The standard of accuracy for quantum chemical calculations of thermochemical and chemical kinetics data is 1 kcal/mol (which is equal 4.2 kJ/mol or 1.593•10 -3 hartree). 9, 10 A typical desired accuracy for excitation or ionization energies is 0.01-0.1 eV. The errors in the calculations arise due to the intrinsic errors of the methods due to approximations in many-electron and one-electron bases 1 as well as due to the finite convergence thresholds for the iterative algorithms. Typically, convergence thresholds are much tighter than the methods' error bars.