Study The CH₃CN And CH₃NC On The Surfaces Of Ni By Density Functional Theory

Adsorption is an inevitable and basic step in heterogeneous catalyticreactions.And the catalysts can not speed the reaction until they can chemicallyadsorb the reactants.So the mechanism of catalytic hydrogenation of nitriles isconsidered to start from the adsorption and dissociation of nitriles on the surfaceof catalysts,and such course has already been determined as the reaction ratecontrol step of catalytic hydrogenation of nitriles.the Ni is the importanttransition metal catalysts and has already been extensively used in catalyticreactions in recent years.Exploring the adsorption of CH₃CN and CH₃NC on thesurface of Ni will have great significance for the study on the mechanism oftransition metal catalysis and the improvement of properties of catalyst.Researchcontents as follows：（1） Twenty-four kinds of adsorption CH₃CN on the Ni（111）,Ni（100） andNi（110） surfaces at the1/4monolayer coverage are found using the densityfunctional theory.For Ni（111）,the most favored adsorption structure for CH₃CNon Ni（111） is f-η3（N）-h-η3（C）,in which the C≡N bond is almost parallel to thesurface,and the adsorption energy is-1.117eV.on the Ni（100） surface,theadsorption energy of the most stable configuration where the CH₃CN locates at the fourfold site with the C≡N bonded to four Ni atoms is-1.525eV.On theNi（110） the adsorption energy in the most stable configuration in which CH₃CNlocates at the two long-bridge sites is-1.545eV. All at all,the adsorption energyof the parallel orientation for CH₃CN is larger than that of the perpendicularconfiguration.（2） The adsorption of CH₃NC on the Ni（111）,Ni（100）and Ni（110） surfaceat the1/4monolayer coverage are investigated using the density functiontheory,Due to the special nature of N≡C,it did not appear likely to result inparallel to the surface of the calculation process.But the results show that themost favored adsorption structure for CH₃NC on Ni（111） is h-η3（C）*,and theadsorption energy is-1.990eV.The best adsorption structure for CH₃NC onNi（100）is fourfold（C,N） and the adsorption energy is-2.418eV. On the Ni（110）the adsorption energy in the most stable configuration in which CH₃NC locatesat the two long-bridge sites is-2.394eV.