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采用两种大小不同的原子簇模型Si3 0 H2 8和Si13 H16,分别用两层ONIOM方法 (对较大原子簇 )和普通量子化学方法 (对较小原子簇 )考察了苯分子在Si(111) 7× 7表面的化学吸附 .对三种可能的吸附物种分别用DFT或HF方法进行了计算 .通过大小原子簇吸附物种的吸附能以及几何构型优化参数的比较发现 ,对于稳定的吸附物种 ,较小的原子簇基本上可以代替较大的原子簇进行计算 ,而对于不太稳定的吸附物种 ,就不得不考虑周边原子的影响 .计算结果表明苯在Si(111) 7× 7表面的主要吸附物种是双σ成键的 1,4加成产物 ,不稳定的单吸附物种可能是 1,4加成物种的前驱态 .
Two kinds of atomic cluster models Si3 0 H2 8 and Si13 H16 with different sizes were used to study the effect of benzene molecules on the Si (111) clusters by using two layers of ONIOM method (for larger clusters) and ordinary quantum chemistry (for smaller clusters) ) 7 × 7 surface chemisorption.The three possible adsorbed species were calculated by DFT or HF method respectively.The comparison of the adsorption energies and geometrical configuration parameters of the adsorbed species of the size cluster showed that for the stable adsorbed species , Smaller clusters can basically be calculated instead of larger clusters, and for the less stable species, we have to consider the influence of the surrounding atoms. The calculated results show that benzene on Si (111) 7 × 7 surface The major adsorbate species are 1,4-addition products with double σ bonds, and the unstable single-adsorbed species may be the precursor for 1,4-addition species.