Periodic modeling of zeolite Ti-LTA.
Periodic modeling of zeolite Ti-LTA.
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DOI：
10.1063/1.4998296
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发表时间：
2017-08
期刊：
影响因子：
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通讯作者：
Carlos E. Hernandez-Tamargo;A. Roldan;P. Ngoepe;N. D. de Leeuw
中科院分区：
文献类型：
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作者：
Carlos E. Hernandez-Tamargo;A. Roldan;P. Ngoepe;N. D. de Leeuw
我们提出了一个密度泛函理论计算和基于原子间势的模拟相结合，研究结构，电子和机械性能的纯硅沸石林德A型（LTA），以及两个钛掺杂的组合物。沸石骨架内钛分布的能量学表明，包含具有构型Ti-（Si）0-Ti、Ti-（Si）1-Ti和Ti-（Si）2-Ti的第二钛原子比单取代在能量上更有利。模拟了纯二氧化硅LTA、单钛取代以及Ti-（Si）0-Ti和Ti-（Si）2-Ti构型的红光光谱，并与实验基准进行了比较。水在这些刘易斯酸中心上的直接解离的能量学表明，只有当两个钛原子形成共享两个羟基的二元环（2 MR）Ti-（OH）2-Ti时，该过程才有利，这表明水的存在可以调节钛原子在沸石LTA骨架内的分布。电子结构分析表明，H_2O与刘易斯酸中心发生了电荷转移，电子态发生了杂化。
We have proposed a combination of density functional theory calculations and interatomic potential-based simulations to study the structural, electronic, and mechanical properties of pure-silica zeolite Linde Type A (LTA), as well as two titanium-doped compositions. The energetics of the titanium distribution within the zeolite framework suggest that the inclusion of a second titanium atom with configurations Ti-(Si)0-Ti, Ti-(Si)1-Ti, and Ti-(Si)2-Ti is more energetically favorable than the mono-substitution. Infra-red spectra have been simulated for the pure-silica LTA, the single titanium substitution, and the configurations Ti-(Si)0-Ti and Ti-(Si)2-Ti, comparing against experimental benchmarks where available. The energetics of the direct dissociation of water on these Lewis acid sites indicate that this process is only favored when two titanium atoms form a two-membered ring (2MR) sharing two hydroxy groups, Ti-(OH)2-Ti, which suggests that the presence of water may tune the distribution of titanium atoms within the framework of zeolite LTA. The electronic analysis indicates charge transfer from H2O to the Lewis acid site and hybridization of their electronic states.