why casscf not converge in an opt calculation in molpro



Dear chemistry#:
 In molpro calculations with casscf, I found a puzzle.
 If omit the "optg" from the input file below, the casscf calculation
 will converge.
 If use the "optg", the casscf calculation will not converge.
 If use "frequencies" instead of "optg", the casscf
 calculation will also not converge.
 Why?
 **** CO2 scan
 r1=1.2 Ang
 geometry
 C
 O1 ,C, r1
 O2 ,C, r1, O1,180
 end
 gprint,basis,orbitals
 basis
 spd,c,vdz;c
 spd,o,vdz;c
 end
 hf
 casscf
 optg
     Thank you for your help!
 Yours sincerely,
 Ding Xunlei
 2005-07-07
 ______________________________________________