From owner-chemistry@ccl.net Sat Jul 13 13:38:00 2013 From: "Anon anon+*+example.none" To: CCL Subject: CCL:G: Singlet Dioxygen Optimization Failure at MP2/6-31G Message-Id: <-48952-130712175147-15701-B3Uk0F94odfmehEVJdXY9g:_:server.ccl.net> X-Original-From: Anon Content-Disposition: inline Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1; DelSp="Yes"; format="flowed" Date: Fri, 12 Jul 2013 18:46:39 -0300 MIME-Version: 1.0 Sent to CCL by: Anon [anon**example.none] Frank, What's a good resource where I could look up the ground state for various diatomic molecules such as dioxygen, diboron, dicarbon, NO, SO, etc. ? anon Quoting "Frank Jensen frj^chem.au.dk" : > Just to clarify the recent rant on O2. > The ground state is a triplet, can be run with any of your favorite > single determinant methods. > There are two low-lying singlet states. > The lowest is a singlet delta state. It can be described by a > two-determinant casscf, or a single determinant with complex > orbitals. The latter is an option in Gaussian, and can be done at > the MP2 level. Equilibrium geometry and singlet-triplet splitting is > quite good at this level. > The next excited state is a singlet sigma. You need a 2e-2o casscf > to descrice this. > These are low-lying valence states and basis set requirements are as > usual for 'ground state' systems. > Specifying a singlet (real orbital) determinant will get you a > mixture of the singlet delta and sigma state. Go figure how relevant > that is for your application. > > Frank > > Sendt fra min iPad > > Den 12/07/2013 kl. 03.55 skrev "Bradley Welch > bwelch5[-]slu.edu" > >: > > Singlet Oxygen does in fact exist as an excited state in the oxygen > diatomic molecule. I think the O2 singlet needs to a more powerful > method besides MP2 for an excited state calculation. I ran it > through Gaussian 09 with CCSD(T)/6-311G** and it successfully > completed. You might want to use a more robust basis set depending > on what you are planning on doing, especially for an excited state. > > > On Thu, Jul 11, 2013 at 6:54 PM, Cu Phung > cphung::methodist.edu > > wrote: > Diatomic oxygen is not a singlet state but a triplet state. That is > why it won't optimize. Change the line > 0 1 > to > 0 3 > and it should work. > > CGP > > Sent > from my iPad > > On Jul 11, 2013, at 1:04 PM, "Jiabo Li > jiaboli{=}yahoo.com" > > wrote: > > O2 has a triplet ground state, not singlet. > >> From: "Anon anon,example.none" >> > > To: "Li, Jiabo " > > Sent: Thursday, July 11, 2013 6:54 AM > Subject: CCL:G: Singlet Dioxygen Optimization Failure at MP2/6-31G > > > Sent to CCL by: "Anon" [anon : example.none] > I am trying to optimize singlet dioxygen at the MP2/6-31G level of > theory but it is not working. Increasing the number of optimization > steps does no good either. After the number of steps are used up, I > see that the final length of the unoptimized molecule is about 50 > Angstroms. At each optimization step Gaussian keeps increasing the > bond length, failing to realize that the bond length is much smaller. > > Here is the input that I am using: > > # MP2/6-31G OPT > > 0 1 > O > O 1 R1 > > R1=1.2 > > Could someone add any insight to this issue? Why can't I optimize > dioxygen, which is such a simple molecule? Can a specific keyword > help this problem? > > > > -= This is automatically added to each message by the mailing script > =-the strange characters on the top line to the (_) sign. You can also > E-mail to subscribers: > CHEMISTRY(_)ccl.net or use: > = > > E-mail to administrators: > CHEMISTRY-REQUEST(_)ccl.net or > usehttp://www.ccl.net/chemistry/sub_unsub.shtmlhttp://www.ccl.net/spammers.txt-- > Bradley Welch > Saint Louis University > Monsanto Hall Room 218 > From owner-chemistry@ccl.net Sat Jul 13 16:11:00 2013 From: "Susi Lehtola susi.lehtola ~~ alumni.helsinki.fi" To: CCL Subject: CCL: Singlet Dioxygen Optimization Failure at MP2/6-31G Message-Id: <-48953-130713150528-7762-hu6BHzHogYtQLFK7sMR7hg-$-server.ccl.net> X-Original-From: Susi Lehtola Content-Disposition: inline Content-Type: text/plain; charset=UTF-8; format=flowed; DelSp=Yes Date: Sat, 13 Jul 2013 22:05:17 +0300 MIME-Version: 1.0 Sent to CCL by: Susi Lehtola [susi.lehtola%alumni.helsinki.fi] Quoting "Anon anon+*+example.none" : > Sent to CCL by: Anon [anon**example.none] > Frank, > > What's a good resource where I could look up the ground state for > various diatomic molecules such as dioxygen, diboron, dicarbon, NO, > SO, etc. ? The NIST Chemistry Webbook has loads of information for diatomic molecules. Just search on http://webbook.nist.gov/chemistry/form-ser.html and click on "Constants of diatomic molecules." -- --------------------------------------------------------------- Mr. Susi Lehtola, PhD Postdoctoral researcher susi.lehtola[#]alumni.helsinki.fi Department of Applied Physics http://www.helsinki.fi/~jzlehtol Aalto University Finland --------------------------------------------------------------- Susi Lehtola, FT Tutkijatohtori susi.lehtola[#]alumni.helsinki.fi Fysiikan laitos http://www.helsinki.fi/~jzlehtol Aalto-yliopisto ---------------------------------------------------------------