"Too many spin couplings" error message

[Ioannis Kerkines]

Dear list,

When I try to perform a rather large MRCI calculation on a diatomic
molecule, I get this error:

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1PROGRAM * CI (Multireference internally contracted CI)     Authors: H.-J. Werner, P.J. Knowles, 1987


 Number of optimized states:  1  Roots:   1
 Number of reference states:  1  Roots:   1

 Reference symmetry:               4   Quartet
 Maximum shell in reference space  4
 Maximum shell inside CICON        7

 Maximum number of shells:             7
 Maximum number of spin couplings:  2002

 Reference space:     1857 conf     5008 CSFs
 N elec internal:   119030 conf   698336 CSFs
 N-1 el internal:   113401 conf  1276062 CSFs
 N-2 el internal:    46928 conf   865950 CSFs

 Number of electrons in valence space:                     17
 Maximum number of open shell orbitals in reference space:  9
 Maximum number of open shell orbitals in internal spaces: 15


 TOO MANY SPIN COUPLINGS:  2002 MXSPC=  1001

 ERROR EXIT

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Can I just, by intervening in the source code, change the MXSPC constant,
or this will create further problems?

Thanks in advance,

John Kerkines 
PhD Student
Laboratory of Physical Chemistry
Department of Chemistry
University of Athens, Greece