三硝基均苯三酚及其碱金属盐晶体的周期性密度泛函理论研究

对三硝基均苯三酚(TNPG)及其碱金属盐晶体进行DFT-B3LYP周期性计算研究, 求得其能带和电子结构, 探讨了结构-性能关系. 研究结果表明, 晶胞结构参数的计算值与实验值吻合较好. TNPG的导电性介于半导体和绝缘体之间, 而其碱金属盐均为半导体. 金属离子的引入使TNPG阴离子和金属阳离子通过配位键形成三维无限网状结构, 这种网状结构与晶体的半导体性质相关联. TNPG及其碱金属盐的前线轨道主要是由C—NO₂的原子轨道组成, 配位水和金属离子对前线轨道的组成没有贡献. TNPG碱金属盐的带隙均比TNPG的小, 根据“最易跃迁原理”可推测碱金属盐均比TNPG敏感, 这与实验事实相符. 同时, 金属离子的引入增大了酚羟基上的氧原子的活性, 这也可能是导致碱金属盐比TNPG敏感的原因之一.     

磷化镍晶体结构的密度泛函理论研究

运用密度泛函理论系统地研究了已知的磷化镍晶体如Ni3P、 Ni12P5、 Ni2P、 Ni5P4、 NiP、 NiP2 和 NiP3等的结构、成键以及相关的热力学稳定性,对于结构简易化合物（Ni2P和NiP3）的弹性行为进行了预测。这些数据有助于更好的理解磷化镍的催化活性。     

富勒烯C70及Sc3N@C70的密度泛函理论研究

在混合密度泛函B3LYP理论下,用6-31G*基函数对富勒烯C70、它的阴离子及内掺Sc3N富勒烯Sc3N@C70两种同分异构体的几何结构和电子结构进行了研究。计算结果表明,在C70的两种异构体中,满足五元环分离规则(IPR)的C70(D5h)稳定,C70q-(#7854)(q=4,6)比C70q-(D5h)稳定;在Sc3N@C70两种异构体中有三对两两相邻五元环的Sc3N@C70(#7854)稳定,C70(#7854)易于形成富勒烯金属包合物。     

椅型碳纳米管吸附氢原子电子结构的密度泛函研究

采用密度泛函方法对氢原子在(5,5)椅型碳纳米管上的吸附进行了研究, 分别考察了氢原子覆盖度为5%和10%时的构型和吸附能. 研究结果表明, H原子吸附在管外壁要比管内壁能量上更为有利, 同时第二个H原子倾向于吸附在前一个H原子的吸附位置邻近的碳原子上. 由能带计算结果得知, 吸附一个H原子时, 椅型碳纳米管将由导体转变为半导体; 当第二个H原子处在偶数位时, 纳米管仍保持较好的导电性能, 而吸附在奇数位时将使管的传输能力减弱. 本文进一步通过分析纳米管(共轭体系的分布情况对管传输性质的变化进行解释.     

给、吸电子基团对芳香共轭体系电子结构影响的密度泛函理论研究

采用密度泛函理论,在B3LYP／6—31G^＊方法水平上对8个连接有给、吸电子基团的芳香共轭体系的稳定性、偶极矩、静电荷分布和前线轨道能级进行了研究,并采用TD／DFT方法进一步研究了它们的电子光谱．结果表明a-1,b-1,c-1和d-2分子比它们的同分异构体要稳定;对于苯、呋喃、吡咯与乙烯形成的共轭体系,吸电子基团连接在乙烯一端,给电子基团连接在芳香环上使体系的偶极距增强,而吡啶则相反;前线轨道能级差较小的是吸电子基团连接在芳香环一端的体系,相应的分子最大吸收波长也较大．     

Nb@C_(36)结构和性能的密度泛函研究

用密度泛函方法,采用GGA/PW91方法对具有D6h对称性的C36及其衍生物Nb@C36进行结构优化和性能计算,探讨Nb@C36稳定构型;存在的可能性及稳定性;以及Nb掺杂对C36结构及性能的影响.结果表明,Nb位于C36主轴上偏离中心0.1 nm时,Nb@C36能量最低,结构最稳定;Nb掺杂引起笼的局部畸变,但Nb@C36仍保持完整笼型结构.Nb@C36稳定性较C36有所提高,具有存在的可能性.Nb原子嵌入C36使其禁带宽度略有减小,导电性及化学反应活性有所提高;费米能级下降,但仍处于禁带之间,二者均属半导体性质的材料.C36结构及性能的变化与Nb所处的位置及Nb与C36笼之间的电子迁移有关.     

黄酮类化合物的密度泛函理论研究

在混合密度泛函B3LYP理论下,用6-31G*基函数研究了几种典型黄酮类化合物分子的几何结构、电子结构和分子的静电势,讨论了电子结构和分子活性部位的关系.     

密度泛函理论模拟外电场对铁氧体电子结构的影响

通过密度泛函理论(DFT)模拟了3种典型的铁氧体(Fe₂O₃、Fe₃O₄和α-FeOOH)受外电场作用下的电子结构，研究了外电场对不同铁氧体电子结构的影响。DFT模拟结果显示：外电场的存在能够有效提高Fe₂O₃、Fe₃O₄和α-FeOOH晶体结构的价带位置，从而导致3种铁氧体的带隙出现明显的降低；当外电场强度为0.01 V·nm^-1时，Fe₂O₃、Fe₃O₄和α-FeOOH的带隙分别降低了0.36、0.12和0.34 eV；当电场增大至0.1 V·nm^-1时，Fe₂O₃晶体出现击穿现象，Fe—O化学键断裂导致Fe原子的电子沿外电场方向高度离域至相邻Fe原子，而Fe₃O₄和α-FeOOH则仅出现不同价带能级电子局域性增强且能量同质化，因而显示出相对稳定的物理化学结构。此外，外电场的存在可导致3种铁氧体价带电子均出现简并现象，且随电场强度增大而增强。3种铁氧体中，外电场的存在导致Fe₂O₃晶体中Fe原子的电荷密度增大而降低O原子的电荷密度； Fe₃O₄晶体结构中不同配位结构的Fe原子以及配位O原子的Hirshfeld电荷几乎不受外电场的影响； α-FeOOH晶体中共边FeO₆配位结构的Hirshfeld电荷受外电场影响较小，而共角FeO₆配位结构的Hirshfeld电荷受外电场影响较大，且H原子的电荷在强外电场作用下发生歧化响应。随着外电场强度逐渐增大，Fe₃O₄晶体的电子自旋态密度逐渐增大，而α-FeOOH晶体的电子自旋态密度则显示出降低的规律。     

密度泛函理论模拟外电场对铁氧体电子结构的影响

通过密度泛函理论(DFT)模拟了3种典型的铁氧体(Fe₂O₃、Fe₃O₄和α-FeOOH)受外电场作用下的电子结构,研究了外电场对不同铁氧体电子结构的影响。DFT模拟结果显示:外电场的存在能够有效提高Fe₂O₃、Fe₃O₄和α-FeOOH晶体结构的价带位置,从而导致3种铁氧体的带隙出现明显的降低;当外电场强度为0.01 V·nm^-1时,Fe₂O₃、Fe₃O₄和α-FeOOH的带隙分别降低了0.36、0.12和0.34 eV;当电场增大至0.1 V·nm^-1时,Fe₂O₃晶体出现击穿现象,Fe—O化学键断裂导致Fe原子的电子沿外电场方向高度离域至相邻Fe原子,而Fe₃O₄和α-FeOOH则仅出现不同...     

砷原子团簇结构的量子化学密度泛函理论研究

采用密度泛函理论的三种方法:局域自旋密度近似SVWN、梯度修正BLYP、杂化密度泛函B3LYP,优化了中性Asn、负离子Asn-(n=2～5)的结构,在优化结构基础上计算了它们的振动光谱,获得它们稳定的最低能量态的结构.其中中性Asn(n=2～5)的稳定结构的计算结果,与已有的理论结果以及实验数据进行了比较.而对负离子Asn-(n=2～5))的稳定结构作了预言.同时计算了Asn(n=2～5)的绝热电子亲和能(EAa),与有关光电子谱学的实验值符合较好.     

TATB固体与表面吸附水的相互作用研究

TATB（1，3，5-三氨基-2，4，6-三硝基苯）是最著名的耐热钝感炸药；水在 TATB表面的吸附作用研究具有理论和实用双重意义。在B3LYP/6-31G~（**）水平上 ，在对TATB晶体（001）表面作周期性计算的基础上经基组叠加误差（BSSE）校正 ，求得TATB的表面能为-19.90 kJ·mol~(-1)，与实验值良好相符；首次求得水在 TATB（001）面的吸附能为-10.25kJ·mol~(-1)；重点讨论了吸附前后能带和电子 结构的变化。     

DFT in a nutshell

The purpose of this short essay is to introduce students and other newcomers to the basic ideas and uses of modern electronic density functional theory, including what kinds of approximations are in current use, and how well they work (or not). The complete newcomer should find it orients them well, while even longtime users and aficionados might find something new outside their area. Important questions varying in difficulty and effort are posed in the text, and are answered in the Supporting Information. © 2012 Wiley Periodicals, Inc.     

On the DFT Ground State of Crystalline Bromine and Iodine

We report on an erroneous ground state within common density functional theory (DFT) methods for the solid elements bromine and iodine. Phonon computations at the GGA level for both molecular crystals yield imaginary vibrational modes, erroneously indicating dynamic instability—that fact alone could easily pass as a computational artefact, but these imaginary modes lead to energetically more favorable and dynamically stable structures, made up of infinite monoatomic chains. In contrast, meta‐GGA and hybrid functionals yield the correct energetic order for bromine, while for iodine, most global hybrids do not improve the GGA result significantly. The qualitatively correct answer, in both cases, is given by the long‐range corrected hybrid LC‐ωPBE, the Minnesota functionals M06L and M06, and by periodic Hartree–Fock and MP2 theory. This poor performance of economic DFT functionals should be kept in mind, for example, during global structure optimizations of systems with significant contributions from halogen bonds.     

钾搀杂对叠氮化亚铜晶体能带结构影响的DFT研究

运用广义梯度近似(GGA)密度泛函理论（DFT）方法对钾搀杂叠氮化亚铜晶体的原子和电子结构以及缺陷形成能进行了研究。结果表明,钾搀杂破坏了叠氮酸根的对称性,导致不对称的原子位移。随着搀杂钾浓度的增加,搀杂叠氮化亚铜晶体的带隙逐渐增大。热力学上,杂质钾很容易被搀杂到叠氮化亚铜晶体中,而且钾还充当了缺陷团簇的成核中心。最后,从电子结构角度理解了搀杂钾浓度对叠氮化亚铜晶体感度的影响。     

Ab initio Study of Electronic Structure and Properties in Crystalline 1,1,3,3,5,5‐Hexaazidocyclotriphosphazene

The banding and electronic structures of crystalline 1,1,3,3,5,5‐hexaazidocyclotriphosphazene (P₃N₂₁) have been investigated at DFT‐B3LYP/6‐31G(d) level. Relaxed crystal structure compares well with experimental data. The energy gap is 5.57 eV, indicating that P₃N₂₁ is an insulator. The frontier orbital is mainly formed by atomic orbitals of azido group, so it is the most reactive part of the molecule. The intermolecular interaction is strong along the direction that is nearly perpendicular to the phosphazene ring. The distribution of electrostatic potential is quite uneven, so P₃N₂₁ has a very high impact sensitivity. The point charge electrostatic potential is very high between the azido groups of the neighboring molecules, which indicates that the crystal lattice in this position may easily be broken and becomes the explosion center when P₃N₂₁ is impacted. The overlap populations of P–N_α bonds are much less than those of other bonds, therefore the P–N_α bonds first rupture by external stimuli, which agrees well with the experimental study of mass spectrum.     

Metallobiliverdin Radicals—DFT Studies

Several aspects of the molecular and electronic structure of biliverdin derivatives have been studied using density functional theory (DFT). The calculations have been performed for complexes of trianion (BvO₂)^3? and dianion [BvO(OH)]^2?, derived from two tautomeric forms of biliverdin, BvO₂H₃ and [BvO(OH)]H₂, with redox innocent metal ions: lithium(I ), zinc(II ), and gallium(III ). One‐electron‐oxidized and ‐reduced forms of each complex (cation and anion radicals) have been also considered. The molecular structures of all species investigated are characterized by a helical arrangement of tetrapyrrolic ligands with the metal ion lying in the plane formed by the two central pyrrole rings. The spin density distribution in four types of metallobiliverdin radicals—[(BvO₂^.)Mⁿ⁺]^n‐2, [{BvO(OH)^.}Mⁿ⁺]^n‐1 (cation radicals), [(BvO2^.)Mⁿ⁺]^n‐4, [{BvO(OH)^.}Mⁿ⁺]^n‐3 (anion radicals)—has been investigated. In general, the absolute values of spin density on meso carbon atoms were larger than for the β‐carbon atoms. Sign alteration of spin density has been found for meso positions, and also for the β‐carbon atoms of at least two pyrrole rings. The calculated spin density maps accounted for the essential NMR spectroscopic features of iron biliverdin derivatives, including the considerable isotropic shifts detected for the meso resonances and shift alteration at the meso and β‐positions.     

TATB二聚体分子间作用力及其气相几何构型研究

采用对称性匹配微扰理论(SAPT)定量地求得TATB分子间的静电、交换排斥、诱导和色散等分子间作用能项, 从理论上揭示了TATB分子间作用本质; 在此基础上, 阐明了密度泛函在研究TATB二聚体时的适合性问题. 结果表明: (1)在有分子间氢键的TATB二聚体中, 库仑力足以与交换排斥力相抗衡, 起主导作用. (2)含分子间氢键的气相TATB二聚体的合理几何构型为平面型结构, 此结构的产生与色散力无关, 因此不管泛函是否含有近程色散作用, 均应预测到这种强极性的平面型结构. (3)在无分子间氢键的TATB二聚体中, 库仑力难以与交换排斥力相抗衡, 色散作用起到了关键作用; (4)在这种情况下, 未含有近程色散作用的密度泛函不可能给出合理构型. 恰好相反, 含有近程色散作用的密度泛函PBE0却能正确地预测到具有“平行重叠”结构且呈微弱极性的TATB二聚体, 色散力是导致这种构型产生的根本原因. “平行重叠”TATB二聚体是典型的色散体系, 其色散力占绝对主导地位并极有可能起源于两个TATB分子上π电子的相互作用. (5)对于所有TATB二聚体, 色散力或很显著或起主导作用. 由于密度泛函或未含有近程色散, 或只能部分地把近程色散表达出来, 这样使得当前所有密度泛函不可能精确求得这些二聚体的作用能.     

A DFT Study on the Structure and Properties of Cu/Cr2O3 Catalyst

Using DFT method, the stable adsorption configurations of Cu₄ cluster on Cr₂O₃ (0001) surface were investigated. The regular tetrahedron structure and the planar structures were considered as the initial adsorption configuration of Cu₄ cluster, respectively. The adsorption energies of the two structures were also calculated. The simulation result indicated that the adsorption energy of the regular tetrahedron structure was higher than that of the planar structure, and thus the regular tetrahedron structure was confirmed to be the stable adsorption configuration for Cu₄ cluster on Cr₂O₃ (0001) surface. Moreover, it was observed that the Cu₄ cluster showed the definite stable adsorption sites on Cr₂O₃ (0001) surface, namely 3‐fold O sites. During the adsorption process of Cu₄ cluster onto Cr₂O₃ (0001) surface, the Cu₄ cluster could bond with more Cr or O atoms on the surface, and the apparent charge transfer also occurred correspondingly. Meanwhile, the Cu₄ cluster and Cr₂O₃ (0001) surface would bond in the form of local polarization to enhance the stability of adsorption configuration.     

Structure and vibrational spectra of dicyclopentadienylzinc. A DFT study

The quantum-chemical DFT calculations of the Cp₂Zn structure confirm the conclusion made earlier from the vibrational spectra that the sandwich structure (⁵-C₅H₅)₂Zn (A) is not energetically favorable and more favorable are the close in energy -structure (⁵-C₅H₅)(¹-C₅H₅)Zn (B) and -structure (¹-C₅H₅)₂Zn (C). The vibrational spectra of structures B and C with the DFT-derived force fields were calculated. A comparison of the calculated spectra of the isolated Cp₂Zn molecules with the experimental data gives no way of deciding between the B and C structures. It is most likely that the molecule is nonrigid and experiences a strong influence from the nearest environment in solution or in the crystalline state.