[Wien] Error in nn of a supercell

[panzhijun2002 at sjtu.edu.cn]

Hi,everyone:
   After creating a supercell for original CoSi.struct,nn command is performed in the command line.Later on,error follows.The error information is as follows:
   please specify nn-bondlength factor: (usually=2)
   ERROR IN OPENING NN.DEF !!!!
   FORTRAN STOP NN.DEF

 How to solve this problem?Please help me.Thank you very much.