Fig. 1. (a) Schematic diagram of four different adsorption sites; the top view and side view of the most favorable configurations of monolayer WTe₂ with (b) CO, (c) CO₂, (d) NH₃, (e) NO, and (f) NO₂ adsorption; the definition of adsorption distance d is shown in (b). (a) 四个不同的吸附位点示意图; (b) CO, (c) CO₂, (d) NH₃, (e) NO和(f) NO₂吸附在单层WTe₂表面最稳定构型的俯视图和侧视图; 吸附距离d的定义如 (b) 所示

Fig. 2. Adsorption distance and adsorption energy for CO, CO₂, NH₃, NO, and NO₂ on WTe₂ monolayer. CO, CO₂, NH₃, NO, NO₂气体分子与单层WTe₂之间的吸附距离和吸附能

Fig. 3. The charge difference between WTe₂ monolayer and gas molecules for (a) CO, (b) CO₂, (c) NH₃, (d) NO and (e) NO₂. The isosurface is taken as 6.0 × 10^–4e/ų. The electron accumulation (depletion) is indicated by yellow (blue) color. The direction (indicated by an arrow) and value of the charge transfer are shown. (a) CO, (b) CO₂, (c) NH₃, (d) NO和 (e) NO₂气体分子与单层WTe₂之间的差分电荷密度. 等值面取6.0 × 10^–4e/ų, 电子积累(损耗)分别用黄色(蓝色)表示, 同时标注了电荷转移的方向(用箭头表示)和电荷转移量

Fig. 4. (a) The band structure of pristine WTe₂; band structure of (b) CO, (c) CO₂ and (d) NH₃ adsorbed on WTe₂ monolayer; band structure of (e), (f) NO and (g), (h) NO₂ adsorbed on WTe₂ monolayer, the blue and red lines represent the band structure of spin-up and spin-down, respectively. The olive dots represent the projected band structure of the adsorbed gas molecules. (a) 本征WTe₂的能带结构图; (b) CO, (c) CO₂和 (d) NH₃吸附在单层WTe₂表面的能带结构图; (e), (f) NO和 (g), (h) NO₂吸附在单层WTe₂表面的能带结构图. 其中蓝线和红线分别表示自旋向上和自旋向下的能带结构, 橄榄色的点线表示吸附气体分子的投影能带结构

Fig. 5. The density state of (a) CO, (b) CO₂, (c) NH₃, (d) NO and (e) NO₂ adsorbed on WTe₂ monolayer, respectively. The spin density distribution of (f) NO and (g) NO₂ adsorbed on WTe₂ monolayer (a) CO, (b) CO₂, (c) NH₃, (d) NO和 (e) NO₂分别吸附在单层WTe₂上的分态密度图; (f) NO和 (g) NO₂吸附在WTe₂表面的自旋密度分布图