金红石TiO2纳米团簇与铀酰相互作用的相对论密度泛函理论计算
Relativistic DFT Calculations of Interaction between Rutile TiO2 Nanoparticle Clusters and Uranyl Species
作者单位E-mail
郑明 黑龙江大学功能无机材料化学教育部重点实验室, 化学化工与材料学院, 哈尔滨 150080  
张红星 吉林大学理论化学研究所, 长春 130023  
袁福龙 黑龙江大学功能无机材料化学教育部重点实验室, 化学化工与材料学院, 哈尔滨 150080 panqjitc@163.com 
潘清江 黑龙江大学功能无机材料化学教育部重点实验室, 化学化工与材料学院, 哈尔滨 150080 yuanfulong@hlju.edu.cn 
摘要: 采用全电子相对论密度泛函理论方法探索金红石型TiO2纳米团簇与铀酰的相互作用。考察金红石团簇模型(包括层数和表面积大小)变化对吸附铀形成复合物结构、吸附作用能等性质的影响,确定2层、表面积为1.1 nm×0.6 nm、包括63个原子的纳米团簇(标记为2L-Ti15)能够合理描述金红石纳米粒子性质的同时,还能节约计算资源。对2L-Ti15-[(UO2)(H2O)3]2+复合物计算表明,纳米团簇和铀酰存在共价键作用;优化得到U-Osurf键长0.233~0.238 nm,这一距离在已发现铀酰基配合物U-O距离范围内。在气相条件下,纳米团簇对铀酰吸附反应为放热过程(-3.02 eV);考虑溶剂介质环境的影响,反应则需要吸收少许能量(0.16 eV)。U-Osurf键的能量分解发现,纳米团簇和铀酰的化学键作用为轨道相互作用主导的(占94%),它的静电吸引略大于Pauli排斥。基于电子密度的QTAIM(quantum theory of atoms in molecule)分析揭示,U-Osurf作用是介于离子和共价之间的配位键,其强度高于复合物中的U-OH2键作用,但比U=O键弱。波函数分析表明,来自纳米团簇的O(2p)贡献HOMO轨道,并混有σ(U=O)成键性质,而LUMO轨道则为Ti(3d)修饰的U(5f)性质,复合物HOMO-LUMO带隙为2.40 eV,相对吸附前的纳米团簇半导体粒子的3.35 eV变窄。从吸收光谱角度而言,复合物体系可能在可见光区域具有更强的捕光性能。
关键词: 金红石TiO2纳米团簇  铀污染物  吸附作用本质  电子结构  相对论密度泛函理论
基金项目: 国家自然科学基金(No.21671060,21273063)资助项目。
Abstract: The interaction between rutile TiO2 nanoparticle clusters (NPCs) and aquouranyl species have been examined using a relativistic functional theory (DFT). Effects of NPCs with various layers (1~4) and different surface areas on structural parameters of uranium adsorption complexes as well as adsorption interaction energies were investigated. It is found that the two-layered (2L) NPC (labeled as 2L-Ti15) with a surface area of 1.1 nm×0.6 nm and containing 63 atoms can reasonably stand for experimentally real TiO2 nanocrystallite. Moreover, the model is able to save computational resources. Calculations reveal a covalent bonding interaction in the 2L-Ti15-[(UO2)(H2O)3]2+ complex. The direct evidences include that the bond lengths of U-Osurf were optimized to be 0.233~0.238 nm, which fall well within the range of U-O distances of reported uranyl complexes. The process that the NPC adsorbs aquouranyl species is exothermic in the gas phase, releasing energy of -3.02 eV; the consideration of environment media of solution results in a slightly uphill process, requiring 0.16 eV energy. The energetic decomposition indicates that U-Osurf bonds are dominated by orbital interactions, accounting for 94%; other factors show a little effect, although electrostatic attraction is a little larger than Pauli repulsion. Electron density-based QTAIM (quantum theory of atoms in molecule) analyses unravel that the U-Osurf interaction is a dative bond per se, whose strength is stronger than that of U-OH2, but much weaker than that of U=Oyl. Inspection of wavefunction demonstrates that HOMO is contributed by O(2p) of NPC TiO2 mixed with a small amount of σ(U=O) bonding character, while LUMO is U(5f)-based character modified by Ti(3d). The HOMO-LUMO gap was calculated to be 2.40 eV, which much narrower than the one of NPC semiconductor (3.35 eV). From a point of view of absorption spectra, the complex system would present a visible light-harvesting capability.
Keywords: rutile TiO2 nanoparticle clusters  uranium contaminant  adsorption interaction nature  electronic structures  relativistic DFT
投稿时间:2017-10-28 修订日期:2018-02-07
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郑明,张红星,袁福龙,潘清江.金红石TiO2纳米团簇与铀酰相互作用的相对论密度泛函理论计算[J].无机化学学报,2018,34(5):874-882.
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