From owner-chemistry@ccl.net Tue Sep 17 01:47:00 2013 From: "Peeter Burk peeter.burk[*]ut.ee" To: CCL Subject: CCL: HOMO-LUMO of a charged molecule Message-Id: <-49178-130917014319-10814-WH7R7wORUPmkBJjRCnu+ew##server.ccl.net> X-Original-From: Peeter Burk Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1; format=flowed Date: Tue, 17 Sep 2013 08:41:03 +0300 MIME-Version: 1.0 Sent to CCL by: Peeter Burk [peeter.burk:+:ut.ee] Dear Herbert and others, Excellent clarifications in many points! I was just wondering on a few minor points: On 09/16/2013 04:47 PM, Herbert Fruchtl herbert.fruchtl%st-andrews.ac.uk wrote: > Excited state > An electron is sitting in an orbital of higher energy than the LUMO. > Keep in mind that Koopman's Theorem, which tells you that the excitation > energy is roughly the difference between HOMO and LUMO, is Wasn't the Koopmans theorem about ionisation potentials only? I can not recall the connection between Koopmans theorem and excitation energies... > a) not exact, because there is orbital relaxation after excitation, and > b) even more inexact if you rely on HF or DFT orbitals, because these > theories give rather inaccurate energies for virtual orbitals. Is there such a things as a post-HF orbitals, which can be used in Koopmans theorem like situation? My (rather limited) understanding is that if you turn to postHF (or postDFT) calculations, then your MO-s can not be any more used for Koopmans, as you have to abandon the simple picture of electron pair (or a single electron in case of SOMO) residing on one and only one MO... Perhaps somebody more knowledgeable can clarify? Best regards Peeter > > Hope this helps, > > Herbert > > On 16/09/13 06:40, salma bibi shah salmachemist88 : gmail.com wrote: >> >> Sent to CCL by: "salma bibi shah" [salmachemist88^gmail.com] >> Hi dears. >> I am a new student of computational chemistry.I experience a lot of >> problems due to lake of supervision.now a days i am working with small >> molecules for practice purpose.At the present i got the problem in >> determining HOMO-LUMO of excited molecules.When i performed open shell >> calculations with charge one i got alpha and beta both types of >> orbitals.Which orbital will be the HOMO and which one the LUMO. It >> will be either that of alpha or beta orbitals? >> Best regards> >> > From owner-chemistry@ccl.net Tue Sep 17 07:39:00 2013 From: "ankit srivastava pushpankit!A!gmail.com" To: CCL Subject: CCL: HOMO-LUMO of a charged molecule Message-Id: <-49179-130917064115-30378-Ly2wGsETIRVEQ65vxdGksw],[server.ccl.net> X-Original-From: ankit srivastava Content-Type: multipart/alternative; boundary=001a1133f3d003dad104e691f540 Date: Tue, 17 Sep 2013 16:11:02 +0530 MIME-Version: 1.0 Sent to CCL by: ankit srivastava [pushpankit : gmail.com] --001a1133f3d003dad104e691f540 Content-Type: text/plain; charset=ISO-8859-1 Dear Sir, I didn't get your point. I am too trying for HOMO-LUMO as well as for their NBO calculations but unable to understand properly. Can you explain/elaborate the answer for the question asked by Ms. Salma ? On Mon, Sep 16, 2013 at 7:17 PM, Herbert Fruchtl herbert.fruchtl% st-andrews.ac.uk wrote: > > Sent to CCL by: Herbert Fruchtl [herbert.fruchtl-x-st-andrews.**ac.uk > ] > Dear Salma, > > You are mixing a few concepts, or at least using the expressions > interchangeably. The ones you need to understand are: > > Charged molecule > This only means that the number of electrons is not balancing the nuclear > charge. In itself, has no influence on how you calculate the excitation gap. > > Open-shell molecule > You have at least one singly occupied orbital. If you do an unrestricted > calculation, you get orbital energies for alpha and beta electrons. If you > are looking for optical excitation energies, the gap you are looking for is > the one > >> from the highest occupied orbital to the lowest unoccupied of the same >> spin (but >> > see below). If there is a lower empty orbital of opposite spin, you won't > get there with a single-photon excitation (it's spin-forbidden), but there > may be other mechanisms to allow it. > > Excited state > An electron is sitting in an orbital of higher energy than the LUMO. Keep > in mind that Koopman's Theorem, which tells you that the excitation energy > is roughly the difference between HOMO and LUMO, is > a) not exact, because there is orbital relaxation after excitation, and > b) even more inexact if you rely on HF or DFT orbitals, because these > theories give rather inaccurate energies for virtual orbitals. > > Hope this helps, > > Herbert > > > On 16/09/13 06:40, salma bibi shah salmachemist88 : gmail.com wrote: > >> >> Sent to CCL by: "salma bibi shah" [salmachemist88^gmail.com] >> Hi dears. >> I am a new student of computational chemistry.I experience a lot of >> problems due to lake of supervision.now a days i am working with small >> molecules for practice purpose.At the present i got the problem in >> determining HOMO-LUMO of excited molecules.When i performed open shell >> calculations with charge one i got alpha and beta both types of >> orbitals.Which orbital will be the HOMO and which one the LUMO. It will be >> either that of alpha or beta orbitals? >> Best regards> >> >> > -- > Herbert Fruchtl > Senior Scientific Computing Officer > School of Chemistry, School of Mathematics and Statistics > University of St Andrews > -- > The University of St Andrews is a charity registered in Scotland: > No SC013532> http://www.ccl.net/cgi-bin/**ccl/send_ccl_message http://www.ccl.net/cgi-bin/**ccl/send_ccl_message chemistry/announcements/**conferences/ > > Search Messages: http://www.ccl.net/chemistry/**searchccl/index.shtml http://www.ccl.net/spammers.**txt > > RTFI: http://www.ccl.net/chemistry/**aboutccl/instructions/ > > > -- Thanks and Regards Ankit Kumar Srivastava Laser and Spectroscopy Lab Department of Physics Indian Institute of Technology Bombay, Powai, Mumbai - 400076 --001a1133f3d003dad104e691f540 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Dear Sir,
=A0 =A0 =A0 I didn't get your point. I a= m too trying for HOMO-LUMO as well as for their NBO calculations but unable= to understand properly.=A0
Can you explain/elaborate the answer = for the question asked by Ms. Salma ?


On Mon,= Sep 16, 2013 at 7:17 PM, Herbert Fruchtl herbert.fruchtl%st-andrews.ac.uk <owner-chemistry[*]ccl.net= > wrote:

Sent to CCL by: Herbert Fruchtl [herbert.fruchtl-x-st-andrews.ac.uk= ]
Dear Salma,

You are mixing a few concepts, or at least using the expressions interchang= eably. The ones you need to understand are:

Charged molecule
This only means that the number of electrons is not balancing the nuclear c= harge. In itself, has no influence on how you calculate the excitation gap.=

Open-shell molecule
You have at least one singly occupied orbital. If you do an unrestricted ca= lculation, you get orbital energies for alpha and beta electrons. If you ar= e looking for optical excitation energies, the gap you are looking for is t= he one
> from the highest occupied orbital to the lowest unoccupied of the same spin= (but
see below). If there is a lower empty orbital of opposite spin, you won'= ;t get there with a single-photon excitation (it's spin-forbidden), but= there may be other mechanisms to allow it.

Excited state
An electron is sitting in an orbital of higher energy than the LUMO. Keep i= n mind that Koopman's Theorem, which tells you that the excitation ener= gy is roughly the difference between HOMO and LUMO, is
a) not exact, because there is orbital relaxation after excitation, and
b) even more inexact if you rely on HF or DFT orbitals, because these theor= ies give rather inaccurate energies for virtual orbitals.

Hope this helps,

=A0 Herbert


On 16/09/13 06:40, salma bibi shah salmachemist88 : gmail.com wrote:

Sent to CCL by: "salma =A0bibi shah" [salmachemist88^gmail.com]
Hi dears.
I am a new student of computational chemistry.I experience a lot of problem= s due to lake of supervision.now a days i am working with small molecules f= or practice purpose.At the present i got the problem in determining HOMO-LU= MO of excited molecules.When i performed open shell calculations with charg= e one i got alpha and beta both types of orbitals.Which orbital will =A0be = the HOMO and which one the LUMO. It will be either that of alpha or beta or= bitals?
Best regards>


--
Herbert Fruchtl
Senior Scientific Computing Officer
School of Chemistry, School of Mathematics and Statistics
University of St Andrews
--
The University of St Andrews is a charity registered in Scotland:
No SC013532




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--
= Thanks and Regards
Ankit Kumar Srivastava
Laser and Spectroscopy Lab
D= epartment of Physics
Indian Institute of Technology Bombay,
Powai,=A0= Mumbai - 400076
--001a1133f3d003dad104e691f540-- From owner-chemistry@ccl.net Tue Sep 17 14:17:00 2013 From: "Mikael Johansson mikael.johansson/./iki.fi" To: CCL Subject: CCL: HOMO-LUMO of a charged molecule Message-Id: <-49180-130917141422-16086-SeJ9tFt3NUkDlIwi70iy1Q{}server.ccl.net> X-Original-From: Mikael Johansson Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Date: Tue, 17 Sep 2013 21:14:09 +0300 (EEST) MIME-Version: 1.0 Sent to CCL by: Mikael Johansson [mikael.johansson * iki.fi] Hello Peeter and All, On Tue, 17 Sep 2013, Peeter Burk peeter.burk[*]ut.ee wrote: > Wasn't the Koopmans theorem about ionisation potentials only? I can not > recall the connection between Koopmans theorem and excitation energies... The original from 1934, yes. For a good read on extension to DFT and excitation energies, see Gritsenko & Baerends, "The analog of Koopmans' theorem for virtual Kohn-Sham orbital energies": http://dx.doi.org/10.1139/V09-088 > Is there such a things as a post-HF orbitals, which can be used in Koopmans > theorem like situation? My (rather limited) understanding is that if you turn > to postHF (or postDFT) calculations, then your MO-s can not be any more used > for Koopmans, as you have to abandon the simple picture of electron pair (or > a single electron in case of SOMO) residing on one and only one MO... Perhaps > somebody more knowledgeable can clarify? That's when the Extended Koopmans' Theorem comes in, formulated twice in the mid-70's: 1.) Day, Smith & Garrod, "A generalization of the Hartree-Fock one-particle potential", http://dx.doi.org/10.1002/qua.560080855 2.) Morrell, Parr & Levy, "Calculation of ionization potentials from density matrices and natural functions, and the long-range behavior of natural orbitals and electron density", http://dx.doi.org/10.1063/1.430509 For a recent discussion on the EKT, see Ernzerhof, "Validity of the Extended Koopmans' Theorem", http://dx.doi.org/10.1021/ct800552k Cheers, Mikael J. http://www.iki.fi/~mpjohans/ From owner-chemistry@ccl.net Tue Sep 17 17:38:00 2013 From: "Basma Ghazal basmaghazal * ymail.com" To: CCL Subject: CCL: Problem in visualization of HOMO and LUMO orbitals using Gview Message-Id: <-49181-130917170204-13423-7+eGSb5nZGMLSTxgrPCiXA-$-server.ccl.net> X-Original-From: Basma Ghazal Content-Type: multipart/alternative; boundary="-1572413313-1745536164-1379451713=:19850" Date: Tue, 17 Sep 2013 14:01:53 -0700 (PDT) MIME-Version: 1.0 Sent to CCL by: Basma Ghazal [basmaghazal#%#ymail.com] ---1572413313-1745536164-1379451713=:19850 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Hello,=0A=A0I do optimization for metal complexes of halogenated phthalocya= nine by using (#b3lyb/6-31G (d) opt) method but I couldn't calculate freque= ncy till now due to my computer facilities [core i7-3840 QM cpu 2.8 GHz ,RA= M (32), 64 operating system].=0A=A0=0ANow, I tried to visualize HOMO and LU= MO for the optimized metal complexes using (.fchk) file, but I have an erro= r termination in cubegen formation:=0AError termination via Lnk1e at Mon Se= p 16 16:29:47 2013.=0ACubegen Job Completed (PID =3D 1b38, status =3D 2057)= =0ACubegen Series Job Completed =0A=A0=0ACould you kindly tell me how to in= crease the grid file?=0A=A0And please could you suggest any tutorial or boo= k to learn more about this kinds of calculations.=0A=A0Best Regards,=0ABasm= a=0A=A0=0A=A0=0A=0A----------------------------------- =0ABasma S. Ghazal= =0AMSc. Organic Chemistry =0ATherapeutical Chemistry Department =0ANational= Research Center, Egypt.=0A =0AE-mail : basmaghazal.:.ymail.com =0A=A0=A0=A0= =A0=A0=A0=A0=A0=A0basmaghazal.:.gmail.com ---1572413313-1745536164-1379451713=:19850 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
=0A=0A
Hello,
 I do optimization for metal complex= es of halogenated phthalocyanine by using (#b3lyb/6-31G (d) opt) method but= I couldn't calculate frequency till now due to my computer facilities [cor= e i7-3840 QM cpu 2.8 GHz ,RAM (32), 64 operating system].
 
<= div class=3D"MsoNormal" style=3D"margin: 0in 0in 8pt;">Now, I tried to v= isualize HOMO and LUMO for the optimized metal complexes using (.fchk) file, but I have an error termination in cub= egen formation:

Error termination via Lnk1e at Mon = Sep 16 16:29:47 2013.
Cubegen Job Completed (PID =3D 1b38, status =3D 20= 57)
Cubegen Series Job Completed
 
Coul= d you kindly tell me how to increase the grid file?
 And please cou= ld you suggest any tutorial or book to learn more about this kinds of calcu= lations.
 Best Regards,
Basma
 
 
=0A=0A
 =
-----------------------------------
=0A
<= font color=3D"#0000bf" style=3D"background-color: rgb(255, 255, 255);">Basm= a S. Ghazal
<= span style=3D"color: rgb(0, 0, 0);">MSc. Organic Chemistry
=0A
= Therapeutical Chemistry Department
National Research Center, Egypt.
=0A
E-mai= l : basmaghazal.:.ymail.com
=0A
   &= nbsp;     basmaghazal.:.gmail.= com

---1572413313-1745536164-1379451713=:19850--