In DFT calculation, when is Calc_hess needed?

Hi. I am new to DFT and using ORCA to run calculations of IR and NMR spectra for small (around 30 atoms) organic molecules. I am using and input like: ! M062X TZVP def2/J def2/JK RIJCOSX GridX4...

19 October 2020 1,754 2 View