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采用色散校正密度泛函方法(DFT-D2)研究了Fe同晶取代进入丝光沸石骨架中的可能位置及其对NH3分子的吸附。结果表明,Fe优先取代位是T1O6位,然后依次是T2O5,T4O2和T3O1位,且能量差小于0.09 eV,说明Fe可能分布在四种非等价晶体T位,而且电荷平衡质子的位置影响Fe取代位的稳定性。本文还采用DFT和DFT-D2方法计算了NH3分子在每一个Fe取代的T位的吸附能。通过比较发现,DFT低估了NH3的吸附能约0.53 eV,这表明DFT-D2方法对于NH3吸附是很有必要的,且结果与文献相符,T2O5位的Brnsted酸性最强,NH3在Brnsted酸位的吸附比在Lewis酸位的吸附更稳定。
The possible location of the substitution of Fe into the mordenite framework and its adsorption of NH3 molecules were investigated by the dispersion-corrected density functional theory (DFT-D2). The results show that the preferred substitution sites for Fe are T1O6, followed by T2O5, T4O2 and T3O1, and the energy difference is less than 0.09 eV, indicating that Fe may be distributed in the T sites of the four non-equivalent crystals and that the position of the charge-balancing protons affects Fe Substitute for the stability of the bits. We also use the DFT and DFT-D2 methods to calculate the adsorption energy of the NH3 molecule at each T-substituted Fe site. It was found by comparison that DFT underestimated the adsorption energy of NH3 by about 0.53 eV, indicating that the DFT-D2 method is necessary for the NH3 adsorption. The results are consistent with the literature. Bromnsted acidity is the strongest at T2O5, The adsorption of nsted acid sites is more stable than that of Lewis acid sites.