Wen Xiao-Dong, Zeng Tao, Li Yong-Wang, Wang Jianguo, Jiao Haijun
State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, Shanxi 030001, P. R. China.
J Phys Chem B. 2005 Oct 6;109(39):18491-9. doi: 10.1021/jp051540r.
Density functional theory (DFT) computations have been carried out to study the structure and stability of MoSx clusters with the change of sulfur coverage at both Mo and S edges. DFT shows that adding sulfur to the Mo edge is always exothermic. However, deleting corner sulfur from the S edge is exothermic for 67 and 50% sulfur coverages, while deleting edge sulfur from the S edge is endothermic for 33 and 0% sulfur coverages. On the basis of the computed free energies along a wide range of H2S/H2 ratios, it is found that there are two stable structures with 33 and 50% sulfur coverages on the Mo edge by having 100% sulfur coverage on the S edge and one stable structure with 67% sulfur coverage on the S edge by having 0% sulfur coverage on the Mo edge. Under fully sulfiding atmosphere or at a very high H2S/H2 ratio, triangle MoSx structures with 100% sulfur coverage on the Mo edge are computed to be more stable than those with 100% sulfur coverage on the S edge, in agreement with the observation of scanning tunneling microscopy. In addition, the effects of cluster sizes on the surface structures are discussed.
已进行密度泛函理论（DFT）计算，以研究MoSx团簇在Mo和S边缘硫覆盖率变化时的结构和稳定性。DFT表明，在Mo边缘添加硫总是放热的。然而，从S边缘去除角部硫对于67%和50%的硫覆盖率是放热的，而从S边缘去除边缘硫对于33%和0%的硫覆盖率是吸热的。基于在广泛的H2S/H2比率范围内计算出的自由能，发现在S边缘具有100%硫覆盖率时，Mo边缘存在两种具有33%和50%硫覆盖率的稳定结构，以及在Mo边缘具有0%硫覆盖率时，S边缘存在一种具有67%硫覆盖率的稳定结构。在完全硫化气氛或非常高的H2S/H2比率下，计算得出Mo边缘具有100%硫覆盖率的三角形MoSx结构比S边缘具有100%硫覆盖率的结构更稳定，这与扫描隧道显微镜的观察结果一致。此外，还讨论了团簇尺寸对表面结构的影响。
