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How to get rid of Imaginary Frequencies.....

Siddheshwar Chopra

Dear Sir,
This in regard to my problems with getting rid of imaginary frequencies in the vibrational data. I have tried changing the basis sets, changed the ITOL, ICUT values... Please suggest me what should I do to ge trid of imaginary frequencies?? Currently I am trying out PC-2 basis set. A sample input commands are as follows:

INPUT CARD> $SYSTEM MEMORY=12065831 aoints=dist TIMLIM=525600 KDIAG=1 $END                
INPUT CARD> $CONTRL DFTTYP=B3LYP COORD=UNIQUE NZVAR=132 $END                              
INPUT CARD> $CONTRL MAXIT=10000 MOLPLT=.t. PLTORB=.t. $END                                
INPUT CARD>! $CONTRL EXETYP=CHECK $END                                                    
INPUT CARD> $BASIS GBASIS=N31 NGAUSS=6 NDFUNC=1 NPFUNC=1 $END                              
INPUT CARD> $STATPT opttol=10E-7 NSTEP=200 Method=GDIIS HSSEND=.TRUE. $END                
INPUT CARD> $SMP HTTFIX=.f. $END                                                          
INPUT CARD> $p2p p2p=.t. mxbuf=2048 dlb=.t. $END                                          
INPUT CARD> $SCF dirscf=.t. fdiff= .f. diis=.t. $END                                      
INPUT CARD> $DFT HFX(1)=0.15 $END                                                          
INPUT CARD> $ZMAT DLC=.t. AUTO=.t. $END                                                    
INPUT CARD> $FORCE NVIB=2 $END                          

Please help me.


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