Periodic DFT investigation on the structure and properties of TNAD crystal

Density function theory calculations were performed at the GGA/PW91, GGA/PBE, and LDA/CA‐PZ levels to study the structures and properties of the crystalline TNAD (trans‐1,4,5,8‐tetranitrotetraazadecalin). The relaxed crystal structure compares well with the experimental data. Analysis on the band structures shows that the frontier energy bands are generally quite flat, and the energy gap between the highest occupied crystal orbital and the lowest unoccupied crystal orbital is about 3.4 eV, indicating that the crystal is an electrical insulator. All the atoms of TNAD make up both the lower and the higher energy bands. The projection of density of state demonstrates that the N? NO₂ bond is the most reactive region of the material. The lattice energy is predicted to be ?155.13 kJ/mol at the LDA/CA‐PZ level, consistent with the previous studies, whereas it is underestimated by the GGA/PW91 (?70.41 kJ/mol) and GGA/PBE (?74.33 kJ/mol). The optical properties under ambient condition were investigated, including dielectric function, absorption coefficient, and reflectivity. The calculated absorption spectra show a number of absorption peaks in the fundamental absorption region, which are believed to be associated with different exciton states. And the reflectivity spectra are mainly composed of four peak structures, where the magnitude changes in the order of GGA/PBE < GGA/PW91 < LDA/CA‐PZ on the whole. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

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.     

O掺杂MgF2电子结构和光学性质的第一性原理研究

基于密度泛函理论(DFT)的第一性原理平面波超软赝势方法,计算了O原子不同比例(12.5％,8.33％和6.25％)掺杂MgF2晶体的几何结构、电子结构和光学性质.通过对比发现,由于O原子的掺入,体系的禁带宽度减小,材料呈现半金属性.计算也表明,O掺杂对静态介电常数和光吸收系数有重要调制作用,同时也给出了体系性质变化的...     

六硝基六氮杂三环十二烷二酮的密度泛函理论研究

对迄今为止爆速最高的高能化合物六硝基六氮杂三环十二烷二酮(HHTDD)的结构和性质实现了DFT-B3LYP/CEP-31G水平的计算研究。其全优化几何构型中六员氮杂环可取椅式和船式2种构象,并以船式构象更稳定。基于集居数、自然键轨道(NBO)、分子总能量和前线轨道能量等电子结构参数对该化合物若干性质进行了探讨。尤其揭示了分子中NNO2键所表现出的最大活性。在振动分析的基础上求得273～800 K温度范围内体系的热力学性质。从理论上预测的爆速与实测值相吻合。     

Ion-pair charge transfer complexes with intense near IR absorption: Syntheses,crystal structures,electronic spectra and DFT calculations

Five ion-pair complexes, consisting of R-benzylidene-1-aminopyridinium derivatives and [Ni(mnt)₂]²⁻ (R = p-nitro (1), p-methyl (2), p-bromo (3), p-chloro (4) and m-nitro (5); mnt²⁻ = maleonitriledithiolate), were synthesized and structurally characterized. As for 1, it is interesting to observe a large deviation from square-planar coordination geometry for the Ni atom, while no deviation is observed in the other four complexes. In the solid state, UV–Vis–NIR spectra of 2–5 show similar properties with intense absorption in the 200–750 nm and moderate near IR absorption in the 750–1000 nm region, whereas 1 exhibits an intense absorption from UV/Visible to near-IR region (200–1100 nm). This unique spectral feature of 1 is attributed to its distinctive structural differences from 2 to 5, namely the strong intermolecular packing interactions between anions and cations, as well as a significant deviation from the planarity of the anion. Based on DFT and TDDFT calculations, near-IR absorbance bands in 1–5 were assigned to combined transitions of d–d, MLCT and π–π^∗ in the [Ni(mnt)₂]²⁻ anion as well as the ion-pair charge transfer (IPCT) from the anionic HOMO to the cationic LUMO. The IPCT band position in acetonitrile is independent of the substituent group feature in benzene ring of cations for 1–5, which could be interpreted that the substituent group in benzene ring only has a minor contribution to the cationic LUMO.     

Ab initio Study on the Molecular Geometry,Electronic Structure and Thermodynamic Properties of Benzotrifuroxan(BTF)

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Ab initio Study on the Molecular Geometry,Electronic Structure and Thermodynamic Properties of Benzotrifuroxan(BTF)

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High active amorphous Co(OH)2 nanocages as peroxymonosulfate activator for boosting acetaminophen degradation and DFT calculation

Acetaminophen(ACE)is commonly used in analgesic and antipyretic drug,which is hardly removed by traditional wastewater treatment processes.Herein,amorphous Co(O...     

碳掺杂硼氮纳米管导电性的理论研究

根据DFT/B3LYP的计算结果,从能带、态密度和电子结构的变化,讨论了以C_C键替换B_N键的二碳和四碳掺杂的硼氮纳米管的导电性.结果表明,替换后硼氮纳米管的导电性能增强,并且可以通过控制替换的量来调节管的半导体性能     

DFT Simulations as Valuable Tool to Support NMR Characterization of Halide Perovskites: the Case of Pure and Mixed Halide Perovskites

Solid state NMR spectroscopy is swiftly emerging as useful tool to characterize the structure, composition and dynamic properties of lead halide perovskites. On the other hand, interpretation of solid state NMR signatures is often challenging, because of the potential presence of many overlapping signals in small range of chemical shifts, hence complicating the extraction of detailed structural features. Here, we demonstrate the reliability of periodic Density Functional Theory in providing theoretical support for the NMR characterization of halide perovskite compounds, considering nuclei with spin I=1/2. For light ¹H and ¹³C nuclei, we predict NMR chemical shifts in good agreement with experiment, further highlighting the effects of motional narrowing. Accurate prediction of the NMR response of ²⁰⁷Pb nuclei is comparably more challenging, but we successfully reproduce the downshift in frequency when changing the halide composition from pure iodine to pure bromine. Furthermore, we confirm NMR as ideal tool to study mixed halide perovskite compounds, currently at the limelight for tandem solar cells and color-tunable light emission.     

NbC固体表面能带和电子结构的理论研究

采用DFT/BLYP方法对NbC(001)和(111)面的电子结构进行研究。计算结果表明,对于NbC(001)表面,其表面态主要集中于费米能级(EF)下方约4.5eV附近区域,并以表面Nb原子和C原子为主要成分。O2分子在该表面吸附时,趋向于吸附在表面Nb原子上。对于NbC(111)表面,其表面态集中在EF下方0.02.0eV区域,靠近EF的态具有较高的表面活性,其主要成分为表面Nb原子的4dxz/dyz成分。上述结论与光电子能谱实验结果基本一致;但由于金属原子d电子数的差异导致NbC(111)表面态成分与类似的TiC化合物并不相同。     

Synthesis,spectroscopy, X-ray crystal structure,and DFT studies on a platinum(II) Schiff-base complex

[PtCl₂(SMe₂)₂] reacts with (N,N′-bis(salicylidene)-1,2-cyclohexanediamine) to give (N,N′-bis(salicylidene)cyclohexane-1,2-diamine)platinum(II). The complex has been characterized by elemental analysis, infrared (IR), UV-Vis, and single-crystal X-ray diffraction. Pt(II) is in a square-planar environment, coordinated by a chelating N₂O₂ donor. Density functional theory (DFT) calculations such as geometry optimization, vibrational frequency, electronic properties, and natural bond orbital (NBO) have been performed for the platinum compound using the OLYP method at TZP(6-311G*) basis set. The optimization calculation shows that the geometry parameters can be reproduced with the OLYP/TZP basis set. Experimental IR frequencies and calculated vibrational frequencies support each other. Time-dependent DFT has been used for absorption wavelengths and results were compared with experimental data. Moreover, NBO analysis has been performed.     

多溴代二苯胺热力学性质的密度泛函理论研究

在B3LYP/6-31G*水平上对209个多溴代二苯胺(PBDPA)系列化合物进行了全优化和振动分析计算, 得到各分子在298.15 K, 101.3 kPa标准状态下的热力学参数. 设计等键反应, 计算了PBDPA系列化合物的标准生成热(ΔfHÖ)和标准生成自由能(ΔfGÖ). 研究了热力学参数SÖ与溴原子的取代位置及取代数目(NPBS)之间的关系, 结果表明: PBDPA系列化合物的SÖ, ΔfHÖ和ΔfGÖ与NPBS之间有很强的相关性(R2≥0.984). 根据异构体标准生成自由能的相对大小, 从理论上求得异构体的相对稳定性. 以Gaussian 03程序的输出文件为基础, 采用统计热力学程序计算了PBDPA化合物在200 K至1000 K的摩尔恒压热容(Cp,m), 并用最小二乘法求得Cp,m与温度之间的相关方程, 发现Cp,m与T, T－1和T－2之间有着很好的相关性(R2＝1.000).     

Synthesis, crystal structure and DFT analysis of a new trinuclear complex of copper

The new trinuclear complex [Cu₂(μ-L)₂CuCl₂] has been synthesized and characterized by elemental analysis, IR, UV-Vis and X-ray spectroscopy, where L is a dianionic tetradentate Schiff base ligand with N₂O₂ donor atoms. The molecular structure of [Cu₂(μ-L)₂CuCl₂] was determined by X-ray crystallography. In the complex, the most remarkable aspect of the trinuclear complex is that it adopts a bent structure for the three copper atoms, with a Cu1Cu3Cu2 intramolecular angle of approximately 90.62(2)°. All three copper atoms are five coordinate, with a slightly distorted square pyramidal geometry. In the two terminals moieties, the basal plane of the square pyramidal is formed by two oxygen atoms and two nitrogen atoms of the Schiff base ligand, and the apical position at the Cu atom is occupied by the bridging Cl1 anion. The Cu1Cl1Cu2 angle is 110.51(5)°. The central copper atom also has a five-coordinate, slightly distorted square pyramidal geometry, with four phenolato oxygens belonging to the Schiff base ligands from Cu(salpn) units describing the square planar base and the Cl anions being apical. The optimized structure of the complex has been studied using the B3LYP/6-31G(d)/LanL2TZf level of theory. The calculation shows that all the copper atoms are five coordinate with distorted square pyramidal structures, which is consistent with experimental data.     

C_(36)聚合体电子结构的理论研究

采用PM3 和DFT/B3LYP方法对2D六方网状,以及1D链状C36聚合体的构型进行全优化,探讨了其电子结构和稳定性;并在从头算水平上计算了相应的能带结构。研究发现,C36形成聚合体后构型发生了显著变化; 与0D 的结构比较,C36聚合为1D或2D结构后,笼内CC键长变化明显。计算表明C36聚合后稳定性提高,呈半导体或绝缘体性质。聚合后C36内部CC键定域化程度的增强是其稳定性提高的主要因素。     

Chemical Bonding in Molecules and Complexes Containing d-Elements Based on DFT

Summary. Metal–ligand bonding in transition metal halide molecules and complexes with different central ions, oxidations states, and coordination numbers: Cr^IIIX₆^3–, Cr^IVX₄, Cr^IIX₂ (X = F,Cl,Br,I), M^IIICl₆^3–(M = Mo,W), M^III(H₂O)₆³⁺(M = Cr,Co) and Re₂Cl₈^2– has been studied in terms of the Extended Transition State (ETS) energy patitioning scheme within the DFT and electron density analysis (the Laplacian of the electron density and the electronic localization function). Bonding is found to be dominated by ionicity in all cases, especially so for complexes with higher coordination numbers. Covalent contributions to the metal–ligand bond are found to be mainly due to the nd-electrons and to lesser extent due to the metal (n+1)s and (n+1)p-orbitals, contributions from (n+1)s increasing when going to lower coordination numbers. Metal–ligand bonding analysis have been used in order to check some concepts emerging from ligand field theory when applied to the spectroscopy and magnetism of transition metal complexes. It is pointed out that for complexes of high symmetry (MX₆, O_h, MX₄, T_d, and MX₂, D_h) electron density analyses gain interpretative power when partitioned into contributions from occupied orbitals of different symmetry.     

多氯代吩噁嗪热力学性质的密度泛函理论研究

在B3LYP/6-31G*水平上对135个多氯代吩噁嗪(PCPXs)系列化合物进行了全优化和振动分析计算, 得到各分子在298.15 K, 1.013×105 Pa标准状态下的热力学性质. 设计等键反应, 计算了PCPXs系列化合物的标准生成热(Δf )和标准生成自由能(Δf ), 研究了这些参数与氯原子的取代位置及取代数目(NPCS)之间的关系, 结果表明: 熵( )、Δf , Δf 与NPCS之间有很强的相关性. 根据异构体标准生成自由能的相对大小, 从理论上求得异构体的相对稳定性. 以Gaussian 03程序的输出文件为基础, 采用统计热力学程序计算了PCPXs化合物在200 K至1800 K的摩尔恒压热容(Cp,m), 并用最小二乘法求得Cp,m与温度之间的相关方程, 发现Cp,m与T, T－1和T－2之间有着很好的相关性.     

1,1′-联萘-2,2′-二胺的结构和外消旋机理的DFT研究

运用电子密度泛函理论(DFT)研究了1,1′-联萘-2,2′-二胺光学构象的稳定性、消旋异构化过程及机理。研究表明:2,2′-BINAM有三种稳定构型,每一种构型都有两个镜面对映异构体。2,2′-BINAM的异构化有两种类型:一是氨基围绕离域大π键所在平面进行翻转;另一是两个萘环围绕C1-C1′键进行旋转。     

Coordination of reduced Schiff base anion to Pd(II): Synthesis,characterization, DFT calculation and catecholase activity

The article reports the synthesis and characterization of a new palladium(II) complex of type [(L_NNN¹⁻)PdCl] (1) where L_NNN¹⁻ is a mono anionic Schiff's base having a imine bond in reduced state. The L_NNN¹⁻ is generated from a tridentate NNN donor ligand (L_NNN) through in-situ reduction using sodium borohydride, where L_NNN is [(E)-N-(phenyl(pyridine-2-yl)methylene)quinoline-8-amine)]. 1 is characterized by the single crystal X-ray diffraction study, IR, mass and UV–Vis spectroscopy. The X-ray bond parameter authenticates the imine bond of the coordinated Schiff's base anion is in reduced state. 1 exhibits catalytic activity towards the oxidation of 3,5-ditertiarybutyl catechol(3,5-DTBC) with turnover number (K_cat) ​= ​135.6 h^-1. The catalytic oxidation of 3,5-DTBC is authenticated by the UV–Vis, mass and EPR spectroscopy. An isotropic EPR signal with g ​= ​2.011 of a solution containing 1 and 3,5-DTBC authenticating the generation of organic radical during the oxidation process. Cyclic voltammogram of 1 displays an irreversible anodic wave at +0.22 ​V may be due to the oxidation of N⁻ to N^•−. The atomic spin density of 1⁺ obtained from DFT calculation is also supporting the N-centre oxidation process.