For practical reasons, one has to balance the calculation cost and accuracy, as hundreds of thousands of configurations are often computed for developing a reliable full-dimensional PES. For small-size molecular systems, generally coupled cluster and configuration interaction theories 54 associated with reasonable size of basis sets are employed as they can effectively provide reliable electronic energies of configurations spanned in the dynamically relevant regions. Particularly, the coupled cluster approach with single, double, and perturbative triple excitations, CCSD(T), is well recognized as the gold standard for quantum chemistry, as it can provide results of chemical accuracy for a medium sized molecular system at a reasonable calculation cost. For a specific molecular system, ample relevant experimental and theoretical investigations have been often reported for the equilibrium geometries and harmonic frequencies of reactants, products and intermediates, reaction energies or enthalpies, reaction profile, as well as kinetics that is related to the barrier height and the microscopic reaction mechanism. Therefore, the properties of all stationary points (geometries, energies, harmonic frequencies) can be evaluated first by various electronic structure methods. A quick comparison can be made to guide the choice of the electronic structure method.