| 摘要: | 在我們的研究中，我們採用Vienna Ab intio Simulation Package (VASP)去計算N2在W(111)表面上的吸附和加氫反應。計算結果表明N2吸附在W(111)表面有三種可能的結構位置。分別為WN2(T-η1-N), WN2(T,S-μ2-N,N)和WN2(T,T-μ2-N,N)。其中最穩定的結構是WN2(T,T-μ2-N,N)的位置，其吸附能為-22.44 kcal/mol。在第一個加氫的步驟，我們考慮兩種可能的途徑：第一種是N2在氫化前直接分離，第二種是將N2氫化後再分解，我們的計算結果表明，該反應將有利於第二種路徑。在第二次加氫的步驟中，我們發現形成NHHN會有最低的活化能，然而N2H2的NN斷線的較低的活化能也在我們的計算觀察中。從能量的角度來看，我們可以得到NHHN將分裂成兩個NH分子這樣的結果。最後我們還計算了W(111)表面的電子密度分佈(Electron Localization Function ELF) 其結果可以解釋我們的預測有利於吸附結構的方向。為了獲得更多的催化過程的見解，吸附物和基材之間的相互作用性質通過詳細的電子分析來分析。
In our studies, we employed Vienna Ab intio Simulation Package (VASP) to calculate the N2 adsorption and hydrogenation on W(111) surface. The calculated results show that the possible coordinates of three isomers for the N2 adsorption on W(111) are WN2(T-η1-N), WN2(T,S-μ2-N,N) and WN2(T,T-μ2-N,N), respectively. Among them, the most stable structure is WN2(T,T-μ2-N,N) with the adsorption energy of -22.44 kcal/mol. For the first hydrogenation process, we consider two possible pathways: the first one is the direct dissociation of N2 before the hydrogenation, the second one is the hydrogenation of N2 before its dissociation. Our calculated results show that the reaction will favor the second pathway. In the second hydrogenation process, it is found that the formation of HNNH fragment will possess the lowest activation barrier. However, the lower activation barrier of N-N bond scission of N2H2 is also observed in our calculation. Based on the energy point of view, we could conclude that the HNNH would dissociate to two NH fragments. Finally, we also study Electron Localization Function (ELF) of W(111) surface, and the results can explain our predicted orientations of favorable adsorption structures. To gain more insights into catalytic processes of the aforementioned conducts, the interaction nature between the adsorbate and substrate is analyzed via detailed electronic analysis. |
