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Using first-principles calculations,we systematically study the dissociations of O_2 molecules on different ultrathin Pb(111) films.According to our previous work revealing the molecular adsorption precursor states for O_2,we further explore why there are two nearly degenerate adsorption states on Pb(111) ultrathin films,but no precursor adsorption states existing at all on Mg(0001) and Al(111) surfaces.The reason is concluded to be the different surface electronic structures.For the O_2 dissociation,we consider both the reaction channels from gas-like and molecularly adsorbed O_2 molecules.We find that the energy barrier for O_2 dissociation from the molecular adsorption precursor states is always smaller than that from O_2 gas.The most energetically favorable dissociation process is found to be the same on different Pb(111) films,and the energy barriers are found to be influenced by the quantum size effects of Pb(111) films.
Using first-principles calculations, we systematically study the dissociations of O_2 molecules on different ultrathin Pb (111) films. Accredited to our previous work revealing the molecular adsorption precursor states for O_2, we further explore why there are two near degenerate adsorption states on Pb (111) ultrathin films, but no precursor adsorption states existing at all on Mg (0001) and Al (111) surfaces. The reason is noted to be the different surface electronic structures. For the O 2 dissociation, we consider both the reaction channels from gas-like and molecularly adsorbed O_2 molecules. We find that the energy barrier for O_2 dissociation from the molecular precursor precursor states is always smaller than that from O_2 gas. The most energetically favorable dissociation process is found to be the same on different Pb (111 ) films, and the energy barriers are found to be influenced by the quantum size effects of Pb (111) films.