From owner-chemistry@ccl.net Mon May 25 08:43:00 2009 From: "Mahmoud A. A. Ibrahim m.ibrahim1982],[yahoo.com" To: CCL Subject: CCL:G: Experimental and theratical UV calculation Message-Id: <-39369-090525083030-27481-RXas2LdUfOhuJ7NBQRbQog%server.ccl.net> X-Original-From: "Mahmoud A. A. Ibrahim" Content-Type: multipart/alternative; boundary="0-1721251397-1243251014=:82131" Date: Mon, 25 May 2009 04:30:14 -0700 (PDT) MIME-Version: 1.0 Sent to CCL by: "Mahmoud A. A. Ibrahim" [m.ibrahim1982|a|yahoo.com] --0-1721251397-1243251014=:82131 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Dear Saurabh=20 Sure we can, we can compare theoretical calculations with the experimental = one. But you should be aware of some points, firstly, your structure should be t= he optimized one (I don't mean here after optimization, I mean your structu= re is the structure of the experimental one under solvation effect). About, the number of states, it is depending on you experimental one, for e= xample your experimental lamda max is around 280nm (for example) and your r= un your TD calculation based on 10 states and found the your excitation sta= tes didn't reached the desired one (i.e. 280nm) and stops at 300nm, so you = should Add more states. So, there is no optimum number of states. You start= with small number and then add more states until reach your desired wavele= ngth. Sure, solvation has a big big effect on your TD calculations and on all cal= culations in general. And here I would like to send a small experience in s= tudying solvation effect, DON'T Trust always in solvation modeling, Some ti= mes you have to add explicit water molecules. Through out the last of weeks I was doing theoretical UV Data for some comp= lexes, so if you like me to have a look on your UV spectra (theoretical and= expremental one), send it. But, there is one keyword I couldn't understand its effect, it is called Eq= Solv. It says makes equilibrium solvation on your system using PCM model. B= ut, it doesn't add solvation model and you need to add solvation model keyw= ord in addition to Eqsolv. I would like to push you forward and say you can get the same exactly UV sp= ectra theoretical as the experimental one, but the problem is to mimic your= system well. Sincerely; M. Ibrahim Mahmoud A. A. Ibrahim Current Address School of Chemistry, University of Manchester,=20 Oxford Road, Manchester, M13 9PL, United Kingdom. Mahmoud.Ibrahim-2:-:postgrad.manchester.ac.uk=20 =20 Home Address =20 Chemistry Department, Faculty of Science,=20 Minia University,=20 Minia 61519,Egypt.=20 M.Ibrahim1982:-:yahoo.com=20 Mobile Phone No.: +20102554083 =20 Land Phone No.: +20226635916=20 Fax No.: +20862342601 --- On Mon, 5/25/09, Ismael Ortiz Verano ieortizv*bt.unal.edu.co wrote: > From: Ismael Ortiz Verano ieortizv*bt.unal.edu.co Subject: CCL:G: Experimental and theratical UV calculation To: "Ibrahim, Mahmoud A. A. " Date: Monday, May 25, 2009, 11:35 AM Saurabh Perhaps 15 states are not sufficient, and in order to get accord with the e= xperiment, you can calculate more states (try 40 or 50). I think that when you compare your theoretical results, you obtain only wav= elenghts of low energy (red).=20 =0A=0A If you are looking for a better accord, you can carry out a calculation tha= t includes solvent's effect. --=20 Ismael Ortiz Grupo de Qu=EDmica Te=F3rica Universidad Nacional de Colombia Tel: (57)(1) 3165000 ext 10608 =0A=0A 2009/5/23 Saurabh Agrawal Saurabh.Agrawal!A!ucdconnect.ie =0A=0AHello, I have calculated UV=A0absorption spectrum for some molecules using Gaussia= n. With the following basis set and cards. =0A=0A #p B3LYP/6-31g** TD(Singlet,NSTATES=3D15) guess=3Dread geom=3Dcheck The results I got are considerably different from experimental results.=20 1) Can we compare the theoretical results with experimental results? I appr= eciate if some one could send link for some basic notes on it. =0A=0A Sincere regards, Saurabh Saurabh=A0Agrawal, PhD Student, Department of Chemical and Bioprocess=A0Engineering, UCD, Belfield, Dublin-4, Ireland =0A --=20 Ismael Ortiz Verano Grupo de Qu=EDmica Te=F3rica Universidad Nacional de Colombia Tel: (57)(1) 3165000 ext 10608 =0A=0A=0A=0A --0-1721251397-1243251014=:82131 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
=0A=0A=0A=0A --0-1721251397-1243251014=:82131--
Dear Saurabh
Sure we can, we can compare = theoretical calculations with the experimental one.
But you should be aw= are of some points, firstly, your structure should be the optimized one (I = don't mean here after optimization, I mean your structure is the structure = of the experimental one under solvation effect).
About, the= number of states, it is depending on you experimental one, for example you= r experimental lamda max is around 280nm (for example) and your run your TD= calculation based on 10 states and found the your excitation states didn't= reached the desired one (i.e. 280nm) and stops at 300nm, so you should Add= more states. So, there is no optimum number of states. You start with smal= l number and then add more states until reach your desired wavelength.
S= ure, solvation has a big big effect on your TD calculations and on all calculations in general. And here I would like to send a small experience = in studying solvation effect, DON'T Trust always in solvation modeling, Som= e times you have to add explicit water molecules.
Through out the last o= f weeks I was doing theoretical UV Data for some complexes, so if you like = me to have a look on your UV spectra (theoretical and expremental one), sen= d it.
But, there is one keyword I couldn't understand its effect, it is = called EqSolv. It says makes equilibrium solvation on your system using PCM= model. But, it doesn't add solvation model and you need to add solvation m= odel keyword in addition to Eqsolv.
I would like to push you forward and= say you can get the same exactly UV spectra theoretical as the experimenta= l one, but the problem is to mimic your system well.
Sincerely;
M. Ib= rahim

Mahmoud A. A. Ibrahim

Current Address
School of Chemistry, Univers= ity of Manchester,
Oxford Road, Manchester, M13 9PL, United Kingdom.Mahmoud.Ibrahim-2:-:postgrad.manchester.ac.uk

Home = Address
Chemistry Department, Faculty of S= cience,
Minia University,
M= inia 61519,Egypt.
M.Ibrahim1982:-:yahoo.com
Mobile Pho= ne No.: +20102554083
L= and Phone No.: +20226635916
Fax No.: +20862342601


--- On Mon, 5/25/09, Ismael Ortiz Verano ieortizv*bt.unal.edu.c= o <owner-chemistry:-:ccl.net> wrote:

From: Ismael Ortiz Verano ieortizv*bt.unal.edu.co <owner-chemist= ry:-:ccl.net>
Subject: CCL:G: Experimental and theratical UV calculatio= n
To: "Ibrahim, Mahmoud A. A. " <m.ibrahim1982:-:yahoo.com><= br>Date: Monday, May 25, 2009, 11:35 AM

Saur= abh

Perhaps 15 states are not sufficient, and in order to get accord= with the experiment, you can calculate more states (try 40 or 50).

= I think that when you compare your theoretical results, you obtain only wav= elenghts of low energy (red).
=0A=0A
If you are looking for a better= accord, you can carry out a calculation that includes solvent's effect.
--
Ismael Ortiz
Grupo de Qu=EDmica Te=F3rica
Universidad Nac= ional de Colombia
Tel: (57)(1) 3165000 ext 10608
=0A=0A

2009/5/23 Saurabh Agrawal Saurabh.Agrawal!A!ucdconnect.ie= <owner-chemistry*o*ccl.net>
=0A=0A
Hello,

I have calculated UV=  absorption spectrum for some molecules using Gaussian. With the follo= wing basis set and cards.
=0A=0A
#p B3LYP/6-31g** TD(Singlet,NSTATES= =3D15) guess=3Dread geom=3Dcheck

The results I got are considerably = different from experimental results.

1) Can we compare the theoreti= cal results with experimental results? I appreciate if some one could send = link for some basic notes on it.
=0A=0A
Sincere regards,

Saura= bh



Saurabh Agrawal,
PhD Student,
Department of Ch= emical and Bioprocess Engineering,
UCD, Belfield,
Dublin-4, Irel= and
=0A



--
Ismael Ortiz = Verano
Grupo de Qu=EDmica Te=F3rica
Universidad Nacional de Colombia<= br>Tel: (57)(1) 3165000 ext 10608
=0A