为探索 SnSe2二维薄膜材料的气敏特性，采用分子力场方法系统地研究了 SnSe2二维单层材料对 H2,CO,NH3及 NO2等 4种典型气体分子的最优吸附位置和吸附能力，并基于密度泛函理论(DFT)的第一性原理方法计算了吸附前后的键长键角变化率、能带结构、态密度及电荷差分密度等参数，分析了吸附前后的电子结构变化与气敏效应之间的内在关联。计算结果发现，吸附 H2和 CO未能对 SnSe2单层的能带结构和电子结构产生改变，而 NO2和 NH3却在导带底 (CBM)和价带顶(VBM)之间分别产生了新的杂质能级，并使费米能级发生位移，从而改变 SnSe2单层电子结构。电荷差分密度分析进一步表明 SnSe2二维单层未能对 H2和 CO产生响应，而对 NH3和 NO2却有明显的气敏效应，其中对 NO2有良好的敏感性能和选择性。

For exploring the gas sensitivity of SnSe2 single atom 2D layer, geometry optimization and energy calculation were carried out to search out the best adsorptive site and sorption capacity for SnSe2 single layer adsorbed respectively with H2, CO, NH3 and NO2 gas molecules. The parameters are calculated based on the first principle method such as Density Functional Theory(DFT) including bond length and its angle, band structure, total density of state, electronic density and charge difference density. The relationship between the electronic structure changes and the gas sensing was studied. The result reveals that H2 and CO cannot change the electronic structure of SnSe2 single layer, but fresh impurity level is generated because of adsorption of NO2 and NH3. This new level locates between Conduction Band Minimum(CBM) and Valence Band Maximum(VBM) and pushes the 509 Fermi level down to VBM by NH3, or up to CBM by NO2 in shallow level. The charge difference density show that nothing changed by H2 and CO adsorbed on SnSe2 single layer, but some electrons gathering occurred locally on sorption site in the layer adsorbed by NO2, and electrons shifted to surface atom after adsorbing NH3. It is distinct that SnSe2 2D single layer has the obvious gas sensitivity for NO2 and NH3 and the good selectivity for NO2 as well.