The lower the ĪS,min, the larger in magnitude is the chemisorption energy, i.e., the more reactive is the carbon. From Fig. 4, it is seen that the hydrogen chemisorption energies become more negative as ĪS,min decreases. As is also evident, we find an acceptable correlation (R2¼0.981) between evaluated ĪS,min and hydrogen chemisorption energies at the sites of the carbon atoms.