<div dir="ltr"><div><div>Dear molpro users<br><br><br></div>       I am computing potential energy curve for ground state O2+ at multi level using av5z basis set. This dissociates to O(3P)+O+(4S) fragments. Now I add the energies of these two fragments and get -149.18369960 hartrees at the same level. When I look at the energies of curve at 100 angstrom, the multi value at this long distance is  -149.13557933 hartrees. I wonder why and how this numerical discrepancies arise? My input file is very simple without any complicated keyworkds. Am I missing something relevent to this type of problem? Any suggestion please.<br><br><br></div>My input<br><br> ***,o2+<br> memory,125,m<br> print,orbitals,civector<br>                                                                                 !file,1,o2+_<a href="http://ci_d2h_6_1_mar5.int">ci_d2h_6_1_mar5.int</a><br>                                                                                 !file,2,o2+_ci_d2h_6_1_mar5.wfu<br>                        !symmetry,nosym                                                                                 !symmetry,x<br>                                                         !rcm=[1.11780256,0.7,0.75,0.8,0.85,0.9,0.95,1,1.025,1.05,1.075,1.1,1.110,\<br>                                                                            !      1.125,1.15,1.175,1.2,1.25,1.3,1.35,1.4,1.5,1.6,\<br> !      1.7,1.8,1.9,2,2.125,2.25,2.5,2.75,3,3.25,3.375,3.5,3.625,3.75,4,4.25,4.5,4.75,5,5.25,5.5,5.75,6,6.5,7,7.5,8,9,10,11,12,13,14,15,16,18,20,21,22,23,24,25] ANG<br> rcm=[100] ANG<br><br> geometry                                                                        !geometry specification, using z-matrix<br> o1<br> o2,o1,r<br> end<br><br> basis=aug-cc-pV5Z<br><br> do i=1,#rcm<br><br> r=rcm(i)<br><br> {multi;maxiter,40;config;pspace,0.1;wf,15,7,1;dm}<br> emulti_gs(i)=energy(1)<br>                                                                                 !{ci;option,maxiti=10000;wf,15,6,1}<br>                                                                                 !eci_gs(i)=energy(1)<br>                                                                                 !eci_david(i)=energd(1)<br><br> {table,rcm,emulti_gs<br> Title,Results for O2+ dissociation 2Pi_g state<br> format,'(f15.8,f30.15)'}<br><br>                                                                                 !{table,rcm,eci_gs<br>                                                                                 !format,'(f15.8,f30.15)'}<br><br>                                                                                 !{table,rcm,eci_david<br>                                                                                 !format,'(f15.8,f30.15)'}<br><br> end do<br><br></div>