Chemshell and orca combined for QM / MM calculation. Atomic number in QM is 34.The total number of atoms is 11900. Frequency calculation shows:ORCA finished by error termination in SCF Hessian.

The frequency keywords is the same as the keyword of the optimization calculation.I tried different keywords.But failed.These are the keywords I tried:

1.# Orca input file generated by ChemShell

! O3LYP def2-SVP RIJCOSX def2/J Grid4 TightSCF freq Engrad

%pointcharges "pointcharges.xyz"

%maxcore 3000

%scf MaxIter 500 end

%pal nprocs 14 end

%scf Guess MORead MOInp "save.gbw" end %coords CTyp xyz

Charge 0 Mult 3 Units bohrs coords

2.O3LYP def2-SVP RIJCOSX def2/J gridx4 Grid4 TightSCF freq

3.O3LYP def2-SVP RIJCOSX def2/J Grid5 FinalGrid6 GridX8 NoFinalGridX TightSCF freq

4.O3LYP def2-SVP RIJCOSX def2/J gridx4 Grid6 NoFinalGrid VeryTightSCF freq