[molpro-user] Error in atomic MRCI calculation

[Lorenzo Lodi]

Consider the following minimalist calculation for the 3P ground term of
Ar++:

*** Calculation for Ar++

basis={default, cc-pVDZ}
NOSYM
geometry={Ar}

{CASSCF; OCC, 9; CLOSED,5; FROZEN,0; WF, elec=16, sym=1,spin=2;state,3;}
{MRCI    ; OCC, 9; CLOSED,5; CORE,5; WF, elec=16, sym=1,spin=2;state,3; }

CASSCF runs without problems and gives E=-526.817022986694.
MRCI also runs and gives a MRCI energy E=-526.92881183. However, in many
places I get `infinities', e.g.:



 Energy contributions of singly external configurations for state 1
 ==================================================================

   NUMBER        NORM          ECORR1        OCCUPATION

     1       0.00000000      -Infinity      
1022                           
     2       0.00000000      +Infinity      
0122                           
     5       0.00236458      -Infinity      
1220                           


 Energy contributions of configuration classes

 CLASS          SQ.NORM        ECORR1        ECORR2
 +++++++++++++++++++++++++++++++++++++++++++++++++++
 Internals     +Infinity           NaN           NaN
 Singles       +Infinity     -Infinity           NaN
 Pairs         +Infinity     +Infinity           NaN
 Total         +Infinity           NaN           NaN
 +++++++++++++++++++++++++++++++++++++++++++++++++++


 Reference energy                    -526.81702299
 Nuclear energy                         0.00000000
 Kinetic energy                       525.51796052
 One electron energy                 -711.13604804
 Two electron energy                  184.20723620
 Virial quotient                       -1.00268469
 Correlation energy                    -0.11178885
 !MRCI STATE 1.1 Energy              -526.928811837479

 !MRCI STATE 1.1 Dipole moment          0.00000000     0.00000000    
0.00000000
 Dipole moment /Debye                   0.00000000     0.00000000    
0.00000000

 Cluster corrected energies              -Infinity (Davidson, fixed
reference)
 Cluster corrected energies          -526.93344888 (Davidson, relaxed
reference)
 Cluster corrected energies          -526.93344888 (Davidson, rotated
reference)



If I do the MRCI calculation for one state only I obtain slightly larger
energies (E(MRCI)=-526.928597650037) but no `infinities' in the output.
What causes this problem? Is it because I'm running without point-group
symmetry?

Any input would be appreciated :)

Regards,
Lorenzo