<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Dear Prof. Grein,<div class=""><br class=""></div><div class="">I ran through the CASSCF part of your input with orbital printing turned on. At 2.7 Ang. one of the O 2p orbitals becomes exactly doubly occupied and for some reason gets swapped with a core orbital (3.1 and 4.1). This persists out to your longest bond length. So the simple fix is to do a orbital rotation in the rs2 or mrci to swap these orbitals back into the correct order from 2.7 onwards:</div><div class=""><br class=""></div><div class="">if (ir2.lt.8) then</div><div class=""><div lang="EN-CA" link="blue" vlink="purple" class=""><div class="WordSection1"><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-US" class=""> {rs2;wf,24,1,0;maxit,100;option,maxiti=400}<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-US" class="">else</span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-US" class=""> {rs2;wf,24,1,0;maxit,100;option,maxiti=400;rotate,3.1,4.1}<o:p class=""></o:p></span></div></div></div></div><div class=""><div lang="EN-CA" link="blue" vlink="purple" class=""><div class="WordSection1"><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-US" class="">endif</span></div></div></div></div><div class=""><br class=""></div><div class="">This is a little strange to me since when orbitals are exactly doubly occupied in multi, Molpro used to canonicalize the closed-shell space.</div><div class=""><br class=""></div><div class="">best regards,</div><div class=""><br class=""></div><div class="">-Kirk</div><div class=""><br class=""></div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Aug 10, 2015, at 5:43 AM, Fritz Grein <<a href="mailto:fritz@unb.ca" class="">fritz@unb.ca</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">
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<div class="WordSection1"><p class="MsoNormal"><span lang="EN-US" class="">Dear MOLPRO users,<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">I am encountering a problem with dissociation to a higher dissociation channel.
<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">When dissociating O3 to O2+O, in 1-A’ symmetry, then the MOLPRO calculated CI energy (for fixed O-O distance and angle), is fine up to an O2-O separation of 2.6 A. Until here, the energy is close to the dissociated O2(3-Sigg)
+ O(3-P) energy. At 2.7 A, the calculated energy jumps higher, and stays higher thereafter. It appears that the O2(1-Delta) + O(1-D) level is approached.
<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">This happens with all CI methods, RS2, MRCI, AQCC and ACPF. Interestingly, the CASSCF energy dissociates to the lowest channel. Dissociation in symmetries, like 1-A”, also moves to a higher channel, although at a larger
distance. <o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">Reading the literature, there are several MOLPRO calculations described for the 1-A’ dissociation of ozone, covering a large potential energy surface. Apparently, no dissociation problems as described above have been
encountered. This means that there must be a way to avoid this problem.<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">Any help would be appreciated. <o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">Fritz Grein<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-CA" class="">Department of Chemistry<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-CA" class="">University of New Brunswick, Canada</span><span lang="EN-US" class=""><o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">--------------------------------------------------------------------<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class=""> R2 ECAS ERS2<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class=""> 2.0 -224.5573513 -225.1020581<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class=""> 2.1 -224.5596135 -225.1015510<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class=""> 2.2 -224.5614908 -225.1012356<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class=""> 2.3 -224.5629154 -225.1009875<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class=""> 2.4 -224.5639408 -225.1007287<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class=""> 2.5 -224.5646529 -225.1003953<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class=""> <b class="">2.6 -224.5651329 -225.0997375<o:p class=""></o:p></b></span></p><p class="MsoNormal"><b class=""><span lang="EN-US" class=""> 2.7 -224.5654847 -225.0134963<o:p class=""></o:p></span></b></p><p class="MsoNormal"><span lang="EN-US" class=""> 2.8 -224.5656828 -225.0134413<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class=""> 2.9 -224.5658012 -225.0133640<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class=""> 3.0 -224.5658675 -225.0132738<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class=""> </span></p><p class="MsoNormal"><span lang="EN-US" class="">***,o3-scan1<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">memory,100,m<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">symmetry,x<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">angstrom<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">geometry={o1<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class=""> o2,o1,r1<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class=""> o3,o2,r2(i),o1,a}<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">r1=1.22,a=120.<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">basis=avtz<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">distance2=[2.0,2.1,2.2,2.3,2.4,2.5,2.6,2.7,2.8,2.9,3.0]<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">i=0<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">do ir2=1,#distance2<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">i=i+1<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">r2(i)=distance2(ir2)<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">{hf;maxit,100}<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">{casscf;wf,24,1,0;maxit,40}<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">ecas(i)=energy<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">{rs2;wf,24,1,0;maxit,100;option,maxiti=400}<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">ers2(i)=energy<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">enddo<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">{table,r2,ecas,ers2<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">head,r2,ecas,ers2}<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class="">----------------------------------------------------------------------<o:p class=""></o:p></span></p><p class="MsoNormal"><span lang="EN-US" class=""> <o:p class=""></o:p></span></p><p class="MsoNormal"><o:p class=""> </o:p></p><p class="MsoNormal"><o:p class=""> </o:p></p><p class="MsoNormal"><o:p class=""> </o:p></p>
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