金红石TiO_2纳米团簇与铀酰相互作用的相对论密度泛函理论计算
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摘要
采用全电子相对论密度泛函理论方法探索金红石型Ti O_2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-[(UO_2)(H_2O)_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-O_(surf)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 e V);考虑溶剂介质环境的影响,反应则需要吸收少许能量(0.16e V)。U-O_(surf)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-O_(surf)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-OH_2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 e V,相对吸附前的纳米团簇半导体粒子的3.35 e V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。
The interaction between rutile Ti O_2nanoparticle 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 Ti O_2nanocrystallite.Moreover,the model is able to save computational resources.Calculations reveal a covalent bonding interaction in the 2L-Ti15-[(UO_2)(H_2O)_3]~(2+)complex.The direct evidences include that the bond lengths of U-O_(surf)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 e V;the consideration of environment media of solution results in a slightly uphill process,requiring 0.16 e V energy.The energetic decomposition indicates that U-O_(surf)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-O_(surf)interaction is a dative bond per se,whose strength is stronger than that of U-OH_2,but much weaker than that of U=O_(yl).Inspection of wavefunction demonstrates that HOMO is contributed by O(2p)of NPC Ti O_2mixed with a small amount ofσ(U=O)bonding character,while LUMO is U(5f)-based character modified by Ti(3d).The HOMO-LUMO gap was calculated to be2.40 e V,which much narrower than the one of NPC semiconductor(3.35 e V).From a point of view of absorption spectra,the complex system would present a visible light-harvesting capability.
The interaction between rutile Ti O_2nanoparticle 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 Ti O_2nanocrystallite.Moreover,the model is able to save computational resources.Calculations reveal a covalent bonding interaction in the 2L-Ti15-[(UO_2)(H_2O)_3]~(2+)complex.The direct evidences include that the bond lengths of U-O_(surf)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 e V;the consideration of environment media of solution results in a slightly uphill process,requiring 0.16 e V energy.The energetic decomposition indicates that U-O_(surf)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-O_(surf)interaction is a dative bond per se,whose strength is stronger than that of U-OH_2,but much weaker than that of U=O_(yl).Inspection of wavefunction demonstrates that HOMO is contributed by O(2p)of NPC Ti O_2mixed with a small amount ofσ(U=O)bonding character,while LUMO is U(5f)-based character modified by Ti(3d).The HOMO-LUMO gap was calculated to be2.40 e V,which much narrower than the one of NPC semiconductor(3.35 e V).From a point of view of absorption spectra,the complex system would present a visible light-harvesting capability.
引文
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[3]GU Jia-Fang(辜家芳),XU Ke(许可),CHEN Wen-Kai(陈文凯).Chinese J.Inorg.Chem.(无机化学学报),2017,33(9):1579-1586
[4]Natrajan L S,Swinburne A N,Andrews M B,et al.Coord.Chem.Rev.,2014,266:171-193
[5]Sandhu S S,Kohli K B,Brar A S.Inorg.Chem.,1984,23(22):3609-3612
[6]Nieweg J A,Lemma K,Trewyn B G,et al.Inorg.Chem.,2005,44(16):5641-5648
[7]Krishna V,Kamble V S,Gupta N M,et al.J.Phys.Chem.C,2008,112(40):15832-15843
[8]Vandenborre J,Drot R,Simoni E.Inorg.Chem.,2007,46(4):1291-1296
[9]Zhao S,Zhong Y,Guo Y,et al.Acta Chim.Sinica,2016,74(8):683-688
[10]GU Jia-Fang(辜家芳),MAN Mei-Ling(满梅玲),LU ChunHai(陆春海),et al.Chinese.J.Inorg.Chem.(无机化学学报),2012,28(7):1324-1332
[11]Perron H,Domain C,Roques J,et al.Inorg.Chem.,2006,45(17):6568-6570
[12]Pan Q J,Odoh S O,Schreckenbach G,et al.Dalton Trans.,2012,41(29):8878-8885
[13]Zhao H B,Zheng M,Schreckenbach G,et al.Inorg.Chem.,2017,56(5):2763-2776
[14]Dossot M,Cremel S,Vandenborre J,et al.Langmuir,2006,22(1):140-147
[15]Laikov D N.Chem.Phys.Lett.,1997,281(1/2/3):151-156
[16]Fonseca Guerra C,Snijders J G,te Velde G,et al.Theor.Chem.Acc.,1998,99(6):391-403
[17]Bader R F W.J.Phys.Chem.A,1998,102:7314-7323
[18]Pye C C,Ziegler T.Theor.Chem.Acc.,1999,101(6):396-408
[19]van Lenthe E,Baerends E J,Snijders J G.J.Chem.Phys.,1993,99(6):4597-4610
[20]Frisch M J,Trucks G W,Schlegel H B,et al.Gaussian09,Gaussian,Inc.,Wallingford CT,2009.
[21]Lu T,Chen F.J.Comput.Chem.,2012,33(5):580-592
[22]Pan Q J,Schreckenbach G.Inorg.Chem.,2010,49(14):6509-6517
[23]Arnold P L,Jones G M,Odoh S O,et al.Nat.Chem.,2012,4(3):221-227
[24]Den Auwer C,Drot R,Simoni E,et al.New J.Chem.,2003,27(3):648-655
[25]Sebbari K,Roques J,Simoni E,et al.Surf.Sci.,2012,606(15/16):1135-1141