From owner-chemistry@ccl.net Sun Aug 18 01:06:00 2013 From: "brupalf brupalf|,|umich.edu" To: CCL Subject: CCL: shopping for a practical QM method Message-Id: <-49088-130818010201-32410-vLTdYrR+gURSBNfHUFnERg\a/server.ccl.net> X-Original-From: brupalf Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=us-ascii Date: Sun, 18 Aug 2013 00:56:06 -0400 Mime-Version: 1.0 (Mac OS X Mail 6.5 \(1508\)) Sent to CCL by: brupalf [brupalf]![umich.edu] Hi I'm looking for recommendations for a practical QM method for a series of calculations on a range of related systems consisting of, oh, maybe two-dozen to four-dozen atoms. These systems will be for both closed-shell molecules and the analogous radicals; they will often be charged; the elements will generally be C, H, O, N, and sometimes S; modeling solvent is highly desirable. Key goals for the calculations will be energy differences between systems, the energies and coefficients of HOMO/LUMO/SOMO, partial charges (by whatever scheme), and maybe vibrational frequencies. Would PM7 be appropriate for a series of calculations like this? DFT? Or - what? I'd appreciate any advice. ciao, Bruce From owner-chemistry@ccl.net Sun Aug 18 08:11:00 2013 From: "Dr. Vitaly Chaban vvchaban[A]gmail.com" To: CCL Subject: CCL: shopping for a practical QM method Message-Id: <-49089-130818080941-14680-Wba8RT8Fs7IC+F15N1ShNQ/a\server.ccl.net> X-Original-From: "Dr. Vitaly Chaban" Content-Type: multipart/alternative; boundary=047d7bacc1546667ac04e437b2d8 Date: Sun, 18 Aug 2013 14:08:54 +0200 MIME-Version: 1.0 Sent to CCL by: "Dr. Vitaly Chaban" [vvchaban#,#gmail.com] --047d7bacc1546667ac04e437b2d8 Content-Type: text/plain; charset=ISO-8859-1 Hi Bruce - PM7 is an option, of course. Though for your small systems (...four dozen atoms... still looks pretty small for me) you can afford much better theories. I had many issues when PM7 predicted wrong chemical bonds after geometry relaxation, poorly captured electron delocalization, etc. MP2 will be a bit time consuming, but probably most reliable, if you care about comparison among these systems. If not, than pick up any of the latest hybrid DFT functionals, such as M11, and there are a dozen of alternatives. I did not understand if solvent is included in those four dozen atoms or not. The solvent can be implicit, of course. Dr. Vitaly V. Chaban On Sun, Aug 18, 2013 at 6:56 AM, brupalf brupalf|,|umich.edu < owner-chemistry]^[ccl.net> wrote: > > Sent to CCL by: brupalf [brupalf]![umich.edu] > Hi > > I'm looking for recommendations for a practical QM method for a series of > calculations on a range of related systems consisting of, oh, maybe > two-dozen to four-dozen atoms. These systems will be for both closed-shell > molecules and the analogous radicals; they will often be charged; the > elements will generally be C, H, O, N, and sometimes S; modeling solvent is > highly desirable. Key goals for the calculations will be energy differences > between systems, the energies and coefficients of HOMO/LUMO/SOMO, partial > charges (by whatever scheme), and maybe vibrational frequencies. > > Would PM7 be appropriate for a series of calculations like this? DFT? Or - > what? I'd appreciate any advice. > > ciao, > Bruce> > > --047d7bacc1546667ac04e437b2d8 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Hi Bruce -=A0

PM7 is an opti= on, of course. Though for your small systems (...four dozen atoms... still = looks pretty small for me) you can afford much better theories. I had many = issues when PM7 predicted wrong chemical bonds after geometry relaxation, p= oorly captured electron delocalization, etc.

MP2 will be a bit time consuming, but probably most rel= iable, if you care about comparison among these systems. If not, than pick = up any of the latest hybrid DFT functionals, such as M11, and there are a d= ozen of alternatives.

I did not understand if solvent is included in those four do= zen atoms or not. The solvent can be implicit, of course.


Dr. Vitaly V. Chaban


<= div class=3D"gmail_extra">


On S= un, Aug 18, 2013 at 6:56 AM, brupalf brupalf|,|umich.edu <owner-chemistry]^[ccl.net> wrote:

Sent to CCL by: brupalf [brupalf]![umich.edu]
Hi

I'm looking for recommendations for a practical QM method for a series = of calculations on a range of related systems consisting of, oh, maybe two-= dozen to four-dozen atoms. These systems will be for both closed-shell mole= cules and the analogous radicals; they will often be charged; the elements = will generally be C, H, O, N, and sometimes S; modeling solvent is highly d= esirable. Key goals for the calculations will be energy differences between= systems, the energies and coefficients of HOMO/LUMO/SOMO, partial charges = (by whatever scheme), and maybe vibrational frequencies.

Would PM7 be appropriate for a series of calculations like this? DFT? Or - = what? I'd appreciate any advice.

ciao,
Bruce



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--047d7bacc1546667ac04e437b2d8-- From owner-chemistry@ccl.net Sun Aug 18 20:21:00 2013 From: "Philippe Bourassa philippe.bourassa ~ uqtr.ca" To: CCL Subject: CCL: shopping for a practical QM method Message-Id: <-49090-130818154512-9493-TQG0Wh3ZoJEEHk3aykjpKw,,server.ccl.net> X-Original-From: Philippe Bourassa Content-Type: multipart/alternative; boundary=047d7b604d028610d804e43e0fb4 Date: Sun, 18 Aug 2013 15:45:06 -0400 MIME-Version: 1.0 Sent to CCL by: Philippe Bourassa [philippe.bourassa^-^uqtr.ca] --047d7b604d028610d804e43e0fb4 Content-Type: text/plain; charset=ISO-8859-1 Systems of this size are easily done with DFT methods. 2013/8/18 brupalf brupalf|,|umich.edu > > Sent to CCL by: brupalf [brupalf]![umich.edu] > Hi > > I'm looking for recommendations for a practical QM method for a series of > calculations on a range of related systems consisting of, oh, maybe > two-dozen to four-dozen atoms. These systems will be for both closed-shell > molecules and the analogous radicals; they will often be charged; the > elements will generally be C, H, O, N, and sometimes S; modeling solvent is > highly desirable. Key goals for the calculations will be energy differences > between systems, the energies and coefficients of HOMO/LUMO/SOMO, partial > charges (by whatever scheme), and maybe vibrational frequencies. > > Would PM7 be appropriate for a series of calculations like this? DFT? Or - > what? I'd appreciate any advice. > > ciao, > Bruce> > > --047d7b604d028610d804e43e0fb4 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Systems of this size are easily done with DFT methods.


2013/8= /18 brupalf brupalf|,|umich.edu <o= wner-chemistry_-_ccl.net>

Sent to CCL by: brupalf [brupalf]![umich.edu]
Hi

I'm looking for recommendations for a practical QM method for a series = of calculations on a range of related systems consisting of, oh, maybe two-= dozen to four-dozen atoms. These systems will be for both closed-shell mole= cules and the analogous radicals; they will often be charged; the elements = will generally be C, H, O, N, and sometimes S; modeling solvent is highly d= esirable. Key goals for the calculations will be energy differences between= systems, the energies and coefficients of HOMO/LUMO/SOMO, partial charges = (by whatever scheme), and maybe vibrational frequencies.

Would PM7 be appropriate for a series of calculations like this? DFT? Or - = what? I'd appreciate any advice.

ciao,
Bruce



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--047d7b604d028610d804e43e0fb4-- From owner-chemistry@ccl.net Sun Aug 18 21:58:01 2013 From: "David Gallagher gallagher.da|-|gmail.com" To: CCL Subject: CCL: shopping for a practical QM method Message-Id: <-49091-130818215557-8915-x0kS9c/TtOZFzZzfu5sQeg(0)server.ccl.net> X-Original-From: David Gallagher Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1; format=flowed Date: Sun, 18 Aug 2013 18:55:49 -0700 MIME-Version: 1.0 Sent to CCL by: David Gallagher [gallagher.da : gmail.com] Hi Bruce, I would suggest running some calculations with PM7 and any other methods that are accessible to you, then correlate each set of results with the experimental properties that you are trying to predict. That should enable you to decide which method is most suitable for your needs (speed and accuracy). Good luck, David On 8/17/2013 9:56 PM, brupalf brupalf|,|umich.edu wrote: > Sent to CCL by: brupalf [brupalf]![umich.edu] > Hi > > I'm looking for recommendations for a practical QM method for a series of calculations on a range of related systems consisting of, oh, maybe two-dozen to four-dozen atoms. These systems will be for both closed-shell molecules and the analogous radicals; they will often be charged; the elements will generally be C, H, O, N, and sometimes S; modeling solvent is highly desirable. Key goals for the calculations will be energy differences between systems, the energies and coefficients of HOMO/LUMO/SOMO, partial charges (by whatever scheme), and maybe vibrational frequencies. > > Would PM7 be appropriate for a series of calculations like this? DFT? Or - what? I'd appreciate any advice. > > ciao, > Bruce> > > . >