中文摘要：

近年来,过渡金属硫化物作为催化材料在许多化学反应中扮演着重要角色,特别是在石油化工领域的加氢脱硫与加氢脱氮等环节中被广泛应用.本工作采用密度泛函理论结合高精度的耦合簇[CCSD（T）]计算方法,对掺杂类型的铌钼硫簇NbMoSn-/0（n=37）进行系统研究,确定其最稳定的几何结构,并探讨掺杂、调节硫含量、改变团簇所带电荷等手段,对掺杂类型铌钼硫簇几何构型、电子结构与化学成键等性质的影响.本工作采用广义Koopmans定理计算NbMoSn-（n=3-7）阴离子基态的电子垂直逸出能（VDEs）,模拟相应的阴离子光电子能谱图（PES）,并结合对分子轨道的分析来进一步阐述该体系在几何结构与化学成键等性质上的演变规律.本工作可为进一步开展铌钼硫簇掺杂体系的理论与实验研究提供较为可靠的理论依据.

英文摘要：

Recently, transition metal sulfides（TMS） have played an important role in many catalytic reactions. In particular, they are widely used in the petrochemical industry, such as the hydrodesulfurization（HDS） and the hydrodenitrogenation（HDN） processes. In this work, density functional theory（DFT） and coupled cluster theory [CCSD（T）] calculations were used to study the niobium-mixed di-nuclear molybdenum sulfide clusters NbMoSn-/0（n=3-7）. In our calculations, their ground-state structures were determined and the effects of doping metal, adjusting the sulfur content（n） and changing the charge states of clusters were discussed on the geometries, electronic structures and chemical bonding of NbMoSn-/0（n=3-7）. NbMoSn-/0（n=3-7） clusters can be viewed as linking different sulfur ligands to the NbMoS2 four-membered rings. Among them, diverse poly-sulfur ligands, such as bridging S2, terminal S2 and terminal S3 groups, emerged in the sulfur-rich clusters. Generalized Koopmans＇ Theorem was employed to predict the vertical detachment energies（VDEs）, and simulate the corresponding anionic photoelectron spectra（PES）. The first VDEs（VDE（1st）） of NbMoS-（n=3-6） increased gradually as a function of n, and then decreased suddenly when the sulfur content（n） reached 7. The VDE（1st） reached the maximum by 4.69 eV when the sulfur content equaled to 6. The driving forces（-ΔG） of the reduction reactions between NbMoSn-/0（n=3-7） and H2 were evaluated. The NbMoS7-- anion with the terminal S2-（2-）group yielded the negative value of ΔG, which indicated that the reaction is thermodynamically favored even at the room temperature. We predicted that doping niobium into the molybdenum sulfides may improve the emergence of S2 group which may be helpful in producing the coordinatively unsaturated sites（CUS） under the H2/H2 S atmosphere. Molecular orbital analyses are performed to improve our understanding on the structural evolution and the chemical bonding of NbMoSn-