Density Functional Theory Study On The Interaction Between Hydrogen Atom And Fe(111)

Hydrogen is considered to be an ideal fuel.As an important industrial chemical,hydrogen is a recognized clean fuel because it does not generate combustion products that are harmful to the environment.In the catalytic reactions such as the Fischer-Tropsch reaction and the ammonia synthesis reaction,the interaction between the hydrogen atom and the Fe(111)surface with high catalytic activity is very important for the catalytic reaction.Hydrogen atom adsorption on the surface of transition metals has attracted increasingly attention due to its huge industrial value and economic significance of these catalytic reactions.Periodic slab model calculations based on density functional theory(DFT)have become an effective tool for studying the adsorption of atoms and small molecules on metal surfaces.In this thesis,we first use the plane wave calculation method based on DFT to test the structural parameters of body-centered cubic(bcc)bulk Fe atoms to obtain reasonable optimization settings.We performed surface optimization,parameter testing and surface energy calculation on the periodic slab model of Fe(111)surface cell,and determined the 7-layer surface slab model.Then comparing the adsorption structure of hydrogen atoms on the rigid surface of Fe(111)and the flexible surface,it is found that the relaxation effect of the metal surface is mainly concentrated on the upper three layers of the surface.At the same time,it is found that the order of the stable adsorption sites of hydrogen atoms on Fe(111)surface is Bridge>Hcp>Fcc>Top.The relaxation effect of the metal surface has no significant effect on the hydrogen atom adsorption structure,and the surface spacing and adsorption energy change little.On the Fe(111)surface,we mainly choose three different functionals,and then combine different dispersion correction methods to calculate the relative energy of hydrogen atoms at the four main adsorption sites within a certain distance perpendicular to the surface.It is found that it is reasonable to choose different functional and dispersion correction methods,but there are subtle differences in the description of the system drawn by the scanning curves.We believe that this understanding is essential for future research on the rational design of surface catalysis models for other complex molecules with decomposable hydrogen atoms.In this paper,the nucleophilic reaction mechanism of 5-Br-1,2,3-triazine is studied theoretically,and the nucleophilic aromatic substitution reaction(S_NAr)mechanism of phenol anion and phenol with 5-Br-1,2,3-triazine is discussed.The actual reaction path is that the oxygen atom of phenol anion attacks the C5 position of 5-Br-1,2,3-triazine.The possibility of a synergistic S_NAr reaction between 5-Br-1,2,3-triazine and a suitable nucleophile is confirmed in conjunction with organic experiments.