中文摘要：

采用基于密度泛函理论框架下的第一性原理平面波超软赝势方法，通过理论建模，研究了Ti掺杂的非化学计量比W18O49纳米线的几何与能带结构以及电子态密度，并通过进一步计算NO2／Ti-W18O49纳米线吸附体系的吸附能、电荷差分密度与电荷布居，分析了Ti掺杂W18O49纳米线的气体吸附与敏感性能．计算发现，Ti掺杂改变了W18O49纳米线的表面电子结构，引入的额外的杂质态密度和费米能级附近能带结构的显著变化，使掺杂纳米线带隙与费米能级位置改变，纳米线导电性能增强．吸附在W18O49纳米线表面的N02作为电子受体从纳米线导带夺取电子，导致纳米线电导降低，产生气体敏感响应．与纯相W18O49纳米线相比，NO2／Ti-W18O49纳米线吸附体系内部存在更多的电子转移，从理论上定量地反映了Ti掺杂对改善W18O49纳米线气敏灵敏度的有效性．对Ti掺杂纳米线不同气体吸附体系电子布居的进一步计算表明，Ti掺杂纳米线对NO2气体具有良好的灵敏度和选择性．

英文摘要：

The geometry and band structures as well as the density of states of Ti-doped nonstoichiometric WlsO49 nanowire are studied by employing the ab- initio plane-wave ultra-soft pseudo potential technique based on the density functional theory. Meanwhile, the adsorption and NO2-sensing properties of the doped nanowire are analyzed by further calculating the adsorption energy, planar averaged charge density difference and atomic Mulliken charge population of the NO2/Ti W18O49 nanowire adsorption system. The results reveal that Ti-doping modifies the electronic structure and then the gas sensitivity of W18O49 nanowire obviously. After Ti-doping, new electronic states are introduced and the band structure near Fermi level （EF） is changed obviously, resulting in the variation of the band gap and EF position and then the increase of electronic conductivity. The adsorbed NO2 molecule acts as a charge accepter to extract electrons from the conduction band of W18O49 nanowire, causing the gas-sensing response due to the conductivity change of the nanowire. NO2 adsorptioa on Tl-doped W18O49 nanowire can cause more electrons to transfer from nanowire to NO2 molecule than the case on pure W18O49 nanowire, theoretically suggesting the validity of Ti-doping that can improve the sensitivity of W18O49 nanowire. The population cMculations on different gas molecules adsorbed on Ti-doped W18O49 nanowire further indicate the much good sensitivity and selectivity of the doped nanowire to NO2 gas.