[molpro-user] Not accurate with MRCI

[samala nagaprasad reddy]

Dear Sir,
I want to calculate the ionization values of Diacetylene using MRCI.
To define the degeneracy I am using ref keyword. But my values are not
accurate, even I have tried with different active space. The ionizations
getting from OVGF (using gaussin03) seems better than the MRCI data.
Here I am giving the methods and results in eV.

method      IP1/IP2 (degenerate)    IP3/IP4 (degenerate)            IP5
OVGF           10.105
12.623                              17.332
MRCI(8,8)     10.010
12.584                              24.279
MRCI(12,10)  10.006                           12.600
                             18.299
MRCI(10,9)    10.040                           12.632
                             18.2992
MRCI(12,11)  10.009                           12.602
                             18.183
 experiment    10.17
12.62                                 16.61

First two IPs are in good agreement with experiment. Why I am getting large
variation in case of IP5. Please suggest me to improve the IP5 value with
experiment.

Here I am giving my MRCI (8,8) input file for better understanding

 ***,coupling constants
 memory,400,m
 basis,avtz
 geomtyp = xyz
 geometry = {6,
 planar isomer
 C                     0.000000    0.000000    1.904717
 C                     0.000000    0.000000    0.684532
 H                     0.000000    0.000000    2.967194
 C                     0.000000    0.000000   -0.684532
 C                     0.000000    0.000000   -1.904717
 H                     0.000000    0.000000   -2.967194
 end}
 {rhf;occ,5,1,1,0,4,1,1,0;wf,26,1,0;}
 {multi;occ,6,2,2,0,5,1,1,0;closed,5,0,0,0,4,0,0,0;wf,26,1,0;}
 {mrci;occ,6,2,2,0,5,1,1,0;closed,5,0,0,0,4,0,0,0;wf,26,1,0;}
 {mrci;occ,6,2,2,0,5,1,1,0;closed,5,0,0,0,4,0,0,0;wf,25,2,1;ref,3;}
 {mrci;occ,6,2,2,0,5,1,1,0;closed,5,0,0,0,4,0,0,0;wf,25,3,1;ref,2;}
 {mrci;occ,6,2,2,0,5,1,1,0;closed,5,0,0,0,4,0,0,0;wf,25,6,1;ref,7;}
 {mrci;occ,6,2,2,0,5,1,1,0;closed,5,0,0,0,4,0,0,0;wf,25,7,1;ref,6;}
 {mrci;occ,6,2,2,0,5,1,1,0;closed,5,0,0,0,4,0,0,0;wf,25,1,1;state,2;}


Please suggest me to improve the ionization numbers.
Thank you in advance
Nagaprasad Reddy.
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