# [molpro-user] Size consistency issue

george george.iitm at gmail.com
Wed Feb 10 19:36:16 CET 2016

```Dear molpro users

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.

My input

***,o2+
memory,125,m
print,orbitals,civector

!file,1,o2+_ci_d2h_6_1_mar5.int

!file,2,o2+_ci_d2h_6_1_mar5.wfu

!symmetry,nosym
!symmetry,x

!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,\

!      1.125,1.15,1.175,1.2,1.25,1.3,1.35,1.4,1.5,1.6,\
!
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
rcm=[100] ANG

geometry
!geometry specification, using z-matrix
o1
o2,o1,r
end

basis=aug-cc-pV5Z

do i=1,#rcm

r=rcm(i)

{multi;maxiter,40;config;pspace,0.1;wf,15,7,1;dm}
emulti_gs(i)=energy(1)

!{ci;option,maxiti=10000;wf,15,6,1}

!eci_gs(i)=energy(1)

!eci_david(i)=energd(1)

{table,rcm,emulti_gs
Title,Results for O2+ dissociation 2Pi_g state
format,'(f15.8,f30.15)'}

!{table,rcm,eci_gs

!format,'(f15.8,f30.15)'}

!{table,rcm,eci_david

!format,'(f15.8,f30.15)'}

end do
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```