HCN在Ni(111),Ni(100)和Ni(110)面吸附的密度泛函理论研究

Density Functional Theory Study HCN Adsorption on the Ni(111),Ni(100) and Ni(110)

针对乙腈加氢反应机理的研究,采用密度泛函方法计算了HCN在Ni(111),Ni(100)和Ni(110)表面上的吸附,并在1/4覆盖度的基础上讨论了表面吸附结构及吸附能.结果表明:在Ni(111)面,最稳定的吸附构型为HCN分子中C-N键,几乎平行吸附在表面上,其吸附结构为f-η3(N)-h-η3(C),吸附能为1.369eV.在Ni(100)上,最优吸附构型为HCN吸附在表面上的fcc位,其中C-N键与4个相邻的Ni原子成键,吸附能为1.932eV.在Ni(110)上,HCN吸附构型与其它两个表面相类似,位于两个long-bridge位,其吸附能为1.780eV.同时,也通过电子电荷及态密度分析了HCN在Ni(111),Ni(100)和Ni(110)表面上的成键机理,表明吸附的HCN在表面上已重新杂化,形成了非线性弯曲的吸附结构,这更有利于加氢反应的发生.

The adsorption of HCN on the Ni(111),Ni(100) and Ni(110) surface at the 1/4 monolayer(ML) coverage had been carried out at the level of density functional theory for understanding hydrogenation processes of nitriles.The most favored adsorption structure for HCN on Ni(111) is the C-N bond almost parallel to the surface with the C-N bond interaction with adjacent surface Ni atoms(f-η3(N)-h-η3(C)).The adsorption energy is 1.369 eV.For Ni(100),the most stable configuration is the HCN locates at the fcc site with the C-N bonded to four Ni atoms,and the adsorption energy is 1.932 eV.In Ni(110),the HCN adsorption has been computed,and the adsorption pattern is nearly similar to the HCN on Ni(111) and Ni(100),respectively.The HCN locates at the two long-bridge sites and the energy is 1.780 eV.Furthermore,the binding mechanism of HCN on the Ni(111),Ni(100) and Ni(110) surface is also analyzed.The result is that the adsorbed molecules re-hybridized on the surfaces,becoming non-linear with a bent H-C-N angle.This is more conducive to the occurrence of the hydrogenation reaction.