multiplicity problem in open-shell dft


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Gets Around
Hi.
I am a beginner in nwchem.
I was trying to calculate interaction between two monomers using open-shell DFT. The input script i was using:
title 'dft-energy'
start dimer
geometry units angstrom
  symmetry c1  
  C 2.965 23.359 58.764
  C 1.892 22.522 58.067 
  O 2.178 21.539 57.399 
  C 3.074 22.934 60.212 
  C 4.384 23.352 60.901  
  N 4.641 24.608 61.248  
  C 5.423 22.607 61.249 
  C 5.863 24.629 61.854  
  N 6.338 23.431 61.871  
  H 3.814 23.193 58.326  
  N 2.739 24.753 58.631 
  H 2.603 25.170 59.371  
 O 2.533 26.305 61.093  
 C 2.375 27.069 62.059  
 N 0.276 24.751 62.891  
 C 0.008 26.050 62.356  
 C -0.203 26.009 60.830 
 O -0.082 24.982 60.186 
 C 1.059 27.102 62.775  
 O 3.249 27.900 62.464  
 H 1.049 24.613 63.117  
 H -0.829 26.341 62.751 
 H 0.671 27.982 62.652  
 H 1.229 26.997 63.724    
end

charge 0

basis "ao basis"   
  * library 6-31G   
  bq* library * 6-31G
end

dft
  odft      
  xc pbe0
  direct
  iterations 700
end 

bsse
  mon first 1 2 3 4 5 6 7 8 9 10 11 12 
  mon second 13 14 15 16 17 18 19 20 21 22 23 24 
end
task dft energy


Now the default the multiplicity assigned here is 1. So, I am getting this error:

Summary of "ao basis" -> "ao basis" (cartesian)
 ------------------------------------------------------------------------------
       Tag                 Description            Shells   Functions and Types
 ---------------- ------------------------------  ------  ---------------------
 C                           6-31G                   5        9   3s2p
 O                           6-31G                   5        9   3s2p
 N                           6-31G                   5        9   3s2p
 H                           6-31G                   2        2   2s


  Caching 1-el integrals 
  number of electrons :                   67
  multiplicity        :                    1
 ------------------------------------------------------------------------
  no. of electrons and multiplicity not compatible                  67
 ------------------------------------------------------------------------
 ------------------------------------------------------------------------
  current input line : 
    49: task dft energy
 ------------------------------------------------------------------------
 ------------------------------------------------------------------------
 There is an error in the input file
 ------------------------------------------------------------------------


I am really getting nowhere to perform this calculation with it.
Do I have to define multiplicity for each monomer, as the no. of electrons are different ?
Is it possible that nwchem automatically assign multiplicity ?
Please help.
Thank you.