Open-shell calculations in Gaussian involve studying systems with unpaired electrons. Methods like Open-Shell DFT, UHF, and ROHF are used to describe these systems, considering spin properties and stability. Gaussian software offers various density functionals (e.g., B3LYP, BP86) and post-Hartree-Fock methods (e.g., CCSD, MP2) for accurate calculations. Stability analysis assesses the singlet-triplet energy gap, diradical character, and spin contamination to ensure reliable results.
