Feasibility of Benzene Dissociation on the Singlet and Triplet Electronic States of Selected Cluster Models for the Si(100) Surface

作者：Zhu Qing; Materer Nicholas F^*

来源：Journal of Physical Chemistry C, 2011, 115(27): 13377-13385.

DOI：10.1021/jp203325q

Density functional theory was used to investigate possible adsorption and dissociation processes for benzene on the Si(100) surface using Si-dimer clusters. On this surface, benzene can react across a Si-dimer in a 1,2 manner across a double bond or in a 1,4 route across the benzene molecule to form a di-sigma chemisorbed product. At this level, the transition state geometry from the gas phase into either of these di-sigma products is activated and suggests a diradial adsorption mechanism. The activation energy to form the 1,4 bond product (a butterfly configuration) is significantly less than other possible chemisorbed products. After adsorption, the 1,2 bond product (a tilted configuration) can undergo C H bond cleavage to form lower-energy products. However, a previously reported one-step C H cleavage pathway to form a doubly dissociative product is not possible,and more complex processes involving spin-crossing must be considered. After a spin-crossing process, a triplet 1,2 bond product can follow two possible dissociative pathways. One reaction pathway forms a product consisting of an absorbed phenyl group and hydrogen. The other product requires two C H bonds to break and two H Si bonds to form and is absorbed to the surface via two C Si bonds. Both processes require a spin-crossing of the initial 1,2 bond product and a transition state with large activation barriers with respect to desorption or further reactions of remaining double bonds with an adjacent Si-dimer (a titled-bridge structure). Thus, these dissociation pathways are unlikely to occur under typical experimental conditions.

• 出版日期2011-7-14