Ideally, all minima on PES should be produced by multidimensional (3N-6) scanning of all coordinates at the most accurate QM levels. Otherwise, systematic evaluation of all possible conformers at the most accurate level is required to get insight into the global minimum and all local minima along with their relative energies and populations. Since there are energy barriers among different minima on PES and minimization algorithms using energy gradient (i.e., minimizing energy with respect to coordinate) approach only finds the nearest minimum at which the energy gradient (force) reaches to the zero-threshold. Thus, extensive search with different initial conformations is still required to locate all minima.