From owner-chemistry@ccl.net Tue Apr 23 14:30:00 2019 From: "Jeya Vimalan jeyavimalan2k]_[gmail.com" To: CCL Subject: CCL: IR intensity : DFT Vs Experiments Message-Id: <-53700-190423142926-5401-kSW/mcs4eAw9CtI1FP0kvw()server.ccl.net> X-Original-From: Jeya Vimalan Content-Type: multipart/alternative; boundary="0000000000007bb973058736c35b" Date: Tue, 23 Apr 2019 11:29:10 -0700 MIME-Version: 1.0 Sent to CCL by: Jeya Vimalan [jeyavimalan2k===gmail.com] --0000000000007bb973058736c35b Content-Type: text/plain; charset="UTF-8" Dear All, I have a basic question regarding the Intensities listed by DFT in particular in G09. I am trying to compare it with experiments, but they are usually two different units. Can anyone help me with the simplest way, by which the DFT intensities can be compared to the experimental means. Any scripts or pointers will be really helpful. Thanks. Vimal. --0000000000007bb973058736c35b Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Dear All,

I have a basic question regar= ding the Intensities listed by DFT in particular in G09.
I am try= ing to compare it with experiments, but they are usually two different unit= s.

Can anyone help me with the simplest way, by wh= ich the DFT intensities can be compared to the experimental means.

Any scripts or pointers will be really helpful.=C2=A0

Thanks.
Vimal.
=C2=A0
--0000000000007bb973058736c35b-- From owner-chemistry@ccl.net Tue Apr 23 16:34:00 2019 From: "Steve Williams willsd^-^appstate.edu" To: CCL Subject: CCL: IR intensity : DFT Vs Experiments Message-Id: <-53701-190423163258-18697-XHjIhWLT914tLfTT4EBbNQ#%#server.ccl.net> X-Original-From: Steve Williams Content-Type: multipart/alternative; boundary="00000000000048d91e0587387dae" Date: Tue, 23 Apr 2019 16:32:41 -0400 MIME-Version: 1.0 Sent to CCL by: Steve Williams [willsd,appstate.edu] --00000000000048d91e0587387dae Content-Type: text/plain; charset="UTF-8" You will need to have absolute IR intensity, and you need to know if IR absorbances are measured using base-10 logs or natural (Naperian) logs. If you have all of these under control even quite modest basis sets and quite old functionals can give predicted IR intensity that is within 10% to 20% of experimentally measured IR band areas. To see how well this can work for alkanes using B3LYP with the relatively small 6-31+G(d,p) basis set, see J. Quan. Spec. Rad. Trans. Volume 129, pages 298-307, 2013. The appendix also has a justification for a conversion factor from km/mol to a few commonly used absolute IR intensity units. Steve On Tue, Apr 23, 2019, 4:04 PM Jeya Vimalan jeyavimalan2k]_[gmail.com < owner-chemistry*|*ccl.net> wrote: > Dear All, > > I have a basic question regarding the Intensities listed by DFT in > particular in G09. > I am trying to compare it with experiments, but they are usually two > different units. > > Can anyone help me with the simplest way, by which the DFT intensities can > be compared to the experimental means. > > Any scripts or pointers will be really helpful. > > Thanks. > Vimal. > > > --00000000000048d91e0587387dae Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
You will need to have absolute IR=C2=A0 intensity, and yo= u need to know if IR absorbances are measured using base-10 logs or natural= (Naperian) logs.

If you have = all of these under control even quite modest basis sets and quite old funct= ionals can give predicted IR intensity that is within 10% to 20% of experim= entally measured IR band areas.

To see how well this can work for alkanes using B3LYP=C2=A0 with = the relatively small 6-31+G(d,p) basis set, see J. Quan. Spec. Rad. Trans. = Volume 129, pages 298-307, 2013. The appendix also has a justification for = a conversion factor from km/mol to a few commonly used absolute IR intensit= y units.

Steve

On T= ue, Apr 23, 2019, 4:04 PM Jeya Vimalan jeyavimalan2k]_[gmail.com <owner= -chemistry*|*ccl.net> wrote:
<= div dir=3D"ltr">Dear All,

I have a basic question regard= ing the Intensities listed by DFT in particular in G09.
I am tryi= ng to compare it with experiments, but they are usually two different units= .

Can anyone help me with the simplest way, by whi= ch the DFT intensities can be compared to the experimental means.

Any scripts or pointers will be really helpful.=C2=A0
=

Thanks.
Vimal.
=C2=A0
--00000000000048d91e0587387dae--