# [molpro-user] Convergence Problem in MCSCF Calculations

Sunil sunil.phys at gmail.com
Mon Jan 26 05:46:37 GMT 2009

```Dear Sir,

I am facing a convergence problem when using Molpro to calculate potential
energy surfaces of CO2 molecule. The input of the program is as follows:

*** CO2 PE curve                        ! Title: PE Curve for CO2
memory,32,m
maxiter=100
geomtyp=zmat
geometry
ang                                     ! ang is used if we intend to
provide distance in Angstrom; default for Z-matrix is au
C
O1 C rco1(i)
O2 C rco2(i) O1 oco
end

r1(1) = 0.400000 Ang
r2(1) = 0.400001 Ang
dr = 0.1 Ang
do i = 1,19
r1(i+1) = r1(i)
r2(i+1) = r2(i) + dr
enddo

oco = 180 Deg

basis = vqz                             ! Basis set specification

do i = 1,20

rco1(i) = r1(i)
rco2(i) = r2(i)

hf;
enhf(i)=energy

mp2;
enmp2(i)=energy

multi;
emcscf(i) = energy

enddo

table rco1,rco2,enhf,enmp2,emcscf               !emscf          !,ecas,emrci
head R1,R2,SCF,MP2,MCSCF
save co2_mcscf.tab
Title Results for CO2 (Angle = 180 Deg)
!sort 3,1,2
---

It produces the output but without convergence for the MCSCF calculations.

Thank you in advance for any kind of help.

regards
Sunil
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