Theoretical Investigation On The Adsorption Mechanism Of Acrylonitrile And 1,3-Cyclohexadiene On The Diamond (001)-2×1 Reconstruction Surface

The fascinating and unique combination of mechanical, electrical, thermal and optical properties of diamond makes it being one of the most promising candidates for a wide variety of applications. The chemical functionalization of the diamond surface can introduce new physical and chemical properties, thus leading to the improvement of its behavior for specific applications. Organic and biological functionalization of diamond surface represents an important topic in recent years. In this paper, the adsorption mechanism of two kinds of molecules on diamond (001) surface has been studied theoretically.Firstly, the reaction of acrylonitrile with the C (001)-2×1 reconstruction surface has been investigated by means of density functional cluster model calculations. The investigation indicates that the adsorption process is very complex. Eight unique reaction channels involving two surface dimers along and across the dimer-rows were identified. Full geometry optimized structures were obtained for all adducts, including intra- and inter- dimer reaction products. These results were analyzed both in terms of the total energy values and the detailed optimized geometries. We find that the reaction of acrylonittrile with the diamond (001) surface occurs primarily through its nonpolar C=C group and the intradimer [2+2]cc product is the dominant product. All these results are in good agreement with the experimental work by Michael P. Schwartz. It is noteworthy that the isomerization process plays an important role in the chemisorption process. Both intradimer [4+2] product and interdimer [2+2]cc product can isomerize to the intradimer [2+2]cc product.Secondly, by means of density functional theory coupled with effective cluster models, we theoretically studied the [4+2] and [2+2] cycloaddition reactions between 1,3-cyclohexadiene and diamond (001)-2×1 surface. The calculations revealed four possible reaction pathways for 1,3-cyclohexadiene with the surface dimers. Full geometry optimized structures were obtained for all adducts, including intra- and interdimer reaction products. These results were analyzed both in terms of the total energy values and the detailed optimized geometries. We find that the intradimer [4+2] product is energetically favored over the other products, and the barrier to intradimer [4+2] addition is lower than the other additions, so the intradimer [4+2] product is expected to be the dominant product on the surface.