First-principle Study On W₁₈O₄₉ Nanowire And Its Adsorption Property Of NO₂

This paper based on first-principles density functional study of the adsorption ofNO2affect on W18O49nanowires electrical properties, including band structure,density of states and electron population. Compared with previous calculation, bulkW18O49have an asymmetric structure, so we constructed two nanowire models, whichinclude W5+ions and W6+ions separately so that the different W18O49atoms arecontained in the nanowires. By calculating the energy of two kinds of nanowiresvarious adsorption models and choosing the lowest energy model as the optimal one,then discuss its adsorption properties. Adsorption of NO2will introduce new energy inthe valence band and makes the Fermi level moves toward the gap and then decreasethe charge carrier concentration. By comparing the Atomic Mulliken populationbetween W18O49and WO3nanowires, the adsorption of NO2on W18O49nanowiresurface can lead to more electron transfer to NO2, show W18O49nanowires havehigher NO2gas adsorption properties. This conclusion is consistent with theexperimental results.Compared with W5+\6+, Ti4+ions has lower valence states, so Ti doped nanowireswill have more defects and structure distortion. The influences of doping to two kindsof nanowires’ energy were the same and both reduced the stability of nanowires, thenanowires’electron wave function were crossed. These influences were greater on theband structure near Fermi level. After calculated the adsorption energy of dopednanowire, we can find that the nanowires can instead of higher adsorption energy,which means that the nanowires become more unstable. For different nanowires dueto the different atomic composition and structure, the electronic structure is alsodifferent. Namely, in the material, different parts of the material composed nanowireshave different doping structure and adsorption properties which show differentgas-sensing properties. By analyzing the Atomic Mulliken population of those twokinds doped nanowire models N-O6and N-O11,we can find that NO2act as electronicreceiver and capture1.13e and1.22e respectively from two kinds doped nanowiremodels, the captured electron number were greater than pure nanowires adsorption(1.06e and1.12e). Quantitatively reflects the Ti doping can improve the W18O49nanowire’gas sensitive property.