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...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。展开更多
使用密度泛函理论(B3LYP)方法,结合准相对论有效核势(ECP)和二分量ZORA相对论Hamiltonian,探索三明治型四聚吡咯铀配合物LUmL'(配体为porphyrizine或porphyrine;m=III和IV)的结构、成键和反应性质。优化多种空间和"电子自旋态&...使用密度泛函理论(B3LYP)方法,结合准相对论有效核势(ECP)和二分量ZORA相对论Hamiltonian,探索三明治型四聚吡咯铀配合物LUmL'(配体为porphyrizine或porphyrine;m=III和IV)的结构、成键和反应性质。优化多种空间和"电子自旋态"异构体结构,发现铀配合物具有交叉式、高电子自旋态的基态。QTAIM(Quantum theory of atoms in molecule)的U-N键临界点处的电子/能量密度拓扑分析以及counterpoise计算U-N作用能,揭示该化学键为弱极性共价键。计算显示在采用适当的三价和四价铀源和强碱性配体时,可经过放热反应生成配合物。考虑溶剂(苯、THF和水)和旋-轨耦合影响,计算从四价铀配合物到三价的还原电势,得到数值均小于1 V,这与四价配合物相对稳定、三价铀配合物具有强还原性的实验结果相符合。研究发现降低溶剂极性,配合物的还原电势向负方向移动,这可为实验中采用溶剂极性来调控配合物的氧化还原性质提供理论指导。展开更多
为探索四聚吡咯配体和低价铀离子相互作用,以实验合成单层三明治结构配合物PcU~ⅥPc(Pc=酞菁)为基础,设计双层三明治型PzU^mPzU^mPz(m=Ⅲ,Ⅳ,Pz=氮杂卟啉),采用相对论密度泛函理论考察了其几何结构、异构体相对稳定性以及成键和轨道性质...为探索四聚吡咯配体和低价铀离子相互作用,以实验合成单层三明治结构配合物PcU~ⅥPc(Pc=酞菁)为基础,设计双层三明治型PzU^mPzU^mPz(m=Ⅲ,Ⅳ,Pz=氮杂卟啉),采用相对论密度泛函理论考察了其几何结构、异构体相对稳定性以及成键和轨道性质.得到se(staggered-eclipsed)和es(eclipsed-staggered)2种类型稳定空间异构体,并进一步优化其所有可能的电子自旋态异构体.计算结果表明,这些低价铀配合物均具有五重态基态.分子中的原子量子理论(quantum theory of atoms in molecule,QTAIM)在U—N键临界点处的电子/能量密度拓扑分析显示U—N键为弱极性共价键.四价配合物拥有4个U(5f)性质高能占据轨道,与2个U4+的5f单电子数相一致;而三价配合物有很大配体参与作用.2个铀原子和中间Pz配体质心近似成线性,这与配合物具有稳定的σ(U—U)成键轨道密切相关.展开更多
采用全电子相对论密度泛函理论探索多种六聚吡咯大环锕酰基配合物(nAn;n=1~3;An=U,Np and Pu)的电子结构本质、成键规律和化学反应特性。结构优化发现大环配体空穴大小与锕酰离子尺寸相当时,配合物锕酰基采用性对规则的六角双锥结构,而...采用全电子相对论密度泛函理论探索多种六聚吡咯大环锕酰基配合物(nAn;n=1~3;An=U,Np and Pu)的电子结构本质、成键规律和化学反应特性。结构优化发现大环配体空穴大小与锕酰离子尺寸相当时,配合物锕酰基采用性对规则的六角双锥结构,而当空穴尺寸相对大时,配合物则采取扭曲结构以降低体系能量。当配体相同时,随着铀、镎、钚变化,An=O伸缩振动频率逐渐变小,这与优化的键长和键级变化规律相一致。QTAIM(quantum theory of atoms in molecule)拓扑分析显示An-N为弱共价单键特征,具有较大离子性成分。依据不同铀源,得到与大环配体的反应自由能均小于146 kJ·mol^(-1),与实验合成配合物的反应能计算数值相当。对含铀配合物电子吸收光谱计算显示,低能(近红外和可见光区)的吸收带具有全部或较大的配体→金属电荷转移性质贡献。展开更多
Low-lying electronic states of the lutetium dimer （Lu2） were studied based on density functional theory （DFT） using ten different density functionals together with three different relativistic effective core pseud...Low-lying electronic states of the lutetium dimer （Lu2） were studied based on density functional theory （DFT） using ten different density functionals together with three different relativistic effective core pseudopotentials （RECPs）. Relative state energies, equilibrium bond lengths, vibrational frequencies, and ground-state dissociation energies were evaluated. It was found that the ground state is a triplet state irrespective of the type of functional and RECP used. This result is in contrast with a previous DFT calculation which gave a singlet ground state for Lu2. By comparing with the high-level ab initio and available experimental results, it is evident that the hybrid-GGA functionals combined with the Stuttgart smallcore RECP yield the best overall agreement for the properties under study. The effects of Hartree-Fock exchange in B3LYP functional on the calculated bond length and dissociation energy of the ground state were examined, and rationalized in terms of 5d participation in Lu-Lu covalent bonding.展开更多
经三十余年努力,二价铀溶液化学于近年取得突破性进展,Evans和Meyer等成功获得两个可通过X-ray晶体衍射表征结构的有机金属铀(Ⅱ)配合物.为进一步拓展U~Ⅱ配合物化学和探索可能存在的金属多重键,设计双核配合物[(U~Ⅱ)_2(L)](L为八齿氮...经三十余年努力,二价铀溶液化学于近年取得突破性进展,Evans和Meyer等成功获得两个可通过X-ray晶体衍射表征结构的有机金属铀(Ⅱ)配合物.为进一步拓展U~Ⅱ配合物化学和探索可能存在的金属多重键,设计双核配合物[(U~Ⅱ)_2(L)](L为八齿氮供体低聚吡咯大环四价阴离子),并使用相对论密度泛函理论优化其可能的电子自旋态异构体结构和计算相关性质.结果表明,[(U~Ⅱ)_2(L)]具有三重态基态,其电子组态为π~4σ~2δ~2;U(5f)原子轨道对高占据分子轨道有重要贡献;它的U—U键长为2.33?、Mayer键级为3.89和对应的伸缩振动频率为259 cm^(–1),被指认为U—U弱四重键.这一结论与QTAIM(quantum theory of atoms in molecule)的U—U键临界点处的电子/能量密度拓扑分析结果相一致.与不同氧化态铀同类物[(U^m)_2(L)]^(n+)(m=ⅡI,n=2;m=IV,n=4)比较显示,随着铀氧化态增大,U—U距离增长、键级变小、伸缩振动频率变小,金属铀电子自旋密度与常规预期值的差值(?SU)增大;结合分子轨道和QTAIM参数分析,发现金属氧化态可以调控配体和金属轨道能级匹配程度和改变金属-金属多重键.展开更多
Since the discovery of the halo nucleus ^(11)Li in 1985,halo phenomena in exotic nuclei have always been an important frontier in nuclear physics research.The relativistic density functional theory has achieved great ...Since the discovery of the halo nucleus ^(11)Li in 1985,halo phenomena in exotic nuclei have always been an important frontier in nuclear physics research.The relativistic density functional theory has achieved great success inthestudyofhalonucleg,theself-consistent description ofhalonucleusLiandthe microscopic predic tion of deformed halo nuclei.This paper introduces some recent progresses based on the deformed relativistic Hartree-Bogoliubov theory in continuum(DRHBc)and the triaxial relativistic Hartree-Bogoliubov theory in continum(TRHBc).A microscopic and self-consistent description of the deformed halo nucleus ^(37)Mg,including its small one-neutron separation energy,large root-mean-square radius,diffuse density distribution,and p-wave components for the halo neutron,has been achieved by the DRHBc theory.The DRHBc theory has also predicted a deformed neutron halo and the collapse of the N=28 shll closureintherecently discovered isotope ^(39)Na The TRHBc theory has been newly developed and applied to the aluminum isotopic chain.The heaviest odd-odd ^(42)AI has been predicted as a triaxial halo nucleus with a novel shape decoupling between its core and halo at the triaxial level.展开更多
文摘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。
文摘使用密度泛函理论(B3LYP)方法,结合准相对论有效核势(ECP)和二分量ZORA相对论Hamiltonian,探索三明治型四聚吡咯铀配合物LUmL'(配体为porphyrizine或porphyrine;m=III和IV)的结构、成键和反应性质。优化多种空间和"电子自旋态"异构体结构,发现铀配合物具有交叉式、高电子自旋态的基态。QTAIM(Quantum theory of atoms in molecule)的U-N键临界点处的电子/能量密度拓扑分析以及counterpoise计算U-N作用能,揭示该化学键为弱极性共价键。计算显示在采用适当的三价和四价铀源和强碱性配体时,可经过放热反应生成配合物。考虑溶剂(苯、THF和水)和旋-轨耦合影响,计算从四价铀配合物到三价的还原电势,得到数值均小于1 V,这与四价配合物相对稳定、三价铀配合物具有强还原性的实验结果相符合。研究发现降低溶剂极性,配合物的还原电势向负方向移动,这可为实验中采用溶剂极性来调控配合物的氧化还原性质提供理论指导。
文摘为探索四聚吡咯配体和低价铀离子相互作用,以实验合成单层三明治结构配合物PcU~ⅥPc(Pc=酞菁)为基础,设计双层三明治型PzU^mPzU^mPz(m=Ⅲ,Ⅳ,Pz=氮杂卟啉),采用相对论密度泛函理论考察了其几何结构、异构体相对稳定性以及成键和轨道性质.得到se(staggered-eclipsed)和es(eclipsed-staggered)2种类型稳定空间异构体,并进一步优化其所有可能的电子自旋态异构体.计算结果表明,这些低价铀配合物均具有五重态基态.分子中的原子量子理论(quantum theory of atoms in molecule,QTAIM)在U—N键临界点处的电子/能量密度拓扑分析显示U—N键为弱极性共价键.四价配合物拥有4个U(5f)性质高能占据轨道,与2个U4+的5f单电子数相一致;而三价配合物有很大配体参与作用.2个铀原子和中间Pz配体质心近似成线性,这与配合物具有稳定的σ(U—U)成键轨道密切相关.
文摘采用全电子相对论密度泛函理论探索多种六聚吡咯大环锕酰基配合物(nAn;n=1~3;An=U,Np and Pu)的电子结构本质、成键规律和化学反应特性。结构优化发现大环配体空穴大小与锕酰离子尺寸相当时,配合物锕酰基采用性对规则的六角双锥结构,而当空穴尺寸相对大时,配合物则采取扭曲结构以降低体系能量。当配体相同时,随着铀、镎、钚变化,An=O伸缩振动频率逐渐变小,这与优化的键长和键级变化规律相一致。QTAIM(quantum theory of atoms in molecule)拓扑分析显示An-N为弱共价单键特征,具有较大离子性成分。依据不同铀源,得到与大环配体的反应自由能均小于146 kJ·mol^(-1),与实验合成配合物的反应能计算数值相当。对含铀配合物电子吸收光谱计算显示,低能(近红外和可见光区)的吸收带具有全部或较大的配体→金属电荷转移性质贡献。
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.10804001, No.10674002, and No.20773024）, the National High Technology Research and Development Program of China （863 Program） （No.2006AA09Z243-3）, and the Program for Innovative Research Team in Anhui Normal University of China.
文摘Low-lying electronic states of the lutetium dimer （Lu2） were studied based on density functional theory （DFT） using ten different density functionals together with three different relativistic effective core pseudopotentials （RECPs）. Relative state energies, equilibrium bond lengths, vibrational frequencies, and ground-state dissociation energies were evaluated. It was found that the ground state is a triplet state irrespective of the type of functional and RECP used. This result is in contrast with a previous DFT calculation which gave a singlet ground state for Lu2. By comparing with the high-level ab initio and available experimental results, it is evident that the hybrid-GGA functionals combined with the Stuttgart smallcore RECP yield the best overall agreement for the properties under study. The effects of Hartree-Fock exchange in B3LYP functional on the calculated bond length and dissociation energy of the ground state were examined, and rationalized in terms of 5d participation in Lu-Lu covalent bonding.
文摘经三十余年努力,二价铀溶液化学于近年取得突破性进展,Evans和Meyer等成功获得两个可通过X-ray晶体衍射表征结构的有机金属铀(Ⅱ)配合物.为进一步拓展U~Ⅱ配合物化学和探索可能存在的金属多重键,设计双核配合物[(U~Ⅱ)_2(L)](L为八齿氮供体低聚吡咯大环四价阴离子),并使用相对论密度泛函理论优化其可能的电子自旋态异构体结构和计算相关性质.结果表明,[(U~Ⅱ)_2(L)]具有三重态基态,其电子组态为π~4σ~2δ~2;U(5f)原子轨道对高占据分子轨道有重要贡献;它的U—U键长为2.33?、Mayer键级为3.89和对应的伸缩振动频率为259 cm^(–1),被指认为U—U弱四重键.这一结论与QTAIM(quantum theory of atoms in molecule)的U—U键临界点处的电子/能量密度拓扑分析结果相一致.与不同氧化态铀同类物[(U^m)_2(L)]^(n+)(m=ⅡI,n=2;m=IV,n=4)比较显示,随着铀氧化态增大,U—U距离增长、键级变小、伸缩振动频率变小,金属铀电子自旋密度与常规预期值的差值(?SU)增大;结合分子轨道和QTAIM参数分析,发现金属氧化态可以调控配体和金属轨道能级匹配程度和改变金属-金属多重键.
文摘Since the discovery of the halo nucleus ^(11)Li in 1985,halo phenomena in exotic nuclei have always been an important frontier in nuclear physics research.The relativistic density functional theory has achieved great success inthestudyofhalonucleg,theself-consistent description ofhalonucleusLiandthe microscopic predic tion of deformed halo nuclei.This paper introduces some recent progresses based on the deformed relativistic Hartree-Bogoliubov theory in continuum(DRHBc)and the triaxial relativistic Hartree-Bogoliubov theory in continum(TRHBc).A microscopic and self-consistent description of the deformed halo nucleus ^(37)Mg,including its small one-neutron separation energy,large root-mean-square radius,diffuse density distribution,and p-wave components for the halo neutron,has been achieved by the DRHBc theory.The DRHBc theory has also predicted a deformed neutron halo and the collapse of the N=28 shll closureintherecently discovered isotope ^(39)Na The TRHBc theory has been newly developed and applied to the aluminum isotopic chain.The heaviest odd-odd ^(42)AI has been predicted as a triaxial halo nucleus with a novel shape decoupling between its core and halo at the triaxial level.
