A time-dependent density functional theory investigation of plasmon resonances of linear Au atomic chains

We report theoretical studies on the plasmon resonances in linear Au atomic chains by using ab initio time- dependent density functional theory. The dipole responses are investigated each as a function of chain length. They converge into a single resonance in the longitudinal mode but split into two transverse modes. As the chain length increases, the longitudinal plasmon mode is redshifted in energy while the transverse modes shift in the opposite direction （blueshifts）. In addition, the energy gap between the two transverse modes reduces with chain length increasing. We find that there are unique characteristics, different from those of other metallic chains. These characteristics are crucial to atomic-scale engineering of single-molecule sensing, optical spectroscopy, and so on.

Time-dependent density functional theoretical studies on the photo-induced dynamics of an HCI molecule encapsulated in C60 under femtosecond laser pulses

By using first-principles simulations based on time-dependent density functional theory, the chemical reaction of an HCl molecule encapsulated in C60 induced by femtosecond laser pulses is observed. The H atom starts to leave the Cl atom and is reflected by the C60 wall. The coherent nuclear dynamic behaviors of bond breakage and recombination of the HCl molecule occurring in both polarized parallel and perpendicular to the H-Cl bond axis are investigated. The radial oscillation is also found in the two polarization directions of the laser pulse. The relaxation time of the H-Cl bond lengths in transverse polarization is slow in comparison with that in longitudinal polarization. Those results are important for studying the dynamics of the chemical bond at an atomic level.

Theoretical Study on the Optical Properties for 2,7- and 3,6-Linked Carbazole Trimers by Time-dependent Density Functional Theory

Electronic properties, such as HOMO and LUMO energies, band gaps, ionization potential （IP） and electron affinity （EA） of 2,7- and 3,6-1inked carbazole trimers, two conjugated oligomcrs with different linkages of carbazole, were studicd by the density functional theory with Becke-Lee-Young-Parr composite exchange correlation functional （B3LYP）. The absorption spectra of these compounds were also investigated by time-dependent density functional theory （TD-DFT） with 6-3 IG＊ basis set. The calculated results indicated that the HOMO and LUMO of the 2,7- and 3,6-1inked carbazole trimers are both slightly destabilized on going from methyl substitution to sec-butyl substitution. Both IP and EA exhibit their good hole-transporting but poor electronaccepting ability. The presence of alkyl groups on the nitrogen atoms does not affect the intra-chain electronic delocalization along the molecular frame. Thus no significant effect on the band gap and absorption spectra of compounds has been found.

Theoretical investigation on the excited state intramolecular proton transfer in Me_2N substituted flavonoid by the time-dependent density functional theory method

Time-dependent density functional theory（TDDFT） method is used to investigate the details of the excited state intramolecular proton transfer（ESIPT） process and the mechanism for temperature effect on the Enol＊/Keto＊emission ratio for the Me2N-substited flavonoid（MNF） compound. The geometric structures of the S0 and S1 states are denoted as the Enol, Enol＊, and Keto＊. In addition, the absorption and fluorescence peaks are also calculated. It is noted that the calculated large Stokes shift is in good agreement with the experimental result. Furthermore, our results confirm that the ESIPT process happens upon photoexcitation, which is distinctly monitored by the formation and disappearance of the characteristic peaks of infrared（IR） spectra involved in the proton transfer and in the potential energy curves. Besides, the calculations of highest occupied molecular orbital（HOMO） and lowest unoccupied molecular orbital（LUMO） reveal that the electronegativity change of proton acceptor due to the intramolecular charge redistribution in the S1 state induces the ESIPT. Moreover, the thermodynamic calculation for the MNF shows that the Enol＊/Keto＊emission ratio decreasing with temperature increasing arises from the barrier lowering of ESIPT.

Reconstruction of Probability Density Function for Gamma Distribution

The probability distributions of small sample data are difficult to determine,while a large proportion of samples occur in the early failure period,so it is particularly important to make full use of these data in the statistical analysis.Based on gamma distribution,four methods of probability density function(PDF)reconstruction with early failure data are proposed,and then the mean time between failures(MTBF)evaluation expressions are concluded from the reconstructed PDFs.Both theory analysis and an example show that method 2 is the best evaluation method in dealing with early-failure-small-sample data.The reconstruction methods of PDF also have certain guiding significance for other distribution types.

The Effects of Oxidation States and Spin States of Chromium Interaction with <i>Sargassum Sp</i>.: A Spectroscopic and Density Functional Theoretical Study

The study of various oxidation states of chromium with Sargassum sp. is of particular interest since hexavalent chromium is reduced to trivalent chromium in an aqueous solution. In this study, a systematic density functional theory (DFT) calculations were performed to study the interactions of transition metal chromium ion with different oxidation states and spin states with the Sargassum sp. decorated with carboxylate (acetate) at the wB97XD/6-311++ G(d,p) level of theory. The structures and binding energies of chromium metal-carboxylate complexes at various oxidation states and spin states in gas phase were examined. The coordination strength of Cr(VI) with the acetate ligand was predominantly the strongest compared to the other oxidation states. Vibrational frequency analysis, for the homoleptic monomers of tris [CrIII(AC)3]0 and [CrVI(AC)3]3+ complexes, illustrate good harmony with the experimental and theoretical calculated frequencies. Using the time-dependent DFT (TD-DFT) at the level of CAM-B3LYP/6-311++G(d,p), the vertical excitation energies were obtained. The stabilization energies derived using the second order perturbation theory, Eij(2), of NBO analysis confirmed the greater charge transfer for the observed trends in the metal binding. The calculated binding energies (ΔE) and interactions energies SEij(2) favor the formation of [CrVI(AC)3]3+ complexes. The findings of this study identify efficient electronic factors as major contributors to the metal binding affinities, with promising possibilities for the design of metal-ligand complexes and sensing of the metal ions.

Investigation of Structural and Electronic Properties of [Tris(Benzene-1,2-Dithiolato)M]^3-(M = V, Cr, Mn, Fe and Co) Complexes: A Spectroscopic and Density Functional Theoretical Study

In this study, the first raw transition metals from V to Co complexes with benzene-1,2-dithiolate (L2-) ligand have been studied theoretically to elucidate the geometry, electronic structure and spectroscopic properties of the complexes. Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) methods have been used. The ground state geometries, binding energies, spectral properties (UV-vis), frontier molecular orbitals (FMOs) analysis, charge analysis and natural bond orbital (NBO) have been investigated. The geometrical parameters are in good agreement with the available experimental data. The metal-ligand binding energies are 1 order of magnitude larger than the physisorption energy of a benzene-1, 2-dthiolate molecule on a metallic surface. The electronic structures of the first raw transition metal series from V to Co have been elucidated by UV-vis spectroscopic using DFT calculations. In accordance with experiment the calculated electronic spectra of these tris complexes show bands at 522, 565, 559, 546 and 863 nm for V3+, Cr3+, Mn3+, Fe3+ and Co3+ respectively which are mainly attributed to ligand to metal charge transfer (LMCT) transitions. The electronic properties analysis shows that the highest occupied molecular orbital (HOMO) is mainly centered on metal coordinated sulfur atoms whereas the lowest unoccupied molecular orbital (LUMO) is mainly located on the metal surface. From calculation of intramolecular interactions and electron delocalization by natural bond orbital (NBO) analysis, the stability of the complexes was estimated. The NBO results showed significant charge transfer from sulfur to central metal ions in the complexes, as well as to the benzene. The calculated charges on metal ions are also reported at various charge schemes. The calculations show encouraging agreement with the available experimental data.

基于EOF-DBSCAN-GRU的分布式光伏集群出力预测方法研究

提出一种基于EOF-DBSCAN划分集群的改进统计升尺度的光伏集群出力预测建模方法。针对传统统计升尺度方法子集群中光伏电站出力特性不一致问题,通过皮尔逊相关系数和经验正交函数(EOF)优化特征空间,再根据密度聚类模型(DBSCAN)对区域内光伏电站划分集群,从而增强光伏电站聚类后集群出力特性的一致性。针对待预测日权重系数时间序列动态特性的提取、预测问题,提出一种基于动态时间规整(DTW)的相似日选取算法。最后利用循环神经网络(GRU)模型进行光伏电站出力预测。实验表明该集群预测方法的平均误差百分数(MAPE)约为6.33%,均方根误差(RMSE)约为13.93 kW,均方误差(MSE)为194.25 kW,通过实际光伏电站数据证明了所提方法的准确性和有效性。

几种常用水声信号的特性研究

水声信号是水下导航定位通信的主要信息载体,对其特性进行研究尤为重要。水声常用信号主要有连续波信号、线性调频信号和双曲线调频信号,研究了这三种常用信号的时域、频域以及功率谱波形,对它们的模糊函数、模糊度、模糊函数ξ=0和τ=0截面进行了计算,研究了这三种信号的自相关函数及小波时频分析,研究结果表明实验结果与理论值符合较好。

三碘甲状腺素团簇结构与光谱性质的密度泛函理论研究

我们利用密度泛函理论(DFT),在B3LYP/Lan12mb基组水平上,得到了三碘甲状腺素团簇的几何和电子结构.在此基础上,利用含时密度泛函理论(TDDFT),使用相同的基组和采用极化连续介质模型(PCM),对其溶剂效应下的吸收光谱进行研究.研究结果表明,优化所得三碘甲状腺素团簇的对称性为C1;在基态稳定结构基础上,研究了该分子的红外和拉曼分子振动谱特性,同时研究了其输运性质,即三碘甲状腺素团簇为p型输运材料;通过含时密度泛函理论,在优化好的基态结构基础上,又计算了它的溶剂效应,进一步得出该分子在水溶剂中的吸收光谱特性.

肉桂酸衍生物的太赫兹光谱及弱相互作用分析

利用太赫兹时域光谱技术(THz-TDS)测试了对羟基肉桂酸(PCA)、反式-2-羟基肉桂酸(OCA)和4-氟肉桂酸(4-FCA)三种肉桂酸的衍生物(CADs)在0.5~3.5 THz范围内的吸收峰。基于密度泛函理论(DFT),借助振动模式自动关联判定方法(VMARD)对三种样品THz吸收峰的来源进行了指认。最后采用分子力场能量分解法(EDAFF)分析了分子体系的弱相互作用力形式,通过VMD绘制原子着色图进行了可视化分析,并研究了其原子在分子体系中对弱相互作用力的贡献类型和强弱。研究结果表明,基于THz-TDS、DFT与VMARD、EDA-FF方法结合不但能有效地辨别同分异构体及结构近似的有机分子,而且也能为其生化功能揭示提供有价值的参考数据。

有机给体-受体结构光诱导过程的非绝热动力学模拟:方法与应用

有机太阳能电池的核心组成是有机给体-受体(donor-acceptor,D-A)结构.探究有机给体-受体结构的光激发后的动力学过程对设计新型有机太阳能电池非常重要.非绝热动力学模拟是研究该过程的重要理论方法.然而,相比于小分子体系,有机给体-受体结构通常较为复杂,计算量大,难以采用高精度的非绝热动力学模拟方法.为了克服这一困难,介绍了课题组所发展基于线性响应-含时密度泛函(LR-TDDFT)理论的非绝热动力学模拟方法,通过结合多种分析方法,可以有效的探究有机给体-受体结构光诱导的动力学过程,如电荷转移过程\,能量转移过程\,激子动力学等.该方法不仅可以用于解释现有的实验结果,还可以为后续设计新型有机给体-受体结构提供帮助.

老年股骨粗隆间骨折患者术后髋关节功能的影响因素分析

目的探讨老年股骨粗隆间骨折患者股骨近端防旋髓内钉(proximal femoral nail antirotation,PFNA)术后髋关节功能的影响因素。方法选择2020年1月至2023年1月山东省文登整骨医院行PFNA术的老年股骨粗隆间骨折患者176例,根据术后6个月随访时Harris髋关节评分情况分为髋关节功能恢复良好组和不良组。采用多因素logistic回归方程分析影响老年患者PFNA术后髋关节功能的因素。结果176例患者中男96例、女80例;年龄66~85岁,平均(75.8±4.1)岁。176例患者术后Harris评分为(92.3±3.7)分。PFNA术后6个月,髋关节功能恢复良好124例(70.5%)。多因素logistic回归分析结果显示,术前骨密度<-2.5 SD(OR=3.117,95%CI:1.260~7.710,P=0.014)和术后开始负重时间>7.7 d(OR=2.519,95%CI:1.061~5.980,P=0.037)的老年股骨粗隆间骨折患者术后髋关节功能恢复较差。结论老年股骨粗隆间骨折患者术前骨密度降低和术后负重时间延长是影响术后功能恢复的危险因素。建议加强老年患者术前骨密度筛查力度、改善骨质疏松程度,并重视术后早期的负重锻炼和指导。

Coexistence of Spin Density Wave (SDW) and Superconductivity in Ba_1-xK_xFe₂As₂

With the use of a model Hamiltonian and retarded double time green’s function formalism, we obtain mathematical expressions for spin density wave and superconductivity parameters. The model reveals a distinct possibility of the coexistence of magnetic phase and superconductivity, which are two usually irreconcilable cooperative phenomena. The work is motivated by the recent experimental evidences of coexistence of spin density wave and superconductivity in a number of FeAs-based superconductors. The theoretical results are then applied to show the coexistence of spin density wave and superconductivity in iron pnictide compound Ba1-xKxFe2As2 (0.2 ≤ x < 0.4).

基于激发态分子内质子转移过程的HBT-OMe分子检测HClO的荧光增强机理

采用密度泛函理论(DFT)和含时密度泛函理论(TDDFT)方法,基于连续介质模型,对HBT-OMe分子及其与HClO反应的产物基态和激发态结构及电荷分布等性质进行研究,优化构型结果表明,HBT-OMe分子不能发生质子转移过程而其产物分子则能发生.红外振动光谱与分子共价作用分析进一步证实产物分子能发生质子转移过程.计算的前线分子轨道结果表明:HBT-OMe分子存在扭曲电荷转移(TICT)过程,最高已占据分子轨道(HOMO)和最低未占据分子轨道(LUMO)电荷密度重叠小导致HBT-OMe分子荧光强度弱,结合产物分子势能曲线发现,产物分子质子转移过程能抑制分子的TICT过程,从而使其荧光强度增强.

晶态PDINH光催化剂基态及激发态的第一性原理计算

为了揭示有机光催化剂激发态性质与其光催化剂性能之间的关系,以PDINH晶体为模型光催化剂,使用第一性原理方法对其基态和激发态进行理论研究。密度泛函计算得知,PDINH晶体的带隙约为1.61 eV,其价带和导带贡献都来自于C和O原子的2P轨道;含时密度泛函计算了PDINH晶体的紫外-可见光谱,使用电子-空穴分析方法对造成可见-红外响应的6种激发态进行分析,确定了激发类型,绘制了电子图、空穴图、电子-密度差分图,并计算了D、Sr、H、t,Ecoul、 HDI和EDI等7种指数。结果显示,晶态PDI的6种激发态虽然激发类型分可为n->π*和π->π*2类,但都属于电子局域激发,不利于电子-空穴分离,导致其光催化性能不理想,与实验结果吻合。

时间敏感网络帧抢占时延的混合概率模型

时间敏感网络帧抢占的时延特性相对复杂,难以用单一的标准概率密度函数分析其随机性。针对时间敏感网络帧抢占时延的随机特性分析问题,对帧抢占机制的工作模式和时延影响因素进行了研究,给出了不同可抢占帧长的分阶段抢占时延解析表达式;利用混合概率模型对帧抢占时延的随机特性进行建模,给出了混合概率模型中各个分量及其权重的产生方法;通过数值仿真分析了帧抢占时延的随机性,以及帧长和链路占用率对时延混合概率模型分量权重的影响。研究成果对时间敏感网络帧抢占仿真模型开发和优化设计具有参考价值。

基于密度泛函理论的沙林毒剂近红外光谱研究

近红外光谱涵盖了有机分子中C—H,N—H和O—H等含氢基团的倍频和合频产生的光谱,提供了分子的结构、组成、状态等信息,是研究有机物含氢基团振动的重要方法,常用于食品、农作物等的定性定量分析。生化领域内所研究对象也都含有氢基团,这些含氢基团吸收频率特征性强,受分子内外环境影响小,近红外光谱特性更稳定,故可用于化学战剂和危险化学品检测。沙林是一种神经性化学毒剂,研究其结构、化学特性及光谱性质时,为保证安全,实验中常用模拟剂样品代替测试,但目前尚无公允的沙林毒剂近红外模拟剂。采用密度泛函理论(DFT),基于Gaussian程序包,利用B3LYP/def2-SVP对沙林分子进行基态结构优化,计算了沙林分子的精细结构和分子基频振动模式,引入广义二阶微扰理论(GVPT2)建立了模拟生化毒剂近红外光谱的理论模型,得到近红外振动峰与主要振动模式,由倍频(Overtones)和合频(Combination Bands)振动绘制得到近红外光谱。对沙林在近红外区域内的含氢基团进行解析,对其特征峰进行指认,得到沙林分子在1150、1362和1500 nm处的三个特征峰及其振动模式,其中1150 nm峰是由多个倍频和合频的组合振动贡献产生;1362 nm是一个较宽的吸收振动峰,主要由分子中与C原子相连的原子合频和其他的非C,H原子产生的倍频或合频引起的;1500 nm位置的近红外振动峰主要由C8相关的振动模式贡献产生。通过密度泛函理论建立沙林的近红外光谱理论模型,通过实验验证了其理论模型的可行性,为寻找其近红外光谱模拟剂提供理论支撑。

异烟肼-烟酰胺-丁二酸三元共晶的振动光谱检测与分析

药物共晶是指将活性药物成分(API)与共晶形成物以非共价键的形式组合在一起,形成具有特殊晶胞结构的晶体。共晶可以在不改变API药理性质的情况下有效改善其理化性质,近年来被大量报道。三元共晶指由三种组分构成的晶体,相较于传统的二元共晶,三种组分形成的结构更加复杂,分子间的氢键形式更加多样,合成和分析的难度都大大提高。采用溶剂蒸发法制备了异烟肼-烟酰胺-丁二酸三元共晶,并通过太赫兹时域光谱技术(THz-TDS)对其进行定性分析,证实了可以通过此种方法制备共晶。同时为研究共晶中的氢键合成元形式,结合密度泛函理论(DFT)对共晶中可能的氢键形式进行了模拟,模拟结果与实验结果较为吻合。在此基础上,对三元共晶的氢键合成元形式和振动模式进行了分析。