[molpro-user] Not accurate with MRCI

[Peterson, Kirk]

I would recommend taking a look at the Davidson corrected MRCI results.

regards,

-Kirk

On Jul 24, 2014, at 10:41 AM, samala nagaprasad reddy <snpreddy63 at gmail.com> wrote:

> 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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