where the sum extends over all triple pairs of atoms ABC in the system. The damping function is described by geometric average radii r ABC of the system. The computational cost does not rise to higher orders even after the inclusion of D3 correction as it is majorly contributed by the time required to solve the Kohn-Sham equations. Though D3 improves the description of weak interactions for non-covalently bound complexes and metallic systems compared to D2, both of these methods have been prevailingly used for ORR studies. On the contrary to the semi-empirical methods, van der Waals density functionals (vdw-DF) include a non-local correction term incorporated to the exchange correlational functional, which can be represented as,