团簇As4S与As4Se稳定性与芳香性的理论研究

结合密度泛函和二级微扰理论,对As4S和As4Se团簇进行结构优化和频率分析.结果表明两者基态都采取单重态平面五角形构型(C2v,1A1)。分子轨道分析表明每个基态都有三个双电子占据的、高度离域的π型价分子轨道,符合4N+2芳香性电子规则。所有相邻As–As、As–M(M=S,Se)键的Wiberg键级(自然键轨道分析)和键长都处于相应单、双键数值之间;预测的各向异性磁化率和核独立化学位移都为较大负值,以上证据充分表明As4S和As4Se基态都表现出强芳香性。     

四唑与水二聚体相互作用的理论研究

在DFT—B3LYP／6—311＋＋G^＊＊水平下,求得1H-四唑和2H-四唑与水的二聚体势能面上4种优化几何构型和电子结构。并求得4种四唑单体与水二聚体在B3LYP／6—311＋＋G6＊＊水平下的BSSE分别为：3．95,2．52,2．57和4．03kJ／mol,ZPE校正能量分别为7．00,5．27,4．04和5．93kJ／mol。经基组叠加误差（BSSE）和零点能校正后,1H-和2H-四唑／水二聚体分子间最大相互作用能为-37．68kJ／mol。电荷分布与转移分析表明,二子体系间的电荷转移很少,但接触点上氮原子和氢原子电荷变化较大。由自然键轨道（NBO）分析揭示了分子间相互作用的本质。     

DNGTz二聚体分子间相互作用的密度泛函理论计算

在DFT-B3LYP/6-31G*水平下,求得3,6二硝基胍基-1,2,4,5-四嗪(DNGTz)二聚体势能面上9种优化几何构型和电子结构.用基组叠加误差(BSSE)和零点能(ZPE)校正,计算了分子间相互作用能,二聚体分子间最大相互作用能为-62.24 kJ/mol.由自然键轨道(NBO)分析揭示了分子间相互作用的本质.对优化构型进行振动分析,并基于统计热力学求得温度200.0～800.0K从单体形成二聚体的热力学性质变化.结果表明,二聚主要由强氢键所贡献,而结合能不仅取决于氢键.二聚体Ⅰ、Ⅲ、Ⅳ、Ⅴ和Ⅶ的二聚过程在200.0K均能自发进行,表明二聚体Ⅰ、Ⅲ 、Ⅳ、Ⅴ和Ⅶ在室温可以稳定存在.     

功能化离子液体1-(3-磺酸)丙基-3-甲基咪唑硫酸氢盐[HSO3-(CH2)3-mim][HSO4]的微观结构及阴阳离子之间的相互作用

采用密度泛函理论(DFT)的B3PW91/6-311+ G(d)方法,对Br(o)nsted酸功能化离子液体1-(3-磺酸)丙基-3-甲基咪唑硫酸氢盐[HSO3-(CH2)3-mim][HSO4]进行了结构优化、频率分析和自然键轨道(NBO)分析.离子对的微观结构及其原子电荷分布和电荷转移情况表明阴阳离子之间存在较强的...     

Insights into the confinement effect on isobutane alkylation with C4 olefin catalyzed by zeolite catalyst: A combined theoretical and experimental study

Elucidating the confinement effect harbours tremendous significance for isobutane alkylation with C₄ olefin. Herein, the confinement effect over zeolite catalysts was elucidated by combining DFT calculations, experiments(using the novel Beta zeolite exposing only external surfaces(Beta-E) and conventional Beta-I zeolite with both external and internal surfaces) and multi-techniques(e.g., TGA-DTG,HRTEM, SEM and XRD). It is found that the main active sites for C₄ alkylation r...     

1-(2-羟基)乙基-3-甲基咪唑溴盐(HEMIMB)的微观结构及阴阳离子之间的相互作用

采用密度泛函理论B3PW91/6-31+G(d)方法,对1-(2-羟基)乙基-3-甲基咪唑溴盐(HEMIMB)离子液体进行了结构优化和频率分析,得到了离子对的最稳定结构。离子对的几何参数表明阴阳离子之间存在较强的氢键相互作用。自然键轨道(NBO)理论分析离子对中的原子电荷分布和电荷转移情况,结果表明离子对中阴阳离子间存在静电相互作用和氢键作用,而最稳定的离子对主要是源于Br的孤对电子与羟基之间的氢键相互作用。     

Theoretical conformational study of 1,1,1-trifluoro-4-mercapto-but-3-ene-2-thione and the importance of intramolecular hydrogen bonding in ground and first electronic excited state

Quantum chemical calculations of energies, geometrical structure, intramolecular hydrogen bonding (HB) and vibrational frequencies of 1,1,1-trifluoro-4-mercapto-but-3-ene-2-thione were carried out by the ab initio Hartree–Fock, Moller–Plesset second-order perturbation (MP2) and density functional theory (DFT) methods with 6-311++G** basis set in gas phase and water solution. The nature of the intramolecular hydrogen bond in the most stable chelated conformers has been studied by using the atoms in molecules theory of Bader, which is based on topological properties of the electron density. Natural bond orbital (NBO) analysis was also performed for better understanding of the nature of intramolecular interactions. The influence of the solvent on the stability order of conformers and the strength of intramolecular HB was considered using Tomasi's polarized continuum model. The HOMA, NICS, PDI, ATI, FLU and FLU _π indices as well-established aromaticity indicators are examined. The excited-state properties of intramolecular HB in hydrogen-bonded systems have been investigated theoretically using the time-dependent DFT method. The calculated highest occupied molecular orbital (MO) and lowest unoccupied MO with frontier orbital gap are presented. Further verification of the obtained transition state structures was implemented via intrinsic reaction coordinate analysis.     

三联吡啶衍生物Hg2+探针的合成、离子识别及量化计算

通过Suzuki偶联反应,分别将9-己基-9H-咔唑基团和三苯胺基团引入4'-(4-苯基)-2,2',6',2″-三联吡啶结构中,设计合成了两种具有D-π-A结构的三联吡啶衍生物(Tpy1和Tpy2),并经熔点、核磁共振、质谱及元素分析对其结构进行了表征。Tpy1和Tpy2对Hg2+比其他金属阳离子具有更好的选择性,可通过紫外分光光度法或紫外灯下肉眼观测对二氯甲烷溶液中的Hg~(2+)进行有效识别。密度泛函理论(DFT)量化计算结果表明,当探针与Hg~(2+)结合后,其分子内电荷转移(ICT)效应增强,吸收光谱红移31 nm。此外,探针分子中所连接的不同的供电子芳香基团可影响其对Hg~(2+)的识别效果,Tpy1和Tpy2检测限分别为2.51×10~(-6)mol/L和4.40×10~(-6)mol/L。探针分子对Cu~(2+)也有响应。     

Experimental and theoretical study on a novel supramolecular complex constructed from benzenetetracarboxylatic acid and 1,2,3,4-tetra(4-pyridlyl)thiophene

Hydrothermal reaction of benzenetetracarboxylatic acid (H₄BTC) with 1,2,3,4-tetra(4-pyridlyl)thiophene (TPT) afforded a novel supramolecular complex [(H₄BTC))(TPT)]_n (1), which was characterized by FT-IR spectroscopy, elemental analysis, luminescence and thermogravimetric analysis. X-ray single-crystal diffraction reveals that 1 exhibits a one-dimensional (1-D) wave-shape chain assembled through strong hydrogen bonds. Density functional theory (DFT) calculations show that the optimized structures closely resemble the experimental structures. The electronic absorption spectrum of the model dimer in its singlet state has been studied by a time-dependent DFT (TD-DFT) calculation and the nature of the molecular orbitals involved in the fluorescent property was verified.     

Experimental and Theoretical Study of O-Substituent Effect on the Fluorescence of 8-Hydroxyquinoline

The synthesis and characterization of different ether and ester derivatives of 8-hydroxyquinoline have been made. UV-visible and fluorescence spectra of these compounds have revealed spectral dependence on both solvent and O-substituent. The fluorescence intensity of ether derivatives revealed higher intensity for 8-octyloxyquinoline compared with 8-methoxyquinoline, whereas those of ester derivatives had less fluorescence than 8-hydroxyquinoline. Theoretical calculations based on Time-dependent density functional theory (TD-DFT) were carried out for the quinolin-8-yl benzoate(8-OateQ) compound to understand the effect of O-substituent on the electronic absorption of 8-hydroxyquinaline (8-HQ). The calculations revealed comparable results with those obtained from the experimental data. Optimized geometrical structure was calculated with DFT at B3LYP/6-311++G** level of theory. The results indicated that 8-OateQ is not a coplanar structure. The absorption spectra of the compound were computed in gas-phase and solvent using B3LYP and CAM-B3LYP methods with 6-311++G ** basis set. The agreement between calculated and experimental wavelengths was very good at CAM-B3LYP/6-311++G** level of theory.     

Designing polysulfides adsorption-conversion on g-C3N4-based separator via doping heteroatoms boron and phosphorus toward high-performance lithium-sulfur batteries

The notorious “shuttle effect” of lithium polysulfides (LiPSs) has suppressed the large-scale commercial application of lithium-sulfur batteries (LSBs). Also, the intrinsic advantages including inhibiting the shuttling-circulation and promoting the conversion of LiPSs, on the separator are deemed as stimulating blocks on the exploitation of LSBs. Herein, guided by theoretical calculations, we have designed doping-heteroatoms boron (B) and phosphorus (P) on graphitic carbon nitride (g-C₃N₄), to suppress the “shuttle effect” of LiPSs and improve the battery cycling performance. Theoretical calculations show strong chemical bonding between Li atom and N substance of g-C₃N₄, and corroborates synergistic mechanism of electron transfer and van der Waals interaction. The high adsorption energies with doping B/P atoms enable LiPSs adsorption on the separators inhibiting shuttle loss. As expected, the experiment data also demonstrate that superior electrochemical performance are achieved by utilizing B-doped g-C₃N₄ (BCN) separator. Incorporating the B-doped g–C₃N₄ (BCN) separator in LSBs delivered an initial specific capacity of 1050 mAh g⁻¹ at 1 C and 920 mAh g⁻¹ at 2 C. Notably, it achieved a decay rate of 0.08% and 0.1% at 1 and 2 C, respectively, after 500 cycles. This study furthers our understanding of B/P doping separator enhancement and restraining LiPSs shuttling loss for an improved LSBs performance.     

The novel material based on strandberg-type hybrid complex (C6H10N2)2[Co(H2O)4P2Mo5O23].6H2O: Experimental and simulations investigation on electronic,optical, and magnetocaloric properties

The hybrid Strandberg complex materials have attracted intensive interest due to their multifunctional properties. In this work, we report the electronic, optical, and magnetocaloric properties of the novel material (C₆H₁₀N₂)₂[Co(H₂O)₄P₂Mo₅O₂₃].6H₂O. First principle calculations based on the density functional theory (DFT) have been performed using full-potential linearized augmented plane waves (FP-LAPW). The crystals of (C₆H₁₀N₂)₂[Co(H₂O)₄P₂Mo₅O₂₃].6H₂O with triclinic structure were characterized by X-ray powder diffraction (XRD). The profiles of the density of states (DOS), the optical spectra including the real and imaginary part of the dielectric function, and the measured magnetocaloric properties were presented and analyzed in detail. The results found are in agreement with experimental measurements. As pertinent results, the compound presents a high absorption coefficient in the visible range. A systematic analysis of the experimental and theoretical results shows a good bandgap, a high optical property, and a low magnetocaloric effect which reveals promising original material in optoelectronic, and photovoltaic applications.     

小型N_2-CH_4膨胀机天然气液化流程影响因素分析

利用HYSYS对小型N2-CH4膨胀机天然气液化流程进行模拟,分析关键参数对流程性能(比功耗、液化率)的影响。结果显示:降低制冷剂高压压力、LNG储存压力、制冷剂中甲烷含量和提高制冷剂低压压力、天然气入口压力,有利于减少比功耗;提高制冷剂高压压力、LNG储存压力、制冷剂中甲烷含量和降低制冷剂低压压力、天然气入口压力,有利于提高天然气液化率。     

Theoretical studies of the electronic structures and optical properties of stable blue-emitting polymer based on 4H-cyclopenta-[def]-phenanthrene

Geometries, ionization potentials (IPs), electron affinities (EAs) and optical properties of two series of π-conjugated oligomers (2,6-(4,4-bis(2-ethylthexyl)-4H-cyclopenta-[def]-phenanthrene))_nCPPn (2,6-(4,4-bis(2-ethylthexyl)-8,9-dihydro-4H-cyclopenta-[def]-phenanthrene))_nHCPPn (n = 1-4) were studied theoretically. The ground and the excited state geometries were optimized by B3LYP and CIS methods with 6-31G^∗ basis sets, respectively. The absorption and the emission spectra were calculated by TD-B3LYP method. The lowest-lying absorption is assigned to π → π^∗ transition, and the fluorescence can be described as originating from the ¹[ππ^∗] excited state. IPs, EAs, H-L gaps, absorption and emission properties of PCPP (n = ∞) and PHCPP (n = ∞) were obtained by extrapolation method. The fact that the lowest-lying absorption and the emission of PCPP are blue-shifted compared with those of PHCPP, can be interpreted by the smaller effective repeating units of PCPP. The extra absorption band at 289 nm of PCPP is contributed by the π → π^∗ transition involving the extra π-conjugation CC bond.     

Unveiling the strong coulomb interaction effect on electronic structures and mechanical properties of C4AF

There are works have reported the crystal structures and mechanical properties of ferrite cement (C₄AF) at the atomic scale with deviation owing to the omission of the Coulomb interaction effect (U_eff) between 3d electrons of Fe in C₄AF. In this work, the DFT+U method was used to evaluate its effect on their electronic structures and mechanical properties of C₄AF with two different phases I2mb (C₄AF-I) and Pnma (C₄AF-P). The Fe O bonds of the two phases are all weaker and display U_eff due to the presence of Fe ions. The mechanical properties of C₄AF calculated using DFT+U method significantly differ from those obtained without considering U_eff, in which the former shows lower inferior mechanical properties than the latter. This work presents a comparative study the effect of Coulomb interaction to the internal electronic structures and mechanical properties, which will pave the way for designing high hydration reaction cement and high toughness materials.     

Physicochemical and Theoretical Characterization of a New Small Non-Metal Schiff Base with a Differential Antimicrobial Effect against Gram-Positive Bacteria

Searching for adequate and effective compounds displaying antimicrobial activities, especially against Gram-positive bacteria, is an important research area due to the high hospitalization and mortality rates of these bacterial infections in both the human and veterinary fields. In this work, we explored (E)-4-amino-3-((3,5-di-tert-butyl-2-hydroxybenzylidene)amino) benzoic acid (SB-1, harboring an intramolecular hydrogen bond) and (E)-2-((4-nitrobenzilidene)amino)aniline (SB-2), two Schiff bases derivatives. Results demonstrated that SB-1 showed an antibacterial activity determined by the minimal inhibitory concentration (MIC) against Staphylococcus aureus, Enterococcus faecalis, and Bacillus cereus (Gram-positive bacteria involved in human and animal diseases such as skin infections, pneumonia, diarrheal syndrome, and urinary tract infections, among others), which was similar to that shown by the classical antibiotic chloramphenicol. By contrast, this compound showed no effect against Gram-negative bacteria (Klebsiella pneumoniae, Escherichia coli, and Salmonella enterica). Furthermore, we provide a comprehensive physicochemical and theoretical characterization of SB-1 (as well as several analyses for SB-2), including elemental analysis, ESMS, ¹H and ¹³C NMR (assigned by 1D and 2D techniques), DEPT, UV-Vis, FTIR, and cyclic voltammetry. We also performed a computational study through the DFT theory level, including geometry optimization, TD-DFT, NBO, and global and local reactivity analyses.     

基于降雨过程理论分析的初期雨水调蓄容积计算

以我国现行规范的极限强度理论为基础,从雨水管道设计流量公式出发,考虑到初期降雨强度的时间变化,将一场雨划分为两场雨,推求了一场降雨的收集调蓄过程中初期雨水和洁净雨水累积量的变化规律,并给出在某重现期下的计算公式。     

A computational investigation on the molecular structure,electronic properties and intramolecular hydrogen bonding interaction of 1,1,1-trifluoro-4-mercaptobut-3-ene-2-thione in ground and electronic excited state

The hydrogen bond (HB) strength, geometry optimization, vibrational frequencies and several well-established indices of aromaticity in 1,1,1-trifluoro-4-mercaptobut-3-ene-2-thione and its 15 derivatives in two positions, R1 and R2, have been investigated by means of the density functional theory (DFT) method with 6-311++G** basis set in the gas phase. The obtained results show that the HB strength is mainly governed by resonance variations inside the chelate ring induced by the substituent groups. The following substituents have been taken into consideration: NO₂, SCF₃, Ph, PhOCH₃, SCOCH₃, CH₂OCH₃ and CH₂OH. The strongest S–H···S HBs belong to PhOCH₃-substituted system in both positions, whereas NO₂ and H substitutions in R1 and R2 positions, respectively, produce the weakest S–H···S hydrogen bridges. The excited-state properties of intramolecular hydrogen bonding in substituted systems have been investigated theoretically using the time-dependent DFT method. Natural bond orbital analysis is also performed for a better understanding of the nature of intramolecular interactions. The electron density and Laplacian (?²ρ) properties, estimated by atoms in molecule calculations, indicate that the H···S bond possesses low ρ, positive ?² ρ and H_C<0, which are in agreement with the partially covalent character of HBs.     

VO(H_2PO_4)_2热分析研究

运用ＴＧ、ＤＴＡ,研究了ＶＯ（Ｈ２ＰＯ４）２在流动空气气氛中的热反应行为、非等温反应动力学和热效应。ＶＯ（Ｈ２ＰＯ４）２从６０９Ｋ开始失重,到６９５Ｋ失重完毕,失重率为１４．０１％,失重后的产物为ＶＯ（ＰＯ３）２。运用Ｓｈａｒｐ法、Ｃｏａｔｓ－Ｒｅｄｆｅｒｎ法和Ｄｏｙｌｅ－Ｚｓａｋｏ法对基础实验数据进行分析,推断出该热分解反应机理为成核和生长（ｎ＝１）,动力学函数为Ａｖｒａｍｉ－Ｅｒｏｆｅｅｖ方程;非等温热分解反应动力学方程：ｄα／ｄＴ＝Ａ／βｅ－Ｅ／ＲＴ（１－α）;动力学补偿方程：ｌｎＡ＝０．１８１Ｅ－４．６８ｂ;热分解反应转变热为０．２９１ｋＪ·ｇ－１。