From owner-chemistry # - at - # ccl.net Fri Jul 6 12:04:00 2007 From: "errol lewars elewars]^[trentu.ca" To: CCL Subject: CCL:G: Basis sets with B3LYP Message-Id: <-34680-070706091825-9791-ItWG7Zx/wQL/p5x9Oqw60A#%#server.ccl.net> X-Original-From: errol lewars Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii; format=flowed Date: Fri, 06 Jul 2007 09:18:33 -0400 MIME-Version: 1.0 Sent to CCL by: errol lewars [elewars=trentu.ca] 2007 July 6 Occasionally a structure will oscillate on attempted geometry optimization because the initial hessian is unsatisfactory. For example, starting with an AM1 geometry for equatorial t-butylcyclohexane an attempted B3LYP/6-31G* opt failed with an MNDO hessian, but using a molecular mechanics hessian an optimized geometry was quickly obtained. Of course there are other sources of oscillation problems. E. Lewars ==== Michael Edmund Miller mill*|*pica.army.mil wrote: >Sent to CCL by: "Michael Edmund Miller" [mill- -pica.army.mil] >Dear all, >In gaussian 03, I am trying to run a B3LYP/6-31g(d) optimization of an open-ended nanotube consisting of 68 carbon and 2 boron atoms. Using HF optimized coordinates, I am not able to optimize at 6-31g(d) or even 3-21g using B3LYP (It appears to me that energy oscillations are occurring; also, as Gaussview shows me, the structure moves away from the local minimum and is not intact after a number of iterations). HOWEVER, I can optimize using STO-3G within B3LYP! The STO-3G optimized coordinates are as follows: > > >Optimization of C68B2 singlet using B3LYP/STO-3G optimized coor. > >0 1 >C1 -0.359613 -2.837234 0.030572 >C2 -1.822764 -2.846306 0.021630 >C3 0.366023 -2.620439 1.264848 >C4 0.350332 -2.550359 -1.206821 >C5 -2.572745 -2.552803 1.249363 >B1 -0.375396 -1.828130 2.322287 >C6 -2.515863 -2.555305 -1.210819 >C7 -0.360745 -1.763614 -2.198134 >C8 1.798604 -2.554804 -1.215518 >C9 1.809377 -2.575825 1.244195 >C10 -1.894237 -1.797746 2.269146 >C11 0.367210 -0.624769 2.877461 >C12 -1.805928 -1.767020 -2.205730 >C13 0.358588 -0.630281 -2.747865 >C14 -4.071224 -2.533801 1.193287 >C15 -3.998586 -2.567003 -1.250738 >C16 2.522275 -1.761316 2.238739 >C17 2.521863 -2.833380 0.014918 >C18 2.510926 -1.765512 -2.198179 >C19 -2.582264 -0.638069 2.778289 >C20 -0.358588 0.630179 -2.747888 >C21 -2.520623 -0.632966 -2.753789 >C22 -0.367210 0.624875 2.877438 >C23 -4.684785 -2.925720 -0.043346 >C24 -4.692631 -1.777887 2.221492 >C25 -4.630420 -1.828206 -2.301963 >C26 4.007116 -1.781453 2.215869 >C27 1.828055 -0.619929 2.820655 >C28 4.011574 -2.834800 -0.009767 >C29 3.992633 -1.774873 -2.217515 >C30 1.804093 -0.630848 -2.750662 >C31 -1.804093 0.630747 -2.750686 >C32 0.360745 1.763533 -2.198200 >B2 0.375396 1.828216 2.322219 >C33 -1.828055 0.620033 2.820632 >C34 -4.079738 -0.603691 2.731481 >C35 -4.007741 -0.627743 -2.767577 >C36 4.613723 -2.673463 1.272282 >C37 4.658889 -2.630781 -1.273259 >C38 4.626844 -0.662011 -2.854232 >C39 2.520624 0.632864 -2.753812 >C40 2.582264 0.638172 2.778266 >C41 4.694009 -0.685756 2.827634 >C42 -0.350332 2.550314 -1.206915 >C43 -0.366023 2.620486 1.264751 >C44 -2.510926 1.765430 -2.198245 >C45 -2.522275 1.761399 2.238674 >C46 -4.626844 0.661905 -2.854257 >C47 -4.694008 0.685860 2.827609 >C48 4.007741 0.627641 -2.767600 >C49 1.805928 1.766938 -2.205795 >C50 4.079738 0.603792 2.731458 >C51 1.894237 1.797830 2.269080 >C52 -1.798604 2.554758 -1.215613 >C53 0.359613 2.837235 0.030467 >C54 -1.809377 2.575871 1.244100 >C55 -3.992633 1.774791 -2.217581 >C56 -4.007116 1.781536 2.215803 >C57 4.630419 1.828121 -2.302030 >C58 2.515863 2.555260 -1.210914 >C59 2.572745 2.552850 1.249268 >C60 4.692630 1.777969 2.221426 >C61 -2.521863 2.833381 0.014814 >C62 -4.658889 2.630734 -1.273356 >C63 -4.613724 2.673510 1.272183 >C64 3.998586 2.566957 -1.250833 >C65 4.071224 2.533846 1.193193 >C66 1.822764 2.846307 0.021525 >C67 -4.011574 2.834800 -0.009871 >C68 4.684786 2.925718 -0.043455 > > > >Any comments/assistance on why a minimal basis set works, and yet all the split basis sets I've tried do not? >Thank you. >Mike> > > > >