigenstates.

Thanks in advance.

***Sent via RoadSync® for Android™

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