From owner-chemistry@ccl.net Sat Jan 12 13:35:00 2019 From: "Jens Spanget-Larsen spanget^^ruc.dk" To: CCL Subject: CCL: SV: Looking for a PPP parameter set Message-Id: <-53584-190112044243-25507-n3XEpbwwIeYrzH2bUbQ4wQ a server.ccl.net> X-Original-From: Jens Spanget-Larsen Content-Language: da-DK Content-Type: multipart/alternative; boundary="_000_A94E15A372E6194CA8719D62642F674401374B5E80MBX2adrucdk_" Date: Sat, 12 Jan 2019 09:42:35 +0000 MIME-Version: 1.0 Sent to CCL by: Jens Spanget-Larsen [spanget+/-ruc.dk] --_000_A94E15A372E6194CA8719D62642F674401374B5E80MBX2adrucdk_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Dear Gustavo! Whether you use MN or OH two-center electron repulsion integrals does not d= epend so much on the other PPP parameters. The choice depends primarily on = the configuration interaction (CI) expansion. If the expansion is limited t= o singly excited configurations (CIS), the strongly screened MN integrals t= end to be adequate. But if you include doubly or higher excited configurati= ons, thereby explicitly introducing terms in electron correlation, the less= screened OH integrals are more appropriate. You want to include distance depending resonance integrals (beta's). Let me= just mention that if you include resonance integrals between 'non-bonded' = centers, thereby abandoning the tight-binding approximation, you break the = spirit of the PPP concept. Yours, Jens >--< ------------------------------------------------------ JENS SPANGET-LARSEN Office: +45 4674 2710 Dept. of Science Fax: +45 4674 3011 Roskilde University Mobile: +45 2320 6246 P.O.Box 260 Mail: spanget\a/ruc.dk DK-4000 Roskilde, Denmark Web: thiele.ruc.dk/~spanget ------------------------------------------------------ ________________________________________ Fra: owner-chemistry+spanget=3D=3Druc.dk\a/ccl.net [owner-chemistry+spanget= =3D=3Druc.dk\a/ccl.net] på vegne af Gustavo L.C. Moura gustavo.moura(0)u= fpe.br [owner-chemistry\a/ccl.net] Sendt: 12. januar 2019 01:19 Til: Jens Spanget-Larsen Emne: CCL: Looking for a PPP parameter set Sent to CCL by: "Gustavo L.C. Moura" [gustavo.moura^ufpe.br] Dear CCL Community, For the continuation of my studies on excited states of organic molecules, = I have been looking for a set of Pariser-Parr-Pople parameters. I have already searched on Google and, so far, have not found a PPP paramet= er set that suits my needs. My main problem is with the two-center part of the Hamiltonian. First, I fo= und out that the choice between the Ohno (OH) or the Mataga-Nishimoto (MN) = equations for gamma affect my results a lot. Therefore, I need a parameter = set where the choice between OH or MN equations has already been made. Seco= nd, I would like to have resonance integrals that depend on the distance be= tween the atoms (not a constant as I have found in some places). I will be very grateful if someone out there points me in the right directi= on. Sincerely yours, Gustavo L.C. Moura -=3D This is automatically added to each message by the mailing script =3D-http://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp://www.ccl.net/chemistry/sub_unsub.shtmlhttp://www.ccl.net/spammers.txt--_000_A94E15A372E6194CA8719D62642F674401374B5E80MBX2adrucdk_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Dear Gustavo!
  
Whether you use MN or OH two-center electron repulsion integrals does = not depend so much on the other PPP parameters. The choice depends primaril= y on the configuration interaction (CI) expansion. If the expansion is limi= ted to singly excited configurations (CIS), the strongly screened MN integrals tend to be adequate. But if you = include doubly or higher excited configurations, thereby explicitly introdu= cing terms in electron correlation, the less screened OH integrals are more= appropriate. 

You want to include distance depending resonance integrals (beta's). L= et me just mention that if you include resonance integrals between 'non-bon= ded' centers, thereby abandoning the tight-binding approximation, you break= the spirit of the PPP concept.

Yours, Jens >--<  

------------------------------------------------------
JENS SPANGET-LARSEN              Office:= +45 4674 2710
Dept. of Science                 Fa= x: +45 4674 3011
Roskilde University              Mobile:= +45 2320 6246
P.O.Box 260                   =    Mail: spanget\a/ruc.dk
DK-4000 Roskilde, Denmark  Web: thiele.ruc.dk/~spanget
------------------------------------------------------

________________________________________
Fra: owner-chemistry+spanget=3D=3Druc.dk\a/ccl.net [owner-chemistry+s= panget=3D=3Druc.dk\a/ccl.net] p&#229; vegne af Gustavo L.C. Moura gustavo= .moura(0)ufpe.br [owner-chemistry\a/ccl.net]
Sendt: 12. januar 2019 01:19
Til: Jens Spanget-Larsen
Emne: CCL: Looking for a PPP parameter set

Sent to CCL by: "Gustavo L.C. Moura" [gustavo.moura^ufpe.br]
Dear CCL Community,
For the continuation of my studies on excited states of organic molecules, = I have been looking for a set of Pariser-Parr-Pople parameters.
I have already searched on Google and, so far, have not found a PPP paramet= er set that suits my needs.
My main problem is with the two-center part of the Hamiltonian. First, I fo= und out that the choice between the Ohno (OH) or the Mataga-Nishimoto (MN) = equations for gamma affect my results a lot. Therefore, I need a parameter = set where the choice between OH or MN equations has already been made. Second, I would like to have resona= nce integrals that depend on the distance between the atoms (not a constant= as I have found in some places).
I will be very grateful if someone out there points me in the right directi= on.
Sincerely yours,
Gustavo L.C. Moura



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